It has been more than eight hundred years since the introduction of oil into the technology of painting, and there have been four major factors that have contributed to the development of oil paint and oil painting as they are known today. The first was in 1390 when it was discovered that zinc and lead pigments added to the oil paint sped drying time. This made oil painting feasible in damp or humid climates, such as in Italy and the Netherlands, where oil painting as a viable medium was first introduced.
In the sixteenth century, such natural resins as dammar and mastic were introduced to the oil, allowing for the later development of the thicker alla prima style of painting. This oil-resin paint produced a paint film of great durability and was preferred by many of the Old Masters for use in glazing with successive layers of paint, but most of their specific recipes for making resin-oils and information regarding drying times are now lost. Many artists have since tried to duplicate the technology wherein glazes interlock to give that unsurpassed beauty and clarity so evident in the Masters' work, but, alas, have failed.
The period of industrialization during the nineteenth century brought with it not only a great new spectrum of pigments for artistic use, but also the collapsible tin tube, without which the Impressionist and Luminist painting movements could not have happened.
Pigments such as cobalt blue, chromium oxide green, cadmium yellow, chrome yellow, barium yellow, zinc yellow, cerulean blue, ultramarine blue (synthetic), zinc white, viridian, and cobalt violet were all introduced to oil painting for the first time in the nineteenth century. Such brilliant blues, yellows, and greens had not, and could not have, been seen in painting until this time, but it was the invention of the collapsible tin tube in 1841 that made it practical for the artist to leave the confines of the studio to paint outdoors. Before the development of the tin tube, colors had to be ground fresh or, where available, bought fresh in either perishable animal-skin bladders or expensive metal syringes from colormen, as the first manufacturers of artists' paints were called. The development of prepackaged oil paints was a great advance, though not without some sacrifices in quality, which might seem minor by comparison to the convenience but are nevertheless significant and noteworthy. Resin-oil paints were far more brilliant than resin-free oil paints, and each color could be formulated to dry at a similar rate to allow for proper interlocking of paint films. But, because of packaging and shelf life, resin-oil paint had to give way to resin-free oil paint. Resin-free oil paints have a high oil content with irregular drying times and poorer aging characteristics.
Attempts are still being made to deal with the problems of handling characteristics, packaging, and shelf-life. Some manufacturers are experimenting with different methods of grinding and aging paint and are trying new drying oils or synthetic resins like alkyds, or are even attempting to reconstruct the old resin-oil paint with modern technology.
Oil paint, despite even the advent of acrylic, is still the most versatile, rich looking, and time-tested painting medium of all time.
The Manufacture of Oil Paints
With the Exception, of a few pigments that are too delicate to be made other than by hand, oil paints are generally made by machine. The machine process is far more effective than the techniques used in making paints by hand, and the range of available colors is much greater.
Most commercial artist-grade oil paints are made with some variation, or abbreviation, of the following description supplied by the Holbein Company.
The first stage is the preparation of a mill-base, a mixture of pigment, oil, and resins in ratios prescribed by the natural characteristics of each pigment, which is then placed in an agitator to disperse the ingredients evenly. Some pigments require a vacuum agitator to remove water and gas. If the mill-base is not properly prepared, the next stage of grinding will not be effective.
Additional medium and pigment are mixed with the mill-base and fed into the first series of rollers to grind the mixture and produce a base-paint. The purpose of grinding is to coat each particle of pigment completely with the medium, or vehicle. This isolates and protects the pigment from reacting chemically with other uncoated pigments, and is what gives oil paint its brilliant quality. That quality is determined during this stage of processing. The rollers that grind the paint are made from iron, stone, and ceramic, and are used individually or in combination with varying ratios of revolutions depending on the nature of the pigment (most pigments at this stage are ground three or four times starting with the iron, then the stone, and finally the ceramic rollers to make an artist-grade paint). If there is too much grinding, the pigment will be pulverized and its brilliance lost, and if there is too little grinding, the paint will be oily and gritty.
The third stage is the adjustment process where the base-paint is mixed with an antiseptic, an antifungal agent, driers (if needed), and stabilizers (such as wax, if needed), and is ground two to three times more. At this time, the color is also adjusted to match a previous company standard. The finished product is then tested for tinting strength, covering power, handling properties, resistance to putrefaction, and stability under exposure to light and variations in temperature. After quality control standards have been met, the mixture is aged. This allows any excess oil to separate naturally from the pigment so that it can be removed before the final process of filling the tubes.
The manufacturing process described here is for an extra-fine quality, or artist grade paint. Lesser grades are manufactured with substantially less grinding and quality control, as well as less expensive ingredients.
With the exception of a few delicate pigments such as genuine carmine, madder, and lapis lazuli (genuine ultramarine), the unromantic truth is that handmade oil paint is rarely as good as the best machine-made paint. The main reason is that machine grinding, or ball grinding, coats the individual particles more thoroughly with far less oil (less oil means a lower risk of yellowing and cracking) than could possibly be done by hand. Other drawbacks to hand grinding your own paint are storage problems, spoilage, and considerable health hazards, also assuming you know the proper ratios of vehicle to pigment and how to combine them and that you possess the proper tools. As for saving money by making your own paint, most people who have tried it have found that, for the average painter, it is not worth it.
The only reasons for an artist to make his or her own paint, in spite of all the obstacles, is either for the learning experience or to make a paint that cannot be bought, such as a resin-oil paint or restoration paint; however, even these types of paint are becoming commercially available in the United States.
Blockx paint is the last commercially available, extra-fine, handmade paint. Because it is handmade, it is not only very expensive, but the range of colors is small by comparison to other lines of extra-fine paints and the supply of those colors is extremely limited.
Characteristics of Oil Paint
THE MOST IMPORTANT and unique characteristic of oil paint is the thin coating of oil on each particle of pigment. This coating usually consists of a "drying" oil such as linseed or poppy oil. The oil dries through oxidation, a chemical reaction between the oxygen in the air and the oil, and not through evaporation. This oxidation process creates a remarkably durable and flexible paint film. Since each particle is separated by a clear film, light can pass between some of the particles of pigment, as well reflect off others. It is these characteristics that give this painting medium its great depth and luminosity, when used correctly.
The two most common errors in oil painting are caused by varnishing a painting before complete oxidation bas occurred (a painting may appear dry to the touch in several weeks, but it is often a year before the process is complete enough for a final varnish), and by using too much thinner, which strips off the protective oil coating, often resulting in unpredictable, and sometimes even disastrous effects. Painters will often buy the finest oil paints and then saturate them, using no medium, with the cheapest paint thinner, only to complain about how bad the paint looks and handles.
Without a thorough understanding of the role of drying oils, solvents, varnishes, and pigments, no painter is equipped to take advantage of what oil paints can do.
Over a long period of time, oil paintings will tend to darken, yellow, and develop fine cracks in the surface. Yet the overall beauty and richness has survived centuries. a testament to the durability of oil painting.
PURITY AND LABELING
The term "pure" has been as overemployed in reference to paint as it has in reference to food. It is difficult to derive any practical information from the use of the term. For example, in the making of the finest artist-grade oil paint, only C.P., or chemically pure, cadmium sulfo-selenide (PR 108, C.1. 77196) is used to make a cadmium red color. Yet roughly half the contents of the paint tube consists of oil, with a small percentage of wax stabilizers, and usually a touch of
drier. Consequently, it is difficult to understand what the resulting chemical purity is or means after a pigment has been blended with stabilizers and driers, and in lesser grades of paint, fillers are added, too.
There have been attempts in the recent past to establish some form of standardization in the United States. These efforts have resulted in Commercial Standard CS98-62 , published by the United States Department of Commerce (a copy can be had by writing to the Superintendent of Documents, Washington D. C. , 20025). It is a voluntary standard allowing those who conform to it to say so in their labeling. The standard seems to have been written with a manufacturer's bias, rather than a consumer's bias, as well as a bias toward middle quality, and would seem to eliminate those manufacturers who produce the worst paint and those manufacturers that produce some of the best paint (primarily in the area of resin-oil) from using the approved label. Few manufacturers ever fully comply with this standard.
Another important outgrowth of the standardization efforts is the use of color indexing for artists' paints. Color indexing is a fairly specific method of identifying a pigment and establishing purity. (For information about this seven-volume index, write to the American Association of Textile Chemists and Colorists, P. O. Box 12215, Research Triangle Park, NC 27709. A reference copy can often be found in a university chemistry library or a public library that has a science reference section.) This information is particularly important to restorers, decorators, and paint manufacturers. The indexing numbers can be helpful to artists when these numbers are accompanied by the traditional names and chemical names for the pigments and, in cases where more than one pigment is used, their ratios. At this time, no manufacturer is supplying such ratios when more than one pigment is used. Some have even eliminated the traditional name in favor of only the index number, which is most discouraging because it makes valuable information inaccessible to all but the most scientific of painters.
A set of voluntary standards is now being established by the American Society for Testing and Materials (ASTM). This will be an improvement on the Commercial Standard CS98-62 , as well as on labeling. Voluntary standards concerning health hazards and the labeling of hazardous materials are set down in ASTM D 4236, Standard Practice for Art Materials for Chronic Health Hazards. ASTM D 4302, Standard Specifications for Artists' Oil and Acrylic Emulsion Paints, deals with improved labeling, while ASTM D 4303, Test Methods for Relative Lightfastness of Pigments Used in Artists' Paints, attempts to standardize lightfastness test procedures. A copy of each of these documents is available, for $8.00 each, from ASTM Sales Services Dept., 1916 Race Street, Philadelphia, PA 19103. Manufacturers that conform to these standards will be permitted to say that their product "Conforms to ASTM D 4302." The ASTM recommends guidelines for proper testing and labeling, but does no testing. The supplying of accurate and meaningful labeling, as well as supplemental product information, is still almost entirely up to the good will of the manufacturers of artists' materials. Compliance with these guidelines should be higher than it has been with Commercial Standard CS98-62.
Winsor & Newton makes a point of advertising the compliance of its London Oil Colour and London Alkyd Colour with these new standards. (These two lines of Winsor & Newton paint are, however, its lesser grade; it has, curiously, not involved its artist-grade oils.) It boldly labels its compliance on these paint tubes. But this information is no more meaningful to the average consumer of artists' materials than was the Commercial Standard CS98-62. The company has added such information as the chemical name of the pigment used, a permanency rating, a lightfastness rating, and the vehicle used. At first glance this would appear to be a vast improvement, yet most of this information has been commonly supplied on paint labels by most manufacturers for several years. The remaining information, as with virtually all current labeling, is in a form that, recurrently, is not truly meaningful.
Complete labeling, backed up with easily accessible, in-depth technical information, is needed. The labeling on artists' paints should be at least as good as what we have now come to expect on the food we buy. This is easier said than done, especially in an industry with such a variety of products. It is obvious that new labeling is continually developing, and it would be a great service to the artist if labels supplied meaningful information. The subject of purity and standards is already controversial, but it is nevertheless necessary to point out how little practical information, especially in regard to purity, is accessible to the average painter, who is often left with little alternative but to accept the reputation of the manufacturer.
Permanence, in regard to the lightfastness and compatibility of the pigments, is discussed extensively in the chapter on pigments. It is important to understand, however, that the general permanence of colors in oil paint is dependent on the protective coating that each particle of pigment possesses. Although the protective coating allows the use of many pigments that might otherwise interact chemically if combined in their dry unprotected form, it also reduces the permanency of the color that is produced by the pigment. As the protective coating ages, it tends to darken and yellow, particularly if that coating is comprised primarily of linseed oil, which changes the color.
The permanence of oil paint is also affected by atmospheric pollution, such as the sulfur dioxide and hydrogen sulfide present in city air. Unprotected (unvarnished) metal-based paints like the chrome colors, such as chrome yellow, and chrome green, white lead, cremnitz white, cinnabar green, as well as colors like ultramarine blue and permanent blue, can discolor when they come in contact with these pollutants.
Such colors as alizarin crimson, brown madder alizarin, indigo, permanent green, and purple madder alizarin are not as permanent when used in thin glazes. Scarlet lake (BON arylamide) and Winsor orange (BON arylamide and arylamide yellow) oil colors by Winsor & Newton are particularly sensitive to pale tints with white. Mixing white, or any color of greater pem1anency, with colors of lesser permanency does not improve the permanency of the latter and often reduces it.
The ability of an oil color to maintain its strength when mixed with white is known as tinting strength. This is a common test for pigment concentration and a valid method of comparison between brands of paint if the pigment used by each is the same. The name of the color on the tube does not necessarily indi cate what is in the tube. For example, a well-advertised tinting test shows two different brands of raw sienna. The advertiser's brand show greater strength of color. However, the pigments tested are similar, but not the same. The weaker appearing brand of raw sienna is said to contain iron oxide mined from the traditional sites in Italy, which is high in silica and produces a more transparent color. The advertiser's brand is said to be a manufactured iron oxide, which contains no silica and thereby produces a stronger tinting strength. The point is not which is the more desirable characteristic and thereby which is the better paint, but rather that this is not a fair comparison.
Tinting tests can be made fair and can be performed by anyone once two identical pigments from two different brands have been identified. Within two brands of paint, about 25 percent will cross match using the same single pigment for a particular color. It is important to avoid testing colors that contain several pigments, even if they are identical, because the proportions for each pigment may be different. You can make a test mixing half zinc white with half color, and then take half of that mixture and mix it with half zinc white again, and repeat this procedure several times for each brand. This will give you a serial dilution, which can then be compared.
Small differences between brands in tinting strength are best ignored because the most concentrated use of a pigment to make a color is not always desirable. Some pigments become literally unworkable above certain concentrations. Paints made with too high a concentration of metal pigments such as cadmium or lead become so thick and cakey that they cannot be easily expelled from the tube or manipulated on the palette. Paints made with some of the newer synthetic pigments, such as phthalocyanine, have such high tinting strength that if they were used in high concentrations, they would totally overpower any color mixed with them. Because of these factors, manufacturers balance the level of concentration with the working consistency. Any home-done tint test comparison needs to be judged against your preferences for the particular paint consistency that a manufacturer offers.
TRANSPARENCY OR OPACITY
In oil paint each pigment, by its own chemical nature, will tend to be either transparent, semitransparent, or opaque. Most blacks, blues, violets, and purples are transparent, as are colors where the pigment is a like a dye-pigment, such as alizarin crimson and madder. Earth colors range from semitransparent to opaque, depending on their source. All cadmium and chrome colors, all whites, or colors that are made with white (such as Naples yellow and flesh tint), and genuine vermilion are opaque.
Of all the whites, zinc white is most transparent, followed by lead white and then titanium white, the most opaque. You can make a transparent color semi transparent or opaque by the addition of white. Many colors will take up to 10 percent white without any appreciable change in the surface appearance. Opaque colors can often be made semitransparent by thinning them with a painting medium and applying in thin glazes.
Virtually all manufacturers' color charts are encoded with information regard ing the transparency and opacity of the colors in their unmixed state. Some companies, such as Schmincke, even label their paint tubes. It is important to note that in lesser grades of paint, it is more common to have expensive colors replaced with blends of other less costly colors, which in turn can affect the transparency and opacity. A mixture of white and phthalocyanine blue, for example, is sometimes sold as cobalt blue, or cobalt blue hue. This blend is opaque and does not produce the same kinds of tints when mixed with other colors. Genuine cobalt blue is prized for its transparency as well the delicate tints it can produce. Another example is cadmium red, the better grades of which are made from C.P. cadmium sulfo-selenide, and which is prized for its opacity and brilliance. It is sometimes replaced with lesser grades, which are often mixed with barium sulfate, and are therefore less opaque and not as brilliant.
It used to be common practice simply to paint over undesirable areas with opaque colors until it was discovered, after many years of aging, that areas which were hidden began to show through the increasingly transparent surface. This phenomenon is called pentimento. Therefore, if an area needs to be repainted, the area should first be prepared with a new ground of white paint. To an artist who paints very large, these differences may seem insignificant for, if one has to stand twenty to thirty feet back from the surface of the painting to see it, it is unlikely that small details will be noticed. However, if you are a master at the craft of painting, or paint in a style where details must and will be seen, these differences are very important.
The nature of oil paint is such that particles of pigment are coated and suspended in a liquid, which, in turn, will bind those particles together when exposed to air. That liquid may be a drying oil, a resin-oil blend, or an oil-modified alkyd resin.
Drying Oils. These oils are used in grinding pigment to form an oil paint, as well as to make media for oil painting. It is the linolenic and linoleic acids present in a drying oil (commonly linseed oil) that, when in contact with air, oxidize to form a film that binds the particles of pigments together.
Some manufacturers substitute a refined poppy oil or safflower oil for linseed oil in preparing certain pale oil colors and whites. These drying oils have little or no linolenic acid, a binder that gives a yellow tint to oil paint. The only binder in these oils is the linoleic acid, which is not only less yellow, but also yellows less over time. However, linoleic acid by itself is a weaker binder and should not be used as a replacement for linseed oil in all cases.
Using a "pure oil" system of making paint is the least costly method and, unless driers and wax stabilizers are added to certain colors, there will be wide variations in consistency and drying times between many colors. This type of paint is referred to as "fat" paint because of the high oil content. The fatter the paint, the more yellowing and the greater the possibility for future cracking. Some manufacturers have attempted to reduce the "fat" either by an elaborate grinding system, such as that used by the Holbein Company, or by aging the
paint before packaging, a method employed by Grumbacher
Resin-Oil. The Schmincke Company has developed the use of a resin-oil binder, which is stable in tube paints and similar to that used by the Old Masters. Its line of oil paint has been named Mussini in honor of Cesare Mussini, a nine teenth-century painter and teacher who was one of the few remaining repositories of some of the Old Masters' paint-making recipes, and who passed this knowledge on to the colormen of Schmincke. Mussini oil paint is made with such drying oils as cold-pressed and refined linseed oils, poppy oil, and sunflower oil, which are blended with natural resins like dammar and mastic, as well as with polycyclohexanone, a modem nonyellowing dammar-like resin.
This elaborate formulation allows for four important effects: more even drying of paint films, which reduces the possibilities of future cracking; greater clarity and less yellowing because of the lower oil content; narrowing the range of drying times between different pigments; and smooth and even consistency with little or no separation of oil and pigments.
The mixing of such ingredients as mastic and dammar into a paint after it has been ground with only linseed oil, will help to improve the paint's performance. However, it is not the same as when the pigment is ground into the same com bination of ingredients to start with, where less oil and more resin can be used. When the ingredients are added later to a high-oil-content paint, the original oil in the tube is only diluted, not replaced, and the increase in performance is not as dramatic.
Oil-Modified Alkyd Resin. Alkyd resin is the category of resins that are made from mixtures of dibasic acids and polyhydric alcohols. One particular alkyd resin (kept a trade secret) is chemically combined with a nonyellowing oil, such as safflower oil, to produce a workable, fast-drying binder for oil paints. Driers are often included to speed drying and silica is occasionally added to give extra body.
Alkyd resins often exhibit a thixotropic effect. Thixotropy is an unusual phenomenon in which a gel, or paste, suddenly loses its plasticity when disturbed or moved mechanically, resulting in a liquid. The opposite may also occur where a liquid, left undisturbed, forms into a gel. There is a certain advantage to this thixotropic property in the glazing technique, for a glaze will resist running down the canvas after it has been applied and left undisturbed. However, the tendency of alkyds to liquify rapidly would be a disadvantage in the impasto technique.
Alkyd resins, originally developed for use in making industrial paints, have been applied to make a variety of fast-drying media for artists' paints. Winsor & Newton has produced two lines of paint (an artist-grade and an amateur-grade) where the pigments have been ground into an oil-modified alkyd resin. The range of colors is limited to its "selected list" (SL), which consists of colors that may be mixed with one another without loss of permanence. At this time it is not clear if pigments other than those currently used in nonalkyd paint are safe to be stored in tubes after being ground into this acidic resin. It does seem to be all right, however, to intermix nonalkyd paint with alkyd paint, and nonalkyd medium with alkyd medium for immediate use.
Alkyd paints and alkyd media should not be overthinned. No more than 25 percent by volume of thinner to paint or medium is recommended; more than this will break down the consistency and quality of the paint or medium.
Each pigment affects the drying rate of its oil vehicle differently. Some speed the oxidation process, some slow it down, and some have no effect at all. To compensate for this, most manufacturers add a small amount of drier, such as cobalt or manganese, to the slowest-drying colors. This narrows the range of drying times within a line of paint, but, even with these driers, some colors' drying times may differ from others by several days to several weeks.
Natural and synthetic resins are also used to narrow the range of drying times further. Winsor & Newton has accomplished this in its alkyd paints by using an oil-modified alkyd in which it grinds its pigments. The Schmincke Company has narrowed the range of drying times by using a resin-oil formulation specific for each pigment in its Mussini paint. However, these two paints are unique. Most other brands of oil paint have a large gap in drying time between certain colors and caution in their combined use may be necessary.
In general, a faster-drying paint should never be applied over a slower-drying paint; otherwise cracking may result. Some of the slowest-drying colors not recommended for underpainting are all carbon-based blacks (ivory, lamp, carbon, and charcoal black), all cadmium-based paints (cadmium red, cadmium yellow, cadmium green), vermilion, alizarin crimson, zinc white, and Vandyke brown. These colors, unless modified by the artist or the manufacturer, can take between three and five days in a thin paint film to dry.
Among the faster-drying colors are the cobalt-based colors (such as cobalt yellow, cobalt blue, and aureolin), manganese-based colors (manganese blue, manganese violet, and manganese black), raw and burnt umber (both contain large amounts of manganese), Prussian blue, and lead-based whites and colors (including flake white, Cremnitz white, Naples yellow, chrome red, and chrome yellow). Some colors, such as the manganese-based colors, have a strong catalytic effect upon drying oils and are often ground into poppy oil in order to slow the drying time.
Each manufacturer does or does not adjust the drying rates of its colors according to its own idiosyncrasies, and most do not supply information about the drying times or the film characteristic of their colors. Because of the variations, generalization will often not be discovered until after use. An understanding of the nature of pigments, combined with knowledge of the pigments used by a manufacturer to produce a particular color, will help you to infer a drying rate. In addition to modifying drying times through the use of media, a painter can accomplish the same goal by mixing slow-drying colors with fast-drying colors.
In addition to varying drying times among pigments, there are also varying film characteristics, which can range from tough and flexible to hard and brittle. It is the brittle film characteristics that are of greatest concern, particularly when used in underpainting. If a brittle paint is used underneath, it may cause the over painting to crack.
Zinc-based paints, such as zinc white, are the most brittle and are not recommended for use in underpainting. Cobalt-based colors, barium yellow, strontium yellow, and red oxides, although not as brittle as zinc paints, are also not recommended for use in underpainting. Lead-based paints, raw umber, and burnt umber are among the most flexible paints and are perfect not only for under painting, but also for mixing with more brittle paints to stabilize them.
Ideally, little or no stabilizer should be used in an artist-grade paint. There are certain pigments, when ground into linseed or poppy oil, that could either have a stringy consistency or a tendency to separate from the oil. Such stabilizers as waxes (beeswax or aluminum stearate), water, and alumina hydrate (added to give bulk) are currently utilized to regulate consistency. Although there are definitely cases where it is more helpful than harmful to have these additives, the use of these materials has been abused. Consistency is often mistaken for quality, and it is certainly more profitable for a manufacturer to use stabilizers rather than pigment to meet the artist's expectations
Stabilizers easily cross over into use as fillers. It is considered acceptable by most manufacturers to use, for example, as much as I to 2 percent aluminum stearate, by weight, to improve the consistency of some colors. However, aluminum stearate weighs very little compared to the volume it can occupy. Aluminum stearate does to oil paint what goose down does to a comforter; it is easily possible for this wax to take two to four times its weight in volume. If an "average" tube oil paint consists of 50 percent oil to 50 percent pigment by volume, the adding of 2 percent aluminum stearate, by weight, could reduce the amount of pigment by volume by 8 percent to 42 percent. Although certainly significant, this is not serious. It becomes serious when more than 2 percent by weight is used, not only because it replaces more pigment, but because it becomes necessary to increase the proportion of oil to offset the increased effects of the aluminum stearate. If 5 percent aluminum stearate, by weight, is used, it is quite possible to end up with volumes of 70 percent oil, 20 percent aluminum stearate, and only 10 percent pigment.
It is rare to see this kind of abuse in artist-grade paints because most of the cost of making these paints is for labor and not for materials. Most manufacturers of such paints find it pointless to scrimp on raw materials. In lesser grades, however, where competitive pricing is so important, the quantity and quality of labor and raw materials are reduced and one of the most effective ways to accomplish both is to increase the use of a stabilizer like aluminum stearate. The artist can sometimes detect the excessive use of stabilizers by doing a tinting strength test.
OIL SEPARATION FROM PIGMENT
The separation of oil and pigment in an artist-grade paint does not necessarily indicate poor quality; it often means that little or no stabilizer was used. How ever, it can also indicate the lack of aging, lack of resin (natural or synthetic), or lack of modem grinding techniques, none of which would necessarily be serious drawbacks.
Separation commonly occurs in pigments containing cobalt, manganese, cadmium, and lead and appears to be due to an aging process whereby the surface tension of certain pigments is reduced with age, which results in a lesser amount of oil being needed to coat a particle. The excess oil is naturally expressed and causes the .apparent separation. It is not uncommon to find an "old time" painter looking for old tubes of paint, rather than "fresh" tubes, because the aging process improves the quality of oil paint (as long as the container is closed). Some of the finer quality paints are aged up to six months to allow this separation to occur before packaging.
The separation of oil and pigment in lesser quality oil paints often indicates that too much oil was used in the manufacture. This would be especially true of paints in which stabilizers are commonly used to compensate for excessive oil.
DIFFERENT GRADES OF PAINTS
Three grades of paint seem to have developed in the United States: artist (finest, extra-fine, super-fine), amateur (fine, professional), and student. The European products that are available in the United States are often of two grades: artist and student. Many of the European student-grade paints are equivalent in quality to American amateur-grade paint.
In general, artist-grade paints are supposed to be made with only the purest, highest-quality ingredients, without regard to cost. The paint is manufactured according to the tradition that each company has established for itself and upon which it rests its reputation. Amateur-grade paints are made from the best ingredients that can be found at a reasonable price. The level of craftsmanship, although not as fine as in artist-grade paint, is sufficient to produce a consistently good-quality paint that is still safe for professional use. Student-grade paint made in the United States is designed to be used for studies or learning exercises that will most likely be discarded. Therefore, this paint is made with the least costly raw materials and with the most cost-effective methods. Within each of these grades there are also varying levels of quality.
To complicate matters, some companies have recently begun to call their amateur grade "Professional," a term that seems to imply some equivalence with artist-grade paint. The best way to avoid being confused by all this is to learn about the pigments that are used to make paint. For example, the finest cadmium red paint is made only from the purest cadmium sulfo-selenide (PR 108, C.I. 77196), and not from such cadmium-barium sulfo-selenide mixtures as PR 108, C.I. 77202, which contains less than 15 percent barium sulfate, or PR 108:1, C.I. 77202, which contains more than 15 percent barium sulfate. Such cadmium barium mixtures fit into the amateur grade because they tend to be weaker in intensity and the paint is more transparent depending on the amount of barium sulfate filler. Cadmium red hue, which is mostly found in student-grade, and occasionally in amateur-grade, paints is made with azo red pigments. It is a less expensive alternative to the cadmium pigments, but has a slightly unnatural appearance and, when mixed with azo yellow pigments, produces a dull orange. When you have this information, you can make an educated choice. You may even choose the azo-pigmented color over the cadmium-barium color for a esthetic reasons. Price may be a factor in making your decision as well, because the finest cadmium red paint is expensive. If you paint large pictures, which have to be viewed twenty to thirty feet away, the difference in the quality of the paint you select may not be seen.
In amateur and student grades of paint, the hue of expensive pigments may be imitated by using mixtures of less costly pigments. Cobalt blue, for example, is often simulated using mixtures of phthalocyanine blue and white. This kind of mixture looks similar in surface hue to the actual pigment, but it is opaque and duller than genuine cobalt blue. When mixed with other colors, the imitation tends to muddy the appearance.
Student-grade paints are not, and should not be, used for professional work. Making a choice between amateur-grade and artist-grade can simply be based on whether you can or cannot see the difference. The difference in quality is most obvious in such colors as manganese blue, cobalt violet, cadmium red, and Van dyke brown. A comparison of one or more of these colors can be made by spreading some of each color on a sheet of glass with your fingertips. (Wash your hands thoroughly afterward.) If you cannot see, feel, or care about the difference, then it is pointless to buy the more expensive paint.
LARGE TUBES AND CANS OF OIL PAINTS
The renewal of interest in oil painting, particularly large oil paintings, has fostered interest in larger and more economical volumes of paint. A few companies have offered larger volumes of paint for some time. LeFranc & Bourgeois, for example, markets 250 ml tubes of the more popular colors of its 104 series (its second-grade, or amateur-grade, paint). In the past few years, small manufacturers have begun to produce cans or jars of oil paint. Recently, larger manufacturers, including Grumbacher, Martin/Weber, Maimeri, and Winsor & Newton, have entered this market, too.
The range in quality from brand to brand is great, and the lure of large volumes and low prices has led many artists to buy paints for expediency without checking the label or comparing quality. Most major oil paint manufacturers produce several grades of paint to cover the potential marketplace. At this time, no company is packaging its finest paints in large volume because even with the savings such paints in large quantities would still not be affordable for the aver age artist. What is being offered is either a second grade, also called professional grade, or the manufacturer's student grade. In some cases. a new. even lower quality than student grade is made to fill these large tubes.
These new large tubes, jars, and cans have to be looked at and tested carefully. Some of these paints are labeled Cadmium Red (Hue) when actually three separate pigments are used to make a simulated color, none of them cadmium and one of them white. Even if you ignore the potential permanency of tertiary colors such as these, the mixing properties would be absurd. I particularly recommend that any paint that is a student grade or less should not be used professionally. Student-grade paints are for exercises and experiments where the final work is not sold. There is good quality, large-volume paint available at a substantial savings, but you must become an educated consumer to find it.
MIXING BRANDS AND GRADES
There are no precautions necessary when mixing different brands or levels of the same quality of oil paint. However, mixing an artist-grade paint with a student grade paint does not give birth to an amateur-grade paint. In fact, few painters mix levels of quality. It is most common to underpaint with an amateur-grade paint and save the more expensive, better-quality, artist-grade paint for the final stages. This is a safe method of economizing.
The mixing of different brands of paint within the same level of quality, although perfectly safe, is not as common as might be imagined. Most painters develop a brand loyalty, and behave as if they were cheating on a lover when an interesting or unusual color is found in another brand. To put such attitudes in perspective it would be helpful to understand that although there are definite distinctions among brands, such distinctions are not so great that they should inhibit selections.
In an artist-grade paint it is not uncommon to find as many as a hundred and fifty different colors. Approximately one-third of the colors is made using individual pigments in their natural state. Another one-third of the colors is the same pigments chemically or mechanically (grinding) modified to change the color. The remaining one-third is colors produced through mixing two or more pigments together. In lesser grades of oil paint, the color range often consists of only thirty-five to fifty colors, which rely heavily on mixtures of pigments to obtain much of the range.
It is a common misunderstanding among inexperienced painters that most of these colors can be duplicated with the use of a "good red, yellow, and blue." Although the final one-third of a color line can often be duplicated easily with a palette of colors consisting of one warm and one cool of each of blue, red,· yellow, and violet with some additional help of white and black, the qualities of the other colors cannot be duplicated by mixing. Surface color, or hue, can often be made similar to the other two-thirds of a color line, but depth and brilliance cannot. Secondary (two colors mixed) and tertiary (three colors mixed) colors do not function well as tinting colors, often muddying the appearance of other colors. One example of this is cobalt blue hue, manufactured by some paint companies to simulate the more expensive cobalt blue. While the hue resembles the real thing in surface appearance, it is duller and is opaque, not transparent.
Experienced painters usually try to buy a needed color rather than mix it, and they try to use it in its purest form whenever possible. Consequently, large color lines exist primarily because of the demands of the painter rather than because the manufacturers are looking for something else to sell.
In most painting techniques one-half the amount of paint used is white. The type of white, or the combination of whites, used plays a large role in determining the appearance of a work. There are three basic kinds of white-lead, zinc, and titanium.
Flake White is lead carbonate that has been ground into poppy or safflower oil (to slow the drying time and reduce yellowing) and to which a small amount of zinc is often added to improve consistency. Flake white has the greatest durability and is the most flexible of all the whites. It is not as white as zinc white nor as opaque as titanium, but is excellent for making tints of cooler colors, and can safely be used in underpainting. It is poisonous if ingested or if the powdered form is inhaled, but not through skin contact. Flake white can blacken if it is left unprotected against hydrogen sulfide, an atmospheric pollutant, so varnishing is a must.
Cremnitz White is the same as flake white but without the zinc additive. Its consistency is a bit drier and stiffer, and it is preferred by purists. Cremnitz white and flake white used to be known for yellowing because of linseed oil, but linseed oil is rare!y used in making this paint today.
Foundation White, which is produced by a few manufacturers, is also lead carbonate, but this is ground into linseed rather than poppy or safflower oil. The paint films formed by poppy and safflower oils are not as strong or flexible as the film formed by linseed oil, and would not be as safe to use as a painting ground. Foundation white is specifically designed as a painting ground.
Zinc White, which was originally developed as a nonpoisonous alternative to lead carbonate, is effective but not as versatile. Zinc white is zinc oxide ground into poppy or safflower oil. It is the least opaque of all the whites and is ideal for tinting and glazing. It is not darkened by hydrogen sulfide. The major draw back of zinc white is its brittleness and, because of this, it cannot be used as a ground or in underpainting.
Titanium White is titanium dioxide ground into poppy or safflower oil (some times a portion of linseed oil is used). It is the most opaque and the whitest of the whites and, in its pure state, it can reflect more than 97 percent of all light. It is also the newest and now the most popular of all whites. The permanency rating is among the highest given to a pigment.
Blends of Whites are produced by several manufacturers. The most popular is a blend of zinc and titanium. Permalba white, produced by the Weber Company, is among the most popular of the available blends.
OIL PAINTS VERSUS OTHER PAINTING MEDIA
It is easier to learn how to paint with oils than with most other media. At the same time, it is the most difficult of media to master, primarily because it is so versatile. There are so many styles of painting, formulas for media, pigments, and tools in oil painting that many find they do not have the patience necessary to master this medium. There are many quicker, less complicated media of expression, but, with the exception of egg tempera, none is as rich or as time tested as oils.
Oils are most often compared with acrylics. Although acrylics were developed for artist use only forty years ago, this medium has taken over a large share of the artists' materials market. Many painters have begun in, or switched to, acrylic because of the lower costs, availability in larger volumes, fast drying, easy clean-up, absence of hazardous thinners, and nonyellowing characteristics. Nevertheless, I have yet to hear anyone say that he or she uses acrylics rather than oils because they look better. In general, acrylics are primarily used as an alternative to oil.
The nature of acrylics prevents them from being as concentrated with pigments as oil paints, or as brilliant in appearance. Some pigments traditionally used in oil paint are not used in acrylics because their unique qualities cannot be seen in a polymer medium. The available color range of acrylics is narrower because many pigments cannot survive the alkalinity or cannot stay in suspension. Acrylics have only a narrow range of available media, and are therefore less versatile. They also dry with a much darker appearance than the wet color, which can be deceiving for the beginner. If acrylics were compared to the classification of grade levels used for oils, they would fit the amateur grade.
The only other medium that has often been compared with oil painting is egg tempera. When used properly, it can be more brilliant, luminous, nonyellowing, and permanent than oils. However, the techniques for egg tempera are even more difficult to master, and it is a more fragile medium.
OIL PAINTS AND OTHER PAINTING MEDIA
Although water-based paints, such as acrylics and vinyls, should not be painted over any oil-based paint, oil-based paints can safely be painted over water-based polymer emulsion paints. This has been verified by manufacturers of both types of paint. Because of reasons involving economy and drying time, it has become common to underpaint with acrylic and finish with oil paint.
The use of wax in encaustic painting is a long-established, safe painting method. However, there have been some problems in the use of encaustic paints and oil paints within the same painting. Paintings in which oil paint has been applied over areas consisting of high proportions of wax have cracked and some times the paint has fallen off the surface. Wax appears to dry quickly, but, in reality, it only sets up quickly, for it takes years to cure, certainly far longer than the oil paint applied over it. This would violate the rule of never applying a faster-drying paint over a slower-drying paint.
The use of encaustic should not be a start-and-stop operation. Once wax is used, it is safer to finish with wax and not with oil.
The mixing of such drawing materials as pastels, paint sticks, and crayons with oil painting has become popular. Materials such as these should be reserved for the final stages of a painting. Oil pastels, crayons, and paint sticks are made of wax and pigment and should be treated as an encaustic paint. There is one paint stick made by Edding Company that is an acrylic, lacquer-based paint stick that behaves more like a paint than a wax. This quality would make it safer to use in underpainting. Soft pastels are more difficult to use safely because of their chalky nature, which can give unpredictable results. However, charcoal has traditionally been used for preliminary, light sketching on the canvas before the painting is started, and can be used safely in moderation if the charcoal is fixed before the application of oil paint.
Although the use of mixed media can be a powerful method of expression, many an art conservator has had to repair works in which materials were thrown together carelessIy.
THE ROLE OF MEDIA IN OIL PAINTING
A medium is a recipe that includes, in specific proportions, two or more of: drying oil(s), resin(s), drier(s), wax(es), and thinner(s). A medium, in addition to regulating the consistency of the paint, thinning or thickening it, will also regulate the drying time, transparency, gloss, and leveling characteristics, as well as improve the overall aesthetic appearance.
If you are glazing without a thickener, such as Venice turpentine, for example, the thinned paint will simply run down the canvas. If the various drying times between differing pigments are a problem, this can often be resolved with the use of a medium formulated to narrow the drying time. Sometimes the impressions left by brushstrokes are undesirable, and can be made to disappear by substituting stand oil for refined linseed oil. Depth, brilliance, and subtlety are all controlled by such resins as dammar, mastic, and venice turpentine. More than one medium may be used in the course of a painting's development, and each would be used at different stages.
Oil painting without media, or with only linseed oil and turpentine, is like placing an order at a French restaurant for boiled duck, no sauce, no salt, and no butter. An appropriate medium does for oils what a French chef does to an otherwise bland and greasy dead bird, and the results, like Duck a' lOrange, are exquisite.
Although hazards are discussed in depth in the chapter on hazards, it is important to stress here that the primary danger in working with oil paints lies with the use of thinners and the seemingly miraculous ways that painters seem to ingest and inhale paint without "eating" it.
Turpentine, until recently, had been thought to be one of the safer thinners that an artist could use, but now it has been rediscovered that turpentine can enter the body not only by inhalation, but through the skin. I say rediscovered because during the nineteenth century turpentine was used as liniment to carry herb and other remedies into and through the skin. Today, it seems to be a big surprise to everyone in the artists' materials trade that turpentine can pass through the skin. There have been reports of kidney damage and changes in the bone marrow in a very small percentage of painters who were said to be using this thinner as any average painter would. Even worse is the physical damage to painters who use industrial thinners, which often contain far more hazardous chemicals.
It has been common to see painters having lunch, smoking, and biting their nails, with paint on their hands, in the folds of their skin, and caught under their nails. There are also artists who airbrush in their living space or in their studio without adequate ventilation, protective clothing, or breathing apparatus. An all too-common response to the hazards of oil paints, from many of these same individuals, is "I'm not stupid, I don't eat my paints!"
Common sense, good work habits, and some basic knowledge about the hazards concerning the materials you use could save your life or, at least, the quality of your life.
Techologcal and chemical advances over the past few centuries have enabled the manufacture of an increasing variety of colors in oil paints. The following lists give some indication of how the spectrum of colors has expanded, and also suggest a basic selection for the contemporary artist.
COLORS AVAILABLE DURING REMBRANDT'S LIFETIME
Red Lead (replaced by Cadmium Red) Madder
Umber (although available, it was more often mixed) Sienna.
Realgar (an arsenic orange, not used since the Renaissance)
Orpiment (an arsenic yellow, not used since the Renaissance)
Malachite Green (fell into disuse after the eighteenth century) Ultramarine
Azurite (replaced by Cobalt Blue in the eighteenth century) Indigo
Ivory Black Lead White
COLORS AVAILABLE TO THE IMPRESSIONISTS
Alizarin Crimson Zinc Yellow Emerald Green Vermilion Aureolin (Cobalt Yellow)
Chrome Red Sienna, Burnt and Raw Artificial Ultramarine Madder and Rose Madder
Umber, Burnt and Raw Cobalt Blue Indian Red Vandyck Brown Cerulean Cadmium Yellow
Prussian Blue (pale, middle, and deep) Malachite Green Cobalt Violet Chrome Yellow
Yellow Ochre Permanent Green Deep Lead White Viridian Ivory Black
Naples Yellow Chromium Oxide Green Zinc White Chrome Green Green Earth
Barium Yellow Cobalt Green
A SUGGESTED CONTEMPORARY PALETTE
Lemon Yellow Cobalt Blue Indian Red Cadmium Red Light
Ultramarine Blue Burnt Sienna Burnt Umber
Cadmium Yellow Phthalocyanine Blue Cadmium Yellow Light
Alizarin Crimson Phthalocyanine Green Mars Black
Chromium Oxide Green Lead White Viridian Ivory Black Cadmium Red
Cobalt Violet Yellow Ochre Titanium White
A SUGGESTED BEGINNER'S, OR ABBREVIATED, PALETTE
Viridian Yellow Ochre Burnt Sienna Burnt Umber Ivory Black