WATERBORNE

A WATERBORNE MEDIUM is a colorant  mixed  with  a binder suspended in water. The type of binder used  defines  the  type  of  waterborne  medium,  or  waterborne paint. Tempera, for example, is a  waterborne  paint whose binder is egg. Ink is a waterborne medium for a pigment or dye with a shellac binder.  Acrylics  and  vinyls are waterborne paints that have a polymer binder. Watercolor is a waterborne paint with a  gum  binder.  The common element is that after the water evaporates, the binder holds the colorant to the applied surface. The primary advantage of waterborne paints and media is the  immediacy  of  the results. In most cases, a finished drawing or painting can be had within minutes. The major drawback is that most artwork produced with waterborne paints  or media is less durable and has to be protected from such hazardous atmospheric conditions as humidity and pollution, and from physical damage caused by han­ dling and storage.

 

The History and Manufacture of Watercolor

Although through the use of watercolors dates back to prehistoric times, it was not until about A.D. 500 that watercolor painting came to  be considered  a fine  art, when Chinese poet-painters helped it evolve from being primarily a decorative craft. In the West, Albrecht Durer (1471-1528) has been credited with upgrading the level of watercolors. Primarily a printmaker, he was looking  for  a  way  to color areas of his prints and ended up using a combination of transparent and opaque (gouache) watercolors to produce colored drawings. Chalk  was  often added to a watercolor to give a stronger and fuller quality. This explains  the flat and linear appearance of his watercolors, since opaque watercolors do not readily lend themselves to shading.

J. M. W. Turner (1775-1851) was a technical innovator who took full advan­  tage of the newly developed synthetic mineral pigments  that were beginning  to find their way into the artist's palette. He applied these new  transparent  and  opaque watercolors with sponges, rags, and knives, as well as with brushes.  Despite his use of opaque color and even pastel on his watercolor paintings, he is  still  considered   part  of  the  original  English  (transparent)  watercolor  school,. The French Impressionists who followed the English school developed an even more dramatic look by taking advantage of the now numerous synthetic mineral pigments, and by often applying them unmixed.

Today, watercolor is still heavily dominated by the principles of the English watercolor school. Consequently, the term "watercolor" has come to mean trans­ parent watercolor and opaque watercolor is now called "gouache." Modem watercolors are manufactured  by first preparing  a mill-base,  which  is a mixture of raw pigment in gum arabic and wetting agent, as well  as a plas­ ticizer, such as glycerin, to help keep the  color  from  drying  out  too  rapidly. Gum arabic is a thick resin obtained from the acacia  tree.  It  comes  in  small pieces which are tied in cheesecloth and soaked overnight in water to produce a gum solution. It is important that the pigment in the mill-base be uniformly dispersed, or the next step of grinding will be adversely affected.

A base-paint will be produced by grinding the  mill-base  with  additional medium (gum arabic) in a series of rollers,  which  may  be made of  iron,  stone,  or ceramic, or some combination of these three. It is said that too much grinding reduces the brilliance of a color, but too little grinding can produce a gritty consistency. Each pigment has different grinding requirements, and how well a manufacturer accommodates these requirements plays a large role in determining the quality of the final product. Most manufacturers use primarily iron rollers, reserving stone grinding for the most delicate pigments.  The Schmincke  Com­ pany is the only major paint manufacturer to use  the  extra-hard  Diabas  stone mills for all its colors, which is an expensive method of production. Holbein effectively uses a combination of iron, stone, and ceramic rollers to get the best from both the Old World technique and modem technology.

The mill-base is first ground by iron rollers, then stone, then ceramic, which gives an increasingly finer dispersion. The specific number of revolutions and the pressure required for each pigment are considered trade secrets.

At this point, the base-paint may need some adjustments so that the color matches previously established standards. This is done during the last stages of grinding when the paint is ground an additional two to three times to mix in antiseptic and antifungal agents. The paint is then inspected and aged before packaging.

Watercolor pencils and crayons, which have long been in use among  illus­ trators and graphic artists, have recently become popular among fine artists. For­ tunately there are several brands that claim  lightfastness, such as those produced  by Derwent and by Caran D'Ache of Switzerland. They qualify as waterborne media since they can be drawn with and then reworked with a brush and water, applied to a  wet  surface,  or  mixed  with  water  and  then  applied.  (For  more  infor­ mation about crayons and colored pencils,)

Pigments In Watercolor

A Watercolorist should not only have an understanding of the quality of  his or her paints but should also have a working knowledge of the compatibility of the pigments used and the effect air pollution may have on their stability. The pig­ ments in watercolor do not possess a protective coating as oil  paints do;  there­  fore some pigments can react chemically with one another, as well as with air pollutants. This lack of a coating means that dye-pigments, which by their nature tend to bleed and stain the painted surface, are a greater problem  with  water­ colors because they can stain not only the paper but the brush and palette.  All  these factors make it imperative that you understand  the  working  characteristics of colors that you wish in your palette. You should consider avoiding chrome colors in watercolor because they contain lead, which can react  with  the air pollutant sulfur dioxide  and blacken. And, if you are going to rework painted areas frequently, you may wish to avoid dye-pigments, which can stain permanently, and select primarily mineral pigments, which will not.

 

As WITH OIL PAINT, there are three grades of watercolor-artist, amateur,  and student. Since watercolors are used in smaller quantities and bought in smaller volumes than oil paints or acrylic emulsion paints,  the overall  expense of setting up and maintaining a palette of colors is often considerably less than with other media. Most professional watercolorists purchase primarily artist-grade materials, and students purchase artist and amateur grades as funds  permit.  Thus the aver­ age watercolorist often has higher-quality paints than do painters who work in other media. It is  important,  however,  to  see  watercolor  paints in perspective. In watercolors, the quality of the paint is not as important as the quality of the brush or the paper. Each  medium  has its own set  of  priorities.  With oil paints, the paint comes first. In drawing, paper has the highest priority. Without a good brush and paper in watercolor painting, the only thing that will be expressed in the finished product will be the artist's inability to do watercolor  paintings. Because a quality brush is usually more expensive than an entire palette of watercolors, it is often the first item to be compromised when setting up for watercolors. If funds are still short after the brush has been compromised,  the paper, which is used up quickly, is next to be short-changed. Over  the  years, I have seen many painters set up for watercolors in this way only to become discouraged when nothing seemed to work until they changed their priorities.

 

Transparent Watercolor

It is the combination of technique with  the relative transparency  of  the paint that gives watercolor its great range, from  the subtle to the dramatic.  The Eng­ lish watercolor style is a good example of this. Those who paint in this style use transparent washes of color, which allow the background to shine through as if it were another color. The use of textured paper (see Paper, allows flecks of the white surface or previously applied color to show through, giving depth and contrast to subsequently applied colors.

William Reeves, the English color manufacturer, is credited with inventing the dry cake form of transparent watercolor around 1780. These colors were  made from dry pigments, gum arabic, and sugar (which  kept  them  moist)  and  were then fitted into small pans which were set into paintboxes. Although they were considered to be an improvement over the colors then in use (which were sold in sea shells), they still tended to be too dry  and hard,  with  a  tendency  to crumble. A moister cake was created  by  the French,  who substituted  honey  for the sugar in the original formula. In 1830, the  English  replaced  honey  with  glycerin, which is still in the formula used today. The first watercolors in tubes were introduced in 1846 by Winsor & Newton, who now makes more  than  eighty colors in tubes.

 

WATERCOLOR DYES

Watercolor dyes, such as those produced under the names Dr. Martin's or Lumacolor, are somewhere between a watercolor and an ink. They are made primarily from dyes rather than from pigments or dye-pigments. They  are  designed primarily for the graphic artist, whose needs  are  convenience  and intense color, even at the sacrifice of permanency. With the exception of a few colors, watercolor dyes are highly fugitive and aie not for use in fine art.  Colors that are fade-resistant are marked as lightfast. However, changes in acidity and alkalinity can significantly alter the appearance of virtually any watercolor dye, lightfast or not.

 

The first watercolors were opaque and were referred to  as  "body  color." Exactly how body  color took on the  French  name "gouache"  has  been a matter  of speculation for some two hundred years. The LeFranc & Bourgeois Company says, "The word 'gouache' comes from the Italian guazzo, which  means  the mixing of water, glue, and pigments."

Today, opaque watercolor is known as gouache, poster  paint,  designers' col­  ors, and tempera. The terms "tempera" and  "poster  paint"  are  used  for  the  lesser qualities of opaque watercolor, which are not acceptable for fine artwork. Gouache and designers' colors are acceptable for fine artwork with certain reser­ vations. Almost all the commercially available gouache is made more for use by illustrators and designers, for whom having a particular color sometimes out­ weighs permanency. It is not unusual to find a considerable number of fugitive colors offered in lines of gouache, and these must be avoided by the fine artist. Gouache also has other drawbacks.  If,  for example,  it is applied  too  thickly,  as is done in acrylic or oil painting, it will tend to crack. The use of  a rigid support will improve, but not correct, the problem. Bleeding and staining of colors are  more common in gouache because of the  greater  percentage  of  dye-pigments used in its manufacture.

Gouache is made in  much  the same  way as transparent  watercolor.  However, it is rarely ground as finely and has a much lower concentration  of  pigment because of the addition of white and other additives, which are designed  to improve leveling properties and slow the rate of  drying.  Gouache  is made  this way to allow the artist to apply a flat, opaque field of color with a minimum of dilution or mixing and to achieve a look very different from watercolor.

There seem to be three types of gouache on today's market. The first places emphasis on opacity, even to the extent of limiting the color range. Winsor & Newton's Designers Gouache is an example of this. There are some  seventy  colors, with several grays, blacks, whites, and  a  gold  and  a  silver,  most  of which are quite opaque. LeFranc  & Bourgeois's  Designers'  Gouache  is an example of  the second type, where  the emphasis  is on  color  range rather  than  opacity.  It manufactures fifty-four more colors than Winsor & Newton, in addition to the several whites and blacks, but the paints are, on the average, slightly less opaque.

In the last type, quality dominates both color range and opacity. The German company H. Schmincke, recently reintroduced in the United States after a long absence, makes a line of double  stone-ground  gouache  of  the  same  quality  as its extra-fine artists' watercolors. This paint is very  finely  ground  and  is  more like the original gouache formulations intended for fine art. The information in Schmincke's color chart indicates that only the most permanent pigments availa­  ble are used. This gouache is so fine that it is rated to be  used  in a  0.3mm airbrush without clogging (recent tests show that it works just  as  well  in  a  0.1mm airbrush).

 
Media for Watercolor

Watercolor depends on the absorbency of the working  surface  and  on  the  binder to remain where it is applied. If the surface is not absorbent, like glass or plastic, watercolor will crawl (an art term for the beading of water on nonabsor­ bent surfaces), rub, or flake off  the surface.  If  very  dilute  watercolor  is applied to a semiabsorbent surface, like a plate-surface bristol paper, there could  be so  little binder that the watercolor might dust off the way a pastel drawing might.  If  an absorbent paper, like a print paper, is used, the watercolor often spreads uncontrollably or sinks below the surface. The purpose of watercolor media is to regulate watercolors so that they can be controlled within a particular working situation, as well as to create special effects.

 

GUM ARABIC

Gum arabic is the binder for  watercolor.  It is also frequently  used  as a  medium to help keep diluted watercolors from sinking below absorbent surfaces, to give a crisp appearance to the edges in a watercolor, to increase transparency, and to provide a varnishlike surface. Gum arabic is a natural gum, which is collected in  the  form  of  an  exudate from branches of an African tree of the species acacia. The best gum arabic is collected from commercial plantations  in the Sudan. The quality  of gum arabic  can be simply tested by dissolving some of the dry form in water, which should leave very little or no residue. The addition of a drop of iodine will indicate any added sugar (used as filler) by leaving a purplish color.

A gum arabic medium can be prepared by  adding one part dry gum arabic  to two parts water and then slowly boiling until the gum is dissolved.  A  small amount of camphor (moth flakes) added to the medium will help to preserve it. Commercially prepared gum arabic media often have an emulsifier and glycerin added to improve  handling.  A  thicker  watercolor  medium-a  gel-can  be  made by the addition of silica.

 

GUM WATER

Gum  water  is the  name given to a diluted  gum arabic  medium  that has a wetting agent. This medium allows for the addition of smaller amounts of gum for improving the transparency without decreasing the watercolor's ability to flow on the working surface. It is the  wetting  agent  that  prevents  crawling,  or beading, on less absorbent surfaces.

 

AUXILIARY PRODUCTS FOR WATERCOLOR

The following products are used to change, or control, the  handling  char­ acteristics of watercolor.

Ox Gall 

Ox gall that has been clarified is a natural wetting  agent for  watercolors.  It is used to reduce the surface tension between a watercolor and a less absorbent surface. However, only small amounts should be  used  and  some  caution  is needed when using ox gall with colors that are made from pigments such as ultramarine blue, which are sensitive to acidity. 

 

Prepared Size 

Prepared Size is a product of Winsor & Newton Company. It is made  from gelatin, water, and a preservative. The manufacturer describes it as "a soft gel  which reduces the absorbency of paper, boards, and lightweight textiles. The gel becomes liquid on warming. Thinning is not normally  required." This  prepara­  tion achieves the opposite effect of that obtained with ox gall.

Wetting Agents.

Wetting Agents for Nonabsorbent Surfaces are commercially prepared and include Flex-opaque and No-Crawl, which are used primarily to allow the appli­ cation of gouache on such nonabsorbent  surfaces as clear  polyesters  and acetate. A small amount-a drop or two-added to a watercolor mixture will improve flexibility and help prevent flaking. However, if too much is added, the paint becomes tacky and will not dry properly.

Masking Fluids.

Liquid Friskets or Liquid Friskets, are like pigmented  rubber cement. They  can be painted on an area in which you wish to block the application of a watercolor. After the masking fluid is applied and has dried it will protect the surface, and when it is no longer needed it  can  be  rubbed  off  easily.  Luma Mask, Art Maskoid, Art Masking Fluid, and  Miskit are some of the brand  names for this pigmented rubber latex solution. These products should not be thinned or applied to a wet surface.

 

Egg Tempera

The term "tempera" comes from temper or tempering, which means to bring something to a desired, or usable, consistency. In this case, the something is a pigment. Egg tempera is one of the oldest, most versatile, and most durable methods of painting. Said to date back to prehistoric times, it is  generally unaffected by humidity and temperature changes. Tempera emulsions form their own protective surface film and do not darken with age  as oil  paint  films do. They dry rapidly and become water-resistant, which means one  application  of paint can be rapidly followed with another without the two layers mixing. This unique property is a distinct advantage  over  ordinary  watercolor  in  that a  wash of a different color may be applied over the original color without the two colors mixing to form a third. This allows you  to see  one color  through  the other.  In  egg tempera, a red wash may, for example, be applied over a blue  wash, and the result will be a blue-red or violet, whereas the result of this procedure in watercolor will tend to appear as a muddy brown.

Tempera colors can be scraped off easily and reworked. When applied in thin layers the results are more transparent than transparent watercolor; when applied more thickly the results are opaque like gouache. After the tempera painting is completed, it can be burnished (polished) with an agate to add depth and  bril­ liance and to increase transparency, or it can be varnished to look like an oil painting.

The first recorded recipes for egg tempera called for only the egg whites and were used for illuminating manuscripts on paper and parchment. Because this mixture is brittle, it was eventually replaced  by  a recipe  that required  only  the egg yolk, which contains semidrying oils and produces a tougher, more flexible paint film. This recipe was prevalent with the Byzantine artists  of  the thirteenth and fourteenth centuries. In the fifteenth century, with the development of oil painting, egg-oil emulsions came into use. Soon after, egg tempera took second place to oil paints and became just  a  convenient  medium  for  underpainting before the application of oil paints. Many of the old masters used a green earth tempera color underpainting in their oil paintings to create more realistic flesh tones.

Egg tempera paints are made by mixing powdered pigments with egg yolk in roughly equal parts. The  pigment  is first made into a paste  with  a small  amount of water. (Some pigments, such as alizarin crimson, Prussian blue,  and  some blacks do not mix readily into a water paste and so a small amount  of  alcohol  must be added as a wetting agent.) A fresh hen's egg (eggs sold  in most  markets are often several weeks old) and distilled water are used  for  the  binder.  To prepare the binding medium, an egg  is cracked  and  the  yolk  is separated  from the white. The yolk  is dried by  rolling it in  the  hand  or by  placing it on a sheet  of absorbent paper. The yolk is then  cut  with a knife and  the liquid  allowed  to run into a glass jar.  Distilled  water  is added  to bring  the egg  to the consistency of thin cream. The pigment paste is now mixed with the egg yolk binder and the paint is ready for use.

Tempera made with only an egg yolk is not as workable a painting medium  as  an egg-oil emulsion. The addition of a small amount of stand oil improves the handling properties and increases the resistance to cracking so that the paint film can be made thicker. Egg-oil emulsions can be used on flexible supports such as canvas, heavy watercolor paper, and thick bristol paper, if applied in thin layers. Thicker layers, like those used in the application  of  gouache,  are  quite  safe if they are built up slowly in thin layers.  Egg-oil  emulsions  produce  a  glossier finish than pure egg tempera and dry harder. Like egg tempera, an egg-oil emul­ sion dries very rapidly, in seconds in thin washes,  and  can  be  painted  over  almost immediately.

Egg-oil emulsion temperas are now being offered in tubes by the Rowney Company and the Sennelier Company. After thinning with a little distilled water, the paint can be used straight  from  the tube,  saving  the artist  the inconvenience of having to prepare the color from the raw materials before each painting ses­  sion.

You can prepare your own egg-oil emulsions according to the following instructions. But you should take extreme caution when using dry pigments.

Egg Yolk and Linseed Oil are combined to create an egg-oil  emulsion  with  an oil paint consistency. Mix one teaspoonful of oil with  a  single egg  yolk.  Too much oil slows the rate of drying significantly  and  tends  to leave a tacky  sur­ face. One part of this emulsion can then be mixed with one part of  water­ dampened pigment.

Egg Yolk, Stand Oil, and Damar Varnish make a durable and flexible egg-oil emulsion. Mix one egg yolk and one level teaspoonful  of a mixture of  half stand oil and half Damar varnish. Pigment can then be added one part to one part.  As with all egg or egg-oil temperas the surface can be polished with a silk pad

  • when dry. The disadvantage of this egg-oil emulsion is that it very much resem­ bles oil paint with its inherent yellowing; thus it has  little  advantage  over  oil paint. Venice turpentine can, however, be used as a substitute for stand oil, to reduce future yellowing and to improve the clarity of the paint film.

Whole Egg and Linseed Oil is the lazy person's egg tempera.  The egg, oil, and pigment are mixed in equal portions. This egg-oil emulsion dries relatively  quickly, producing a hard, but slightly cloudy, surface.

Casein

Casien is a milk protein which was commonly used by painters in the past as a binder to make a paint with characteristics similar to egg tempera. At one time, casein was a common glue used in cabinetmaking and was know for its great strength. A powdered form of casein is made by drying the curd of soured skim milk (the milk fats from whole milk are nondrying oils and must be removed). Today, casein is prepared commercially by heating and acidifying skim milk and then drying it to produce a powder, which is only soluble in  water  if  made alkaline. One way to prepare a casein solution  is  to  soak  the powder  in  water and then add calcium hydroxide, which can be purchased  from a chemical  sup­  ply company. Fortunately, most casein powder, when it  can  be  found,  is in  a form that will mix readily with water.

The use of casein is said to date back to the Egyptians. It was also used as an alternative to rabbit-skin glue for sizing canvas because it could be applied cold. The first commercially produced casein was marketed in the nineteenth century. The Pelikan Company of Germany produces casein paint called Plaka, which can be found in most artists' material stores. Its consistency allows for application by either brush or palette knife. It adheres well to paper,  paperboards,  wood, plas­ ter, plastic, glass, and metal. It dries matte with a velvetlike finish and becomes waterproof in twenty-four hours. Outdoor use requires a final, protective varnish. Casein paint has some drawbacks;  although  it  is  highly  water-resistant, it is not truly waterproof, and it is brittle and becomes  more so as it ages. Therefore, the thicker the paint film, the more rigid the support should be. In general, thick applications of casein paint should be avoided. Adding a little drying oil, such as linseed oil, to casein paint will reduce potential  cracking,  but  will slow  the drying time and add some yellowing properties. Casein paints dry very quickly and look like oil paint except that they have a matte finish. The popularity of casein waned with the introduction of polymer  emulsion paints, which have almost all the advantages of casein paint with none of the drawbacks.

Ink

AN INK is a watercolor that is already diluted for convenience  and whose color­  ant tends to remain in solution. An ink is composed of a pigment or dye that is suspended and stabilized in water. Glue, gum arabic, gelatin, shellac with borax, and soap are some of the more common ingredients used to  maintain  a suspen­ sion and provide a binding agent.

The most common form of ink, dating from about 250 B.c. to approximately 1100, was a carbon black ink with a glue or gum binder. At  this  time,  it  was found that the mixing  of  a  natural  iron  salt-ferrous  sulfate-with  an  extract from nutgalls, which are high in tannic acid, resulted in a chemical reaction that produced a blue-black ink. This method of ink production was considered an improvement; however, it was not lightfast and the particles that remained• in the ink from the chemical reaction did nothing  to  improve  flow  characteristics.  It was the development of synthetic dyes, during the nineteenth century, that paved the way for the fountain  pen. Inks could now  be made from true solutions,  with no particles to clog a writing instrument.

 

India Ink

The term "India ink," or "China ink," originally referred  to  a  lampblack  (car­ bon) ink in stick form produced in either China or  Japan.  Today,  "India  ink" refers to any ink made of carbon that is also waterproof. Some manufacturers of India ink still use carbon from Oriental ink sticks. Shellac is commonly  used  as the binder for this ink and makes it waterproof. India ink should not contai

n any dye.

There are two methods of testing an  ink  to see if  it  is a dye  composite.  A drop of ink placed on   piece of absorbent  paper will spread out and feather at the edge. An ink that  is a dye composite  will  produce  a two-colored  edge,  such as  a  blue-black  and  maroon,  within  a  few  hours,   and a carbon   black   ink   will not. The second method is  to place some of  this ink on  paper  in direct  sunlight for one day. If there is any evidence of fading, it is not a carbon ink.

Nonwaterproof India inks are available-they are made primarily for use in fountain pens. The absence of shellac reduces the possibility of clogging. Non­ waterproof India inks always state on the label either "nonwaterproof" or "fount." Only such inks should be used in a fountain  pen.  However,  the  use of any India ink, waterproof or not, will void most fountain pen warranties.

It would seem that the centuries of continuous  use  of  India ink in  both  writing and drawing can be attributed to the simplicity its use  and  its  great  perma­nence.

 

Drawing Inks

The term "drawing ink" refers to both India ink and colored  waterproof  inks. Until recently, colored drawing inks were known for being highly  fugitive.  Today, there are several transparent dye composites, and several semiopaque pigmented inks that are labeled lightfast. These-and only these-may be  con­ sidered for fine artwork, but remember that lightfastness of such products often meets only the minimum standards.

 

Fountain Pen Ink

Conventional fountain pen inks are dyes dissolved in water, or water-alcohol mixtures, with a nonwaterproof binder. This allows the ink  to flow  freely  with­ out clogging the pen. Until recently, almost all fountain pen inks were highly fugitive and could only be preserved by protection from exposure to light. The recent resurgence of interest in calligraphy, combined with the manufacture of calligraphy fountan pens, generated a demand for fountain pen inks, expecially colored inks, that did not fade when the finished product was framed and dis­ played. Today, there are several companies producing a limited range of both waterproof and nonwaterproof and pigmented and dye-composite inks that can be used in fountain pens. However, they are new and should  be used with caution, and only after reading any restrictions described on the label.

 

Inks for Techincal Pens

Permanence, opacity, and being waterproof are high priorities in a technical pen ink. Technical pens, which  are used  in drafting  and illustration,  are designed  to be used with permanent, opaque waterproof ink that  would ruin any other foun­ tain pen. (Technical pens do require some maintenance or they, too, will be rendered useless by such inks.) Inks made for technical pens often  meet  mini­ mum lightfastness standards for fine artwork, and may  be used for such,  if  they are labeled "lightfast."

As the use of  technical  pens has widened, so has the selection of inks for use   in them. Today, transparent and opaque and matte and gloss inks are available. There are also inks that work on plastic  surfaces,  such  as acetate  and drafting film. The flow, or working characteristics, of ink are often very different  from brand to brand. Some inks, like those produced  by  Koh-i-noor  Rapidiograph, seem to be made with density foremost  in  mind,  and  are  not as free  flowing. This quality is ideal for drafting, where exacting reproduction of drawings is required. For fine artwork, however, flow is often more important  than  density, and many other companies produce thinner  inks that  flow  more easily. It is wise to sample several brands  to see Whatever  ink  you select, it should never be used in a fountain pen.

Oriental Inks and Watercolors

All the research on inks and watercolors leads back, again and  again,to China and Japan. Calligraphy itself is the oldest form of abstract art, and water­ color painting developed from it. It would seem almost impossible to master waterborne media without some appreciation for the source of it all. And to appreciate the art of the East is to appreciate  the  nature of its materials,  for they are inseparable. It would also help to understand that the selection of Oriental materials is more subjective than objective. It is possible, for example, to choose from as many as fifty different shades of black,  ranging  from  warm blacks  to cold blacks. all of the same level  of quality.  In such  a case, how could  a choice be anything but subjective-how can one shade be said to be better than another unless it meets your own particular needs or desires?

The best guidelines for the novice are price and previous exposure. With Oriental materials, price is a good indicator of  quality  because,  in  general,  if  it  costs more, it's usually better. Another guideline is not to overbuy. If,  for exam­ ple, you have never before been exposed to ink sticks and ink  stones,  it  is unlikely that you will be able to experience the subtle differences between their levels of quality and you would be wise· to buy conservatively.

 

INK STICKS

In the Orient, ink is found in the traditional form of a solid stick. Liquid  ink is made by rubbing the ink stick against the wet surface of  a  particular  type  of stone. Ink sticks are made by burning either vegetable oils (such as sesame oil, rapeseed oil, and paulownia oil), or pine wood and pine resin and collecting the soot, or lampblack, which is then combined with animal hide  or  bone  glue, spices, and minerals. The mixture is compressed and dried into a stick.

Ink sticks made from vegetable oils tend to produce a warm black ink, with a hint of brown or purple. Calligraphy inks are made primarily from oils and their exact shade is often regulated by the addition of various plant  matter,  as  well as the source of the glue (what type of animal and whether the shin or other bones were used). The plant matter and glue are added to the soot before the stick is molded. A shine is considered a desirable characteristic in  a calligraphy  ink and an undesirable characteristic in an ink for painting. The shine is regulated by the particle size of the soot as well as through the addition of plant matter.

 

Inks made for pamtmg do not contain any additional plant matter  and  the particle size is selected to give a matte appearance, so that the subtlety of the painting can be seen without distraction. Painting inks are made from either vegetable oils or pine. Those made from pine soot produce  a cool,  bluish-black ink, which has a lighter appearance than those made from oil. Pine-soot inks are used for washes as well as for the overall background of a painting.  The darker inks made from oil are used for the final details and for contrast.

When starting or testing a new ink stick, never use the first grind because ink sticks often have a coating that is best removed before  use.  One  method  of  testing an ink is to dilute the freshly ground ink so that it can be used as a wash. Then make a brush stroke where, at some point, you reverse the direction, going over a part of the area previously painted. If the area or edge of the previously painted area maintains its integrity,  it is a good sign. The more it dissolves,  the  less desirable the ink is. Some inks look better while they are still damp on the paper and become dead when dry, while others  look  better  after  drying  than while in use; you should therefore wait until inks are dry to inspect them.

Oriental ink sticks are like wines; their quality is determined as much by the aging process as by method of preparation. An ink stick  should  be aged for  at least one year (two to three years is preferable) before use, and, indeed,  some of  the very best sticks are more than four hundred years old. The aging process involves the natural oxidation of  the  protein  that  makes up the glue.  According to Boku-undo U.S.A., Inc., only ink sticks that are handmade  truly benefit from  this aging process, and for this reason  it  distributes  only  handmade  ink  sticks that have been aged for a minimum of five years. Prices for Oriental ink sticks range from $1.50 to several thousand  dollars  for the  highest-quality sticks  that  are several centuries old.

Chinese Ink Sticks are made primarily from pine trees that are high in resin and therefore characteristically produce a  bluish-black  ink.  However,  there  are always exceptions because the addition of minerals  and spices may change the  hue. The Chinese make ink sticks throughout  the year without regard  to changes  in weather. This, unfortunately, can result in an  ink  stick  cracking  when  it  is later shipped to parts of the world that have dramatically  different  temperatures and humidity. Broken ink sticks can sometimes be repaired by wetting· the two broken ends and holding them together until they dry. Producing ink sticks year round also results in some inconsistencies in quality. The Chinese grade their ink sticks using a series of three-digit numbers.

101-The best professional quality commercially available

102-Very good, professional quality

103-Good, professional quality

104-Amateur

105 or higher-Student

Japanese Ink Sticks are usually made from vegetable oils and therefore tend to produce warmer blacks. But, because so much of Japanese history involves Chi­nese influence, blue-black ink sticks made from pine in Japan are commonly available. Many Japanese ink sticks have camphor added, which gives a silvery black appearance to the ink when it is used full strength. The illusion of silver flecks can be seen when the image is held to the light at an angle.

The Japanese make ink at only one time during the year (in the autumn), to reduce the possibility of cracking and to improve consistency.  Buying  Chinese  ink is always a gamble even when purchasing a second stick made by the same family in China. It could be among the world's best or the world's worst. The Japanese go for consistency, so you may not get the world's  best,  but  you  also will not get the world's worst. They have good, constant quality so the second purchase will be like the first.

The Japanese utilize a series of dots to classify the quality of their inks.  Five dots on the end of the stock indicate the finest quality, while fewer dots signify a lesser quality. Unfortunately, certain Japanese manufacturers sometimes take advantage of the beginner's limited knowledge  in  this area  by  putting  five dots on their lowest-quality sticks and, in some cases, adding blue dye  to ink sticks made from vegetable oils. Price should be some indication of quality.

BOTTLED ORIENTAL INK

In China and Japan, the use of bottled ink is frowned upon and generally consid­ ered to be a concession to barbarians. There are, however, several brands of Oriental ink from China and Japan that come ready for use in bottles. The best is not as good as the ink that comes in stick form, but it is  usually  superior  to Western bottled ink.

Many manufacturers have switched from using animal glues to using acrylic polymers as a binder for the ink. These acrylic inks have a longer shelf  life of seven to ten years, as opposed to the two to three years of inks that have animal­ glue binders. Acrylic inks also tend to be waterproof, rather than water-resistant. Consequently, it is more · difficult to shade an area properly after an acrylic has dried. An acrylic ink can also ruin a brush that is left to dry  in it,  while animal­ glue inks can almost always be redissolved. The better grades of bottled ink are  still made with animal glue.

Ink paste, which is a concentrated  form of liquid  ink, is also manufactured  in  as large a variety as bottled ink. Few stores, however, carry an equal variety.

INK STONES

Natural ink stones are made from slate,  and  imitation  ink  stones are ceramic. The ink stone, with water, is used to grind  the ink  stick  into  tiny  particles to form liquid ink. The better the stone, the smaller and  more consistent the parti­ cles will be and the denser the ink. A good stone will make a  poor ink stick perform slightly better than a good ink stick ground on a poor stone. It is best to have a stone that at least matches or slightly exceeds the quality of the ink stick. The older the stone that is used to make an ink stone, the better  it  will per­ form. Because the geological formations in China are much older than those in Japan, the best stones come from China. Both the Japanese and  Chinese make their best products out of the oldest stone that can be found  in  China.  The Japanese term for the best grades of slate used in the manufacture of ink stones is tankai. There are several grades of tankai just as there are  grades  of  dia­  monds.  The very best tankai  was found under rivers. Today it can only be found in private collections and in museums. Since China has a long history,  all  the stones of this quality have already been found. Today's tankai is collected from caves and these lesser grades of tankai can be found  even  in the West,  but they are expensive. Japanese ink stones that are more moderately priced are made primarily from more recent lava formations. The least expensive ink stones are made from ceramic rather than from natural stone. (For colored ink sticks, mul­ tiple ceramic stones are used because of the expense and to keep the better stone from being contaminated with residual colors.)

Japanese ink stones are made into a rectangular shape with a well, or deeper impression,  on one side to hold the water separate from the grinding surface and   to collect the ink. The better natural stones are often characterized by a natural irregular shape, or are encased in a wooden box.

Chinese ink stones are usually round in shape with either a concave or a flat grinding surface. It is also common  to find  a lid,  which  covers  the stone,  made of wood or of the same stone. The moderately priced stones are made of slate. Better quality is sometimes indicated by the irregular shape, a wooden encase­ ment, and the purplish hue of the stone. Some Chinese ink stones have an oil  or wax on them to help protect them until purchase.  This  material  should  be  washed away before use.

Inspecting an Ink Stone involves looking for  any  hairline  cracks that  may  result in the stone coming apart easily, and checking to  see  if  it  is a  ceramic stone or a natural stone. If there  are  any  natural  imperfections  such  as streaks that appear to run with the tooth,  or grain,  of  the stone,  they are not  necessarily to be avoided and are, in fact, sometimes sought after for the character that they give.

Testing an Ink Stone involves three steps of inspecting the grinding  surface. The finer the surface, the finer and more consistent the quality of the ink will be. The surface of an ink stone is similar to a  saw's  teeth,  in  that  there  are  tiny peaks tilted in one direction that can grind off small particles  of  the ink  stick  when rubbed against it. The first step is to test the tooth of the stone's grinding surface. This can be done by rubbing  the surface of  the ink stone  with the tor edge of a fingernail in a direction away from the well. The better the stone,  the more distinct and uniform the mark will be.

The next test involves the use of water. If the tooth is fine and pointed in one direction, a small amount of water placed on the (clean) grinding surface will  appear to sink immediately just below the surface, but will not appear  dry. The teeth will break the  water tension  and the water  will be trapped  beneath the tips  of the teeth. If the surface where the  water  has been  applied  dries out quickly, then the stone is too absorbent and  of  lesser quality. If  the grain  is irregular  or has imperfections, the absorption will also be irregular.

The final test is to check the flatness and smoothness of the grinding surface. Visual inspection and touching the surface with the fingers  or  tongue  should  show a very smooth and flat surface. Ink stones range in price from three dollars to eighty thousand dollars, depending on quality. A stone of adequate quality can easily be had for between  ten and thirty dollars. A complete inspection should be reserved for the more expensive ink stones. Performing an inspection this thoroughly on an  ink  stone  that is priced  at less than ten dollars, is like using a jeweler's eyepiece  to  inspect  jewelry  at  the  comer drugstore.

 

ORIENTAL WATER COLORS

The major difference between Western watercolors and Oriental  watercolors  is that in the Oriental system some colors are by tradition opaque, and others are transparent. They are sold in the form of a dry cake in a ceramic dish, or in a powdered form where the liquid binder is mixed in with water to make  water­ color, or in colored ink sticks. (Although none of these materials should be considered nontoxic, traditional vermilion ink sticks, because they are made from mercuric sulfide, are highly poisonous and should be used with caution.)

The best Chinese watercolors come in a very limted number  of  colors and  are in the form of little chips that are dissolved in water to make the color. With the exception of these chips, most of the Oriental colors available in this country are not of the first quality. Today, most instructors of Chinese and Tibetan painting who live in the West recommend the use of the finest tube Western watercolors  and gouache over the lesser-quality Oriental watercolors.

 

"NEW EARTH COLORS"

These colors are artificial mineral pigments  made of  glass frits.  They are similar to Egyptian blue in that their color depends on how finely ground the particles of pigment are. The main ingredient is lead borate glass, which is fused into such color-producing agents as metallic cobalt and chrome, and then ground. The  ground glass particles are then separated according to size,  which  also  deter­ mines the color. Holbein makes a line of  these pigments,  which  have been used  in Oriental watercolors and are currently being tested for possible application in Western artists' materials. By employing this method of  manufacture,  they  are able to make as many as two hundred different shades from a few basic colors.

 

SEAL INK

Although seal ink is not a watercolor,  it is used  to sign a piece of calligraphy  or  an Oriental-style painting. A chop, which  is like a  rubber  stamp  made of  wood or bone, has the artist's name or symbols carved  on  the face.  The face  of  the chop is pressed gently into the surface of  the seal  ink  (sometimes  it is necessary to touch the seal ink  several  times to collect enough  ink on  the chop's surface).  In some traditions, the seal is placed so that it just touches the edge of  the still damp ink, or watercolor, because the slight mixing that occurs is impossible to forge, and the original can be proved.

The seal ink container usually has a loose-fitting cover  to  allow  for  a  thin piece of silk to be placed over the ink surface. This piece of material  serves to  keep the surface moist so it can be reshaped through the silk. The best seal ink is made from genuine vermilion from China, which is com­posed of mercuric sulfide and is extremely poisonous.

Polymer Emulsion Paints and Media

An Emulsionis the suspension of tiny solids in a liquid. Milk is an example of an emulsion, and most solids, if made small enough, will tend to remain in suspension. A polymer is a larger molecule made of smaller  and  simpler chem­ ical units most often arranged in a chainlike  formation.  A polymer  emulsion  is the suspension of polymers in a liquid. As the liquid evaporates, the suspended polymer solids come closer together until they touch and combine to form larger chains and eventually a film. A paint can be made by pigmenting a polymer emulsion. The type of polymer used determines the type of paint or  medium­ acrylic polymers for acrylic paints and vinyl polymers for vinyl paints.

Polymer emulsion paints, by comparison  with oil paints and  watercolors,  have a short history, which began in late 1948 with the development  of  polyvinyl acetate emulsion (PVA), commonly known as white  glue.  However,  PVA  was too sensitive to water and heat, and the paints  made from  it  were  not  durable. The acrylic polymer emulsions now used in artists' paints are a byproduct of the attempt to develop a new type of house paint during the early 1950s. (Today, however, the amount of actual  acrylic binder in  house  paint is often  quite  low.  In some states it can be as low as 20  percent  and  still be called  acrylic  paint.  This would be too low to use in fine artwork.) The first artists' acrylic polymer  paint became readily available in North America around  1963  and  in  Europe about two years later.

 

THE MANUFACTURE OF POLYMER EMULSION PAINT

The manufacture of polymer emulsion paints is a balancing act. Mixing  dry pigment directly into a polymer emulsion rarely creates a usable paint. Several additives are needed to produce a workable paint. The polymer solids must be coated with emulsifiers to prevent them from binding together before the liquid evaporates. Dispersants are necessary to keep the pigments that are added from clumping together and/or settling out of the  liquid.  Antifoaming  agents  are needed to prevent foaming during the application of a  paint  so  that  the  dried paint film does not have a craterlike surface. Wet-edge agents, such as ethylene glycol (very poisonous) or propylene glycol (less  effective,  but  nontoxic),  are used to regulate the drying time, allowing sufficient time for mixing and applying the paint. Thickeners are used to transform the milky quality into a paintlike consistency. And last but not least important, a preservative is added.

The type of paint film that is formed depends on the specific polymer formula­ tion used. For example, the Rohm and Haas Company, the supplier of acrylic emulsion to all paint manufacturers in North America and many  parts  of  the world, offers several varieties of 100 percent acrylic emulsion  (of  which 44 and  47 percent of the emulsion is composed of  resin solids).  Rhoplex  is the name it has given to its acrylic emulsion and each formulation  is  assigned  its  own number. The most commonly used emulsions that are dispersed in water are  AC-22, AC-33, AC-34, AC-35, and AC-235. (There are also acrylic  solutions­ such as Acryloid F-10, which is 40  percent  resin  solids  in  mineral  thinner­ which are used in the manufacture of  paint varnishes and  acrylic  paints that can  be thinned with mineral spirits.) AC-22  has good  flow  and leveling  properties, but is less durable than the other formulas. AC-33 was the first formula  used  in  the arts and is still commonly used. AC-34 was designed for  outdoor  use  on wood, but tends to be slightly more brittle. AC-235, the improved version of AC-35, is used to give paint a thicker quality and would be used in impasto painting.

Since each of these formulas has desirable qualities as well as undesirable qualities, most paint manufacturers blend the various polymers like  chefs  to obtain, what is in their opinions, the best working  characteristics.  A  blend  of more than one polymer is referred to as co-polymers;  virtually  all  artist  acrylic and vinyl paints are co-polymers.

The physical process of making acrylics resembles the  process  one  would  more expect to see in a pastry shop than in a paint mill. Some manufacturers  do  not use rollers to grind the paint mixture as would be done with oil paints, but simply mix the ingredients together. Mixed paints are less desirable for airbrush­ ing and for watercolors where fine dispersion is important.

 

CHARACTERISTICS OF POLYMER FILMS AND PAINTS

After the liquid of a polymer emulsion evaporates, such as with an acrylic poly­ mer, a tough waterproof film forms.  Although  the chains  formed  by  polymers are broken by ultraviolet light, there is such an overwhelming number of these chains that little or no visible damage occurs from exposure to indoor lighting. Visible damage can occur, however, when the emulsion is exposed to  large amounts of direct sunlight outdoors, or when the emulsion has been thinned excessively before application and then exposed to direct sunlight. If a polymer emulsion is applied to a nonoily, absorbent surface, it will remain permanently attached. Although polymer films are quite flexible, there are  situations  where they can crack. Cracking can occur when a polymer emulsion is overloaded with particulate matter, such as additional pigment or sand, or when a  significant amount of polymer is washed out of a paint mixture during the painting process. And an extremely absorbent  painting  ground can draw out enough  polymer from a polymer paint to cause cracking. The color range of polymer paints is limited for two reasons.  The  first con­ cerns pH. Alkaline-sensitive pigments cannot be used in the manufacture of acrylics because acrylic emulsions are alkaline.  Acid-sensitive  pigments  cannot be used in vinyl paints because vinyl emulsions are acidic. The second reason is that in polymer emulsions, subtle differences between similarly colored pigments often cannot be seen and are therefore pointless to manufacture.

 

ACRYLIC POLYMER EMULSION PAINTS

Liquitex, made by the Binney and Smith Company, and Atelier, a lesser-known acrylic paint made by Chroma Acrylics, are examples of the differing formula­ tions of acrylic paints in the marketplace today. Two different formulations  are used for Liquitex, one type for the paint that  comes in  tubes,  and  the other for  the paint that is available in jars. The paint in tubes is designed to have a thicker consistency and to leave brushstrokes the way oil  paint  can.  The  paint  that comes in jars is designed to behave more the way an enamel  paint  would; the  paint film tends to level out and the brushstrokes tend to disappear. Most other manufacturers' jars of acrylic paint are made with the same formulation as their tubes. Thinning tube paints will rarely achieve the same effect as Liquitex that comes in jars, and you usually end up with a thinned paint that still leaves brushstrokes.

Atelier is an example of a new type of acrylic for which updated formulations are used. It is designed to appeal to the impasto painter, who desires texture, thickness, and that heavier oil paint appearance. No matter how a manufacturer decides to formulate the consistency of the colors, additives or media are always supplied to alter the consistency to suit the artist's wishes.

ACRYLIC POLYMER SOLUTION PAINTS

There are certain formulations of acrylic polymer, such as Acryloid B-72 man­ ufactured by Rohm and Haas, that form a solution, rather than a emulsion, in mineral spirits. Magna Color, made by Bocour Company, is  an  example  of  a paint made with this solution as the binder. Its consistency and general working characteristics are like oil paint, but it dries like acrylic. However,  this  type of paint has never attained even half the popularity that  acrylic  emulsion  paints have.

 

VINYL EMULSION PAINTS

Vinyl emulsions are basically the same as acrylic emulsions. The acrylic polymer has one hydrogen atom replaced by a chloride atom, which  results  in  some slightly different handling properties. Paints made from vinyl emulsions dry very matte and evenly. Acrylic emulsion paints tend to dry spottily  with  shiny  and matte areas, even when a medium is added in an attempt to regulate this effect. Painted surfaces  that have variations in surface shine  produce the visual  illusion  of multiple tones of color within one color. This is often a desirable trait for figurative artwork, but is undesirable for most abstract artwork.

It is the matte quality that has made the vinyl emulsion paint Flashe, manufac­tured by the LeFranc & Bourgeois Company, popular among abstract artists. However, vinyl is said to break down more easily than acrylic when exposed to ultraviolet light and is therefore not  recommended  for murals  where  there may  be exposure to direct sunlight.

Vinyl and acrylic paints can, in theory, be mixed together. If they are incom­ patible, the mixture should react immediately, resulting in  a  "cottage  cheese" look, and the mixture will not spread when used. Liquitex colors have,  for example, been successfully mixed when Flashe colors, with the one exception of the Flashe black vinyl paint, which will curdle when mixed with an acrylic.

 

POLYMER EMULSION MEDIUMS

When water is added to a polymer paint  it is not only  thinned  but swollen,  and the color appears thick and rich. When the water evaporates, however, the paint shrinks to a thin, dull, and sometimes opaque appearance. A thicker, more trans­ parent, and deeper final appearance can be achieved by thinning the paint with a polymer medium, or with a mixture of water and polymer medium. As the water evaporates, the medium remains to give some bulk to the paint film. The more medium used, however, the more the pigment particles  are  dispersed  and  the more transparent the paint film.

 

Glazes are best produced by mixing a small amount of color in an undiluted medium. A general-purpose medium for thinning colors is  a  mixture  of  half water to half medium. Whenever polymer paints are to be thinned greatly with water, some medium should be used because if too much of the paint polymer emulsion is washed away or absorbed by the painting surface during the painting process, the paint film can develop cracks.

Both gloss and matte polymer mediums are available to alter the surface reflection to the desired appearance. Matte mediums are produced by the additive silica, or calcium carbonate,  and  tend  to give a milky  appearance  to a paint film if used in large amounts. A gloss medium often doubles  as a gloss  varnish,  but this is not true of a matte medium. A hardener must be added to create a matte varnish that will approximate the durability of a gloss varnish.

 

AUXILIARY PRODUCTS FOR ACRYLIC PAINTING

A number of auxiliary products  are  available for  use in acrylic  painting.  They are designed to prepare a surface for painting, to slow the drying time  of  the paints, or to enable the artist to create texture on a surface.

Polymer Gel is a thickening agent that may be added to a polymer medium. For example, sodium polyacrylate can be added to acrylic polymer emulsions. Gels allow for an impasto style of painting with polymer  paints.  The more gel  used,  the more transparent the paint film. Gels are resistant to cracking and  are excel­ lent as adhesives for collage.

An Acrylic Retarder is either a gel or an additive  that  evaporates  without  a trace. It is designed to slow the drying time of acrylic polymer emulsion  paints. The recommended amount of retarder to be used varies from manufacturer to manufacturer and if specified amounts are exceeded, the paint film will not form properly. Most retarders, when mixed properly with a color, will slow the drying time to approximately three hours. This allows  areas of  a painting  to be blended or reworked in much the same way as can be done with oil paint. 

Acrylic Modeling Paste is a unique product. It is a waterborne, puttylike sub­ stance that dries matte and opaque. It is an acrylic polymer medium mixed with marble dust and titanium dioxide. This product is used to build up  textured  surfaces and sculptured reliefs on absorbent surfaces. If it is to be applied to a flexible surface it must be mixed half and half with gel medium or cracking may result. When this paste is dry it may be carved, sanded, and painted with either waterborne or oil paints. Acrylic polymer paints may be mixed directly into it.

Acrylic Polymer Gesso is not the same as the traditional gesso formulation of white pigment and chalk mixed with hide glue. Although both are designed to create a primed surface for painting, the traditional gesso can only be used on a rigid support, such as a wood panel, since it is not the least bit flexible and will crack if applied to anything that moves or bends. Acrylic polymer gesso is a combination of gypsum, or chalk, titanium dioxide, and just enough  acrylic polymer medium to keep the undiluted mixture from cracking on a flexible sup­ port, such as canvas.

Acrylic polymer gesso can be used to prepare any absorbent surface to receive either polymer emulsion paints or oil paints. Recent investigation seems to indi­ cate that acrylic gesso may be more resistant to chemical  attack  by the pollution  in city air than traditional  gesso for rigid  supports or the traditional  combination of rabbit-skin glue and lead white for canvas supports. Today, acrylic polymer gesso has all but replaced all traditional gessos.

