Guidelines Concerning Art on Canvas or Panels

(Excerpt from ART HARDWARE: The Definitive Guide to  Artists’ Materials, by Steven Saitzyk © 1987)

Artwork done with oil paint or acrylic is  usually painted on a support of stretched or mounted canvas. In a small  percentage of cases it is painted on wood or metal panels. This type of artwork,  if properly varnished, does not have to be framed with glass because the surface  is more easily cleaned and is less subject to permanent damage from mechanical  disturbances. Nevertheless, a cer­tain amount of additional protection is  needed, which can be supplied by the edge of the moulding used to make the  picture frame. The moulding covers the edge of the painting and protrudes above  the surface of the painting. This helps to protect against the most common form  of mechanical abuses and problems in handling.

Paper artwork, from the outset of its  development, was framed for protection first and for decoration second. This is  not true in the case of early frescoes and paintings done on panels. The  earliest picture frames were made to create a focal point or atmosphere in which  the artwork could be seen. The oldest known frames were doorways or archways  that served as a focal point through which to view a scene or to outline some  architecture, as well as serving as an entrance or exit. Today, a carpenter’s  term for the process of installing a door is still “fram­ing a door.” It was not  until the late seventeenth century, when painting had developed the technology  to be portable, that the notion of protection came to be a major consideration.  The following rules apply to art on canvas and panels with oil paints or  acrylics.

1.                Never attempt a perfect fit;  you must leave sufficient breathing space for expansion and contraction of the  artwork and the materials used in framing it. The standard allowance for paper art with glass  is 1/16 inch and for stretched art it is 1/8 inch if possible. Some commercial  mouldings, because of the width of the “rabbet” (the lip of the moulding into  which the artwork is installed), do not allow for 1/8 inch and you may have to  settle for 3/32 inch to prevent the edge of the picture from showing. The larger  allowance is recommended because stretched artwork is not sealed from  atmospheric conditions and is more subject to variations in temperature and  humidity. In addition, the wood or metal used as a support for the painting is  rarely the same as that used for the frame. Consequently, each will expand and  contract differently and will need the allow­ance so that one does not restrict  the other and lead to warping and damage.

               Cross Section of Framing a Stretched Painting





2.               Never nail, toe nail, staple,  or screw into or through a canvas support to secure a picture to a frame. Do not  do anything that rigidly locks the two together. After you have given an appropriate allowance,  you should not defeat it by locking the picture to the picture frame or weaken  the support by drilling or nailing. One desirable method employs flat metal  strips that attach to the frame at one end, while the opposite end can be bent  over the back of the stretcher bars or the back edge of the panel, as shown in  the illustration above. These strips should be strong enough, after being bent  into shape, to act like springs to hold the artwork into the frame with  pressure.

Another method employs triangular steel spring wire clips (see the illustration  right), which if used in a similar manner will accomplish the same results.

There are two advantages to this method of installation. One is that the picture  is secured, but still allows for expansion and contraction. The other is that  the spring clips or metal strips can be swiveled in or out of place and the  picture can be installed or removed easily without damage to it or to the frame.

3.               Never put the surface of a  valuable piece of artwork directly against wood moulding; use strips of four ply  museum board or felt to isolate the two. It is possible that the finish, gilding, or even  bits of wood might adhere to the surface of the painting. Most conservators feel  that although the felt or museum board may also adhere to the surface, it is  easier to remove from the artwork without damage.

4.               Never put screw eyes into the  support or the auxiliary support of the paint­ing, but into the frame. It is popular today to use thin mouldings to  frame paintings. This makes this rule difficult to comply with. If the painting  is very heavy, and the auxiliary support is required to bear the weight of the  frame as well as itself, it may warp.

Even if weight is not a serious problem, the installation of screw eyes or  brackets may weaken the support. However, if you must screw or nail, drill first  carefully before screwing them in so that the auxiliary support does not split.

5.     Never attempt to  restretch an old canvas or unwarp an old panel. This comes under the heading of  restoration. As a painting ages and  the paint film becomes more brittle, all mechanical adjustments can produce fine  cracks that may not be seen at first. These cracks will inevitably become larger  and more serious. A professional restorer knows how to soften the paint  film carefully to make the necessary adjustments slowly. If the painting is  still in the earlier stages of curing (three months to one year), adjustments  may be made with less risk. This may be done by warming the unstretched painting  on the back with an iron, set on low, to soften the paint film, but be aware  that this will rob the painting of some of its life. Then the painting may be  stretched, but not too tightly. Whenever possible I do this part by hand,  because pliers may exert too much tension, especially on small canvases.

  Spring Wire Clips in Framing










Results of Attaching Hanger to Bars

Additional Notes About  Stretched Artwork

Should the back of a stretched canvas painting be sealed? A stretched work must  breathe, so sealing the back can seal in moisture and dust, which may lead to  mildew. Sealing also prevents easy inspection for the many problems that can  arise. Nevertheless, the greatest dangers to a stretched artwork are dents,  perforations, and tears from accidents and mishandling. If you feel that you  need the extra protection of a backing, there is one method you should consider.  Select a thin board—chipboard, masonite, or plywood, drill holes in it for air  circulation, and place gauze over the holes to prevent dust from entering. This  backing can be fastened to the frame along with the painting either by using  spring clips, or by installing a strainer as shown below.

Stretcher bar keys are little triangular pieces of wood, which are placed into  the inside corner spaces of the stretcher bars and are tapped into place to  force open the corners. This creates slightly more tension, which will remove  sagging and wrinkles. Before hitting the keys, put a piece of cardboard between  the canvas and the stretcher bars. If you slip, you will not damage the  painting. Remove the protective cardboard pieces after you have adjusted the  keys. On older paintings, even small dents may lead to serious cracks over the  years. Just because you cannot see damage now does not mean it has not taken  place. After your protective board is in place, give the keys a few gentle taps.  If the wrinkles do not come out easily, give up!

Although it is rare that stretcher bar keys can  fall out and locate themselves between the inside of the canvas and the  stretcher bar, most conservators will take some precaution against this. There  are two methods. The first one is to place tiny screw eyes in the keys and  support bars and connect them with wire. The other is simply to tape them to the  stretcher bars. The tape method is riskier because most pressure-sensitive tape  adhesives age poorly, weaken, and fail.

Taping Keys










(Excerpt from ART HARDWARE: The Definitive Guide to  Artists’ Materials, by Steven Saitzyk © 1987)