INFORMATION JUST PAINT SHEETS 8/07 No. 3 Developed in collaboration with Conservator James Bernstein and Golden Artist Colors, Inc. Stretching Unprimed vs. Pre-primed Canvas for Painting Pre-stretching traditional size. A stretched linen canvas by the weave in an unfavorable position. It is itself on a humid day would become taut. wisest to pre-stretch as a separate step. This Unprepared Canvas When there is an animal glue size on a linen aligns the weave as fabric tension is For ultimate fabric choice, unprimed canvas, the animal glue swells and the canvas estimated. If a fabric is very responsive, the canvas offers the most possibilities. The becomes less tight. Conversely, a linen first stretching may be done barehanded artist is not limited by the variety or size of canvas by itself on a dry day would become (without pliers), as the canvas should not fabrics available pre-primed. limp. However, animal glue under dry initially be stretched too taut. Allowance has If starting with unprepared linen, cotton, conditions shrinks and becomes taut. Thus to be left for subsequent wetting and rinsing or other fabric for painting, preliminary the opposite natural behaviors of linen and that will tighten the fabric significantly preparation of the canvas is essential. A animal glue are dynamically opposed and (albeit temporarily). common misunderstanding is that the help hold each other in tow. The pre-stretched canvas should be application of size or ground layer coatings This dynamic is not as well balanced for gradually and uniformly moistened and then will correct or compensate for all sorts of cotton canvas. Cotton differs from linen in thoroughly wet. A garden hose, with the inadequacies in canvas stretching. This that it often becomes limp instead of tight nozzle set for “fine mist”, is effective for the simply is not true. Pre-stretching is the step on a damp day. This is especially true for overall misting the fabric. The nozzle is then often omitted that will insure a canvas of unsized cotton canvases where passages of adjusted to “jet” and the canvas is showered superb suspension. the cotton are left uncoated. aggressively, front and back, for a few When a natural fiber canvas is thoroughly Acrylic dispersion mediums and acrylic minutes. (This step is best performed wet with water, the fiber bundles swell. This grounds (which = acrylic dispersion + outdoors). The wetting of the canvas will causes the threads to fatten and shorten, and pigment) behave differently from natural cause the threads to fatten and swell, making the canvas becomes dramatically tighter. animal (rabbit skin) glue sizing or grounds. the canvas extremely taut. IT IS This tightness is short-lived; upon drying, Upon drying, they are not comparably IMPORTANT not to do an overly tight first the canvas relaxes again. If wet without contractive. They are not as responsive to stretching: the tremendous contractive forces being under constraint, a fabric will shrink, humidity changes as hide glues, but remain from wetting could cause thread slippage, but will also distort, then dry unevenly. If quite responsive to humidity shifts breakage and stretcher splitting. wet while under restraint, as in a stretched nonetheless. They relax and become more After washing, set the stretched canvas mode, the fibers will slip a little from the plastic under high humidity and become aside, off the floor on foam blocks, to temporary shrinkage, and upon drying the much tighter in low humidity. They will not dry thoroughly. canvas will become slack again. However, be resoluble with water should the canvas With orientation accomplished, the having been acclimated by pre-stretching, become wet, are not as vulnerable to canvas may then be re-stretched with an the threads will be nicely aligned in their cracking, and are not nearly as susceptible to exceptionally good estimate of final respective directions. The fabric tension, bacterial attack. Acrylic sizing is generally canvas tension. although limp, will have a lot more evenness bulkier than animal glue sizing. This helps to to it. fill in and lock the weave. Second Stretching Traditionally, pre-stretching is abandoned. The concentