The Importance of Properly Preparing Canvas

March 1, 2016

The following story illustrates why a properly prepared foundation is essential to the long life of a good painting, given the vicissitudes of travelling, storage and viewing space to which it will almost certainly be subjected. It also shows what Conservators know well, that time and chance, travel and weather, can do to a painting not put on a really good foundation to start with.

During the year 1944 as a young boy I often watched my Mother (Sybil Hill) working at painting a large pastoral scene for the United Church in a small town in the Okanagan Valley, British Columbia. She did it on large masonite boards, fitted together to make a shape like a church window maybe 6 feet wide and 10 high. She was a good artist, taught and respected by Fred Varley, AY Jackson and Arthur Lismer. Some 25 years later I got a call from the people at the the church, they were removing the painting and wondered if I wanted it. I travelled to BC, packed it up and had it shipped to Ontario, where it has been stored in various places since. When I got it then, in the early ‘70 s, it already showed signs of deterioration. Mostly moisture damage from humidity getting into the masonite, softening the front and causing small chunks of paint to flake off. That deterioration has become worse over time. It would need a major restoration job, now, 60 years after it was painted, if it were to be hung anywhere again.

A fine painting, no matter how well or expertly done, or how beautiful, like a fine house, starts with a good foundation. Upper Canada stretchers are used as that foundation by hundreds of professional artists and conservators throughout North America. They are designed and made with a great deal of hand work to be the best available at a reasonable price. Using Upper Canada Stretchers, you can be sure your paintings will have the beginning they need to last at least as long as the canvas and even longer if you follow the time-tested canvas preparation directions described below. What’s more, you have the pleasure of putting together a stretcher frame which is easy to assemble, perfectly square and rigid, and stays flat and square under any tension you care to use in stretching your canvas.

As a professional you know how your energy and creativity is supported by having excellent, responsive tools. The work of artists is undoubtedly a lot more of art than of science, although today science has a lot to contribute. Nevertheless, good artists have always done a lot of experimenting, and relied on their own experience for decisions about materials and how to prepare and use them. So nothing here is to be construed as anything but a guide, a starting point for building or adding to your own expertise.

Our Conservator and professional artist customers have taught us what it takes to make a great keyable canvas stretcher frame:

  • several unique profiles in a variety of configurations to suit any need
  • deep slope or “fall” on the front face avoids unwanted canvas contact
  • hardwood maple keys ridged so they grip in the grooves
  • long rounded radiuses protect canvas at the edges
  • select grade kiln-dried wood and precision-cut custom work to make a perfectly square, easy to assemble, flat rigid frame that takes any desired level of tension in stretching without warping or bowing.

Here is an excerpt from some technical notes on stretchers by the Australian Conservation Society, I have augmented their ideas with some information gleaned from our experienced customers.

For the last five hundred years or so in Europe and elsewhere, canvases have been stretched over wooden frames for painting. This technique became a popular alternative to wooden panels as it allowed artists to create large transportable paintings with a minimum of preparation time and expense.

The stretcher is, in fact, a complex construction which must be well made and finely “tuned” to meet the requirements of a flexible canvas. Artists for many years have painted on canvases stretched on keyable stretchers for a number of good reasons. If the painting is on boards, these are liable to crack as they dry out, or swell and distort or even tear the painting if there is moisture in the air. They are also susceptible to dry rot and insects! And a solid board of a large size is very heavy.

A necessity in a high quality stretcher is the use of wooden keys to maintain tension in the canvas. A weakened and sagging canvas easily causes damage in aging paint layers.

Poorly made stretchers may exhibit; insufficient or no beveling on the front face, no key slots, inadequate cross bracing leading to warping or twisting of the frame under tension, recessing of cross bracing too close to the canvas, fixed or poorly made joints, and corners out of square. These deficiencies contribute to the faster deterioration of the canvas, ground and paint layers.

Preparing the canvas or linen surface:

Sizing with acrylic gesso, or “flake” white (contains lead,not healthy!) seals the canvas against moisture penetrating from the back. If it is hard enough, and yet flexible enough to avoid cracking it becomes a stable base to support the whole paint layer when many years in the future, the canvas has deteriorated (as it may well do in time, which often has the same effect on paintings as it certainly does on people), and the entire painting must be transferred to a new canvas by a painting conservation expert.

Canvas may shrink under the gesso treatment and become over tight and ¯warp” the frame, or it may relax, and require the frame to be “keyed out” to retighten it.

Maybe it would be a good idea to try, on a smaller canvas, a few of the preparation ideas to see what works best. Experience says that every type of canvas and linen is different, especially made by different manufacturers, and whether preshrunk or not, treated somehow, or not. Careful professionals will experiment with a new canvas or linen to see how it behaves, before using it to support a valuable, important painting.

The experience of our many customers is that our stretchers, with proper cross bracing, will easily stand enough tension that there is no worry about “ghosting” from the cross braces while painting. This is provided the canvas is a good quality cotton duck, properly prepared with one or more coats of gesso. Initially, the canvas should be stretched snugly, but not with a lot of force, with canvas pliers, but without driving in the keys. Any tendency of the frame to twist can be controlled by judicious tightening of the different corner keys, and cross brace keys. You can stop the keys from dropping out (which they may do before they are driven in somewhat) with a bit of sticky tape. Then, if the canvas begins to sag later under the weight of paint, or after priming, you can tap in the keys to restretch the canvas.

Donato Cianci, Nov. 8 2002

Here is quote from one of our customers that illustrates how good stretcher bars can help artists do their best work.

“Hi Donato. We talked a bit when I placed an order for some stretchers (the biggest set was 7 1/2 by 4 feet), and I said I would drop a line to tell you how they worked for me. Well, I’m very pleased with them. At first I was concerned about the softness of the wood, but after stretching a piece of linen four times over the large bars (literally tight as a drum) there is no perceptible warping or even strain on the form of the bars or stretcher as a whole- very nice. It seems like the softness of the wood is a plus – it definitely takes the tacks better than hard woods. I can’t tell if the wood is better (straighter grained or something) or if the superiority is in solely in your workmanship, but I’m glad I know about your company. Thanks, Oliver Benson”

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