Although acrylic polymer gesso can be applied without thinning, it is much easier to work with if it is thinned. Because  it  has a minimum  of acrylic polymer to provide a very absorbent painting surface, it can crack if  diluted  only  with water and applied to a flexible and highly  absorbent  surface.  It is therefore  wise to add some acrylic polymer medium whenever water is added. Excellent results can be obtained using a mixture of 25 percent  polymer  medium,  25  percent water, and 50 percent acrylic polymer gesso for priming canvas. (For more information about priming and sizing supports).

Artists have reported that some brands of less expensive acrylic gesso may be more subject to cracking. The problem occurs when the gesso is not properly formulated-when it contains too much particulate matter (pigment and filler) in relation to the acrylic emulsion. As the gesso dries, the overloading of pigment prevents the acrylic resin particles from forming a complete paint film, and the resulting paint film is weak and brittle. Problems such as these teach two impor­ tant lessons-read the instructions  on the jar, and combine acrylic polymer gesso  and acrylic polymer paint made only by the same manufacturer.

ACRYLIC VARNISH, GLOSS AND MATTE

Unprotected polymer paint films are not very durable because they are relatively soft compared to oil paint films and can be marred easily as the result of  abra­  sion. They are also more porous and the pigments and  paint film can be affected  by air pollution. A varnish can, however, provide the necessary protection. A varnish can also be used to control the surface appearance in terms of matte and gloss.

Acrylic polymer solution varnishes, which are dissolved in mineral spirits, are the best protection for a_crylic paint films. They are more durable,  forming  a harder protective film than acrylic emulsion varnishes, which are waterborne. Acrylic polymer solution varnishes also provide better protection against air pol­ lutants because they seal the painting's surface more thoroughly. (See Oil Media, Solvents and Varnishes, for more information about synthetic var­nishes.)

An acrylic polymer emulsion varnish is the same as an acrylic polymer emul­ sion used as medium, except that the varnish contains a hardener. Unless spec­  ified by the manufacturer, an acrylic varnish should not be used as a painting medium. Most manufacturers discourage the thinning of acrylic varnishes, and if diluted with more than 50 percent  water, the clarity  of  the dry  varnish  film can be seriously affected

.

The application of a varnish should be smooth and consistent, and areas that might require more varnish should not be reworked. Reapplying a varnish to a partially dry area can result in streaking, evident brush strokes, and a milky appearance. It is best to wait the hour or two until the varnish  dries,  and then apply a second coat. Matte varnishes are particularly susceptible to this problem. The painting surface shine can be regulated not only by choosing a matte or gloss varnish, but also by using a mixture of  the two.  A  matte  varnish, despite the hardeners added to it, is not as durable as a gloss varnish. And the matte surface can be rubbed or polished to a shine.

 

PERMANENCY OF ACRYLIC EMULSION PAINTS

Oil paint  has been  used for several  hundred  years, and  its range of permanency  is well established. Although oil paint is subject to some yellowing and cracking over the centuries, it is still a highly durable medium. Acrylic  polymer  paint, on the other hand, has been in use only for several  decades.  Its range  of  perma­ nency is not established, but is instead implied through accelerated aging tests. Although aging tests have often proven to be quite accurate, they can never take into account all the variables. For example,  acrylic and  vinyl  polymers  seem  to be more vulnerable to weakening from exposure to ultraviolet light (clear acrylic sheeting used in displays and picture framing does yellow in time from the ultra­ violet light in sunlight and fluorescent light) and sulfur air pollutants than previ­ ously thought. This is not to say  that such  paints are  unsafe,  but  rather  that all the data are not yet in and there is still  some  uncertainty  as to  the actual long­ term stability.

As an example of this uncertainty, Binny and Smith rate its most permanent colors in Liquitex, artists' acrylic emulsion paints, as having slight or no color changes after the equivalent of one hundred years of indoor museum exposure. Many of these same colors in oil paint often carry a  rating  that is equivalent  to two hundred or more years before any visible changes occur. Oil  paint  with  ratings of seventy five to one hundred years are often classed only as durable. Again, the point here is not that acrylics will not last as long as oil  paint,  but  rather that no one can yet say, even with accelerated aging tests. 

 

OIL PAINT AND ACRYLIC PAINT

There is a longstanding debate over whether 1t 1s safe to use oil  paint  over acrylics because they are made with different paint vehicles. New research seems  to indicate that these two types of paint film do adhere quite  well  to each other, but only more complete testing will tell if the original  optimism  about the ability of oil paint to bind to acrylic emulsions is  justified. Acrylic  paint,  however, should never be applied over oil paint.

Many people have noticed that oil paint seems to look "richer" than  acrylic  paint. This is partly due to the fact that oil paint vehicles can hold more pigment than can acrylic emulsions. Also, due to cost, most companies that manufacture acrylic paints use less pure grades of pigment when making colors such as cad­mium red and cadmium yellow. (At present, Liquitex's cadmium colors, for example, are made with cadmium-barium pigment instead of pure cadmium. The manufacturer claims that a switch will be made to pure cadmium in the  near future.) One company, Winsor & Newton, is now marketing a line  of  acrylic colors that are made from chemically pure pigments. It  uses  pure  cadmium instead of  the cadmium-barium pigment  that most other companies use.  Whether it makes a great deal of difference if pure pigments are used in acrylic  paints seems to be a matter of personal taste. For instance, different types of  black pigment such as Mars black and ivory black, which are easily distinguished from one another in an oil paint vehicle, look similar when ground into an acrylic emulsion because of differing refractive properties of oil and acrylic media.

  

HAZARDS OF ACRYLIC POLYMER EMULSIONS

The health hazards of  the  pigments used  in acrylic polymer paints are discussed in Pigments, page 227, and Hazards, pages 309 to 323. The  polymer  emulsion itself has hazards of its own that must be considered. Although most major manufacturers have replaced the highly toxic ethylene  glycol  (wet-edge  agent) and toxic preservatives with less hazardous ones  in  their  polymer  emulsions, they cannot be considered safe. Some of the polymers evaporate with the  water and can be inhaled. Although the amounts are not significant in most painting situations, there are many painters who still do stain painting and color field painting, which involve the use of large amounts  of  acrylics,  and  the  artist stands directly over the drying paint without any protection.

There are painters and small manufacturers  making  polymer  paints  who  are not aware of the hazards involved in the  manufacturing  process  and  how  they can be passed along to other users of their paints. For example, the raw acrylic polymer emulsion used in the manufacture of paint contains significant levels of highly toxic and volatile monomers that  must be reduced  or eliminated  for safe use before handling. Not only can the vapors be hazardous, but mural painters should know about the experience of a well-known mural painter who was hos­ pitalized for acrylic and heavy metal poisoning. She was working outdoors on u mural for the Olympics. The heat of the day apparently opened the pores of her skin, allowing a significant amount of acrylic polymer and pigment  to  be absorbed. Although polymer paints are not especially dangerous, they are not as safe as the prevailing opinion, and appropriate precautions are necessary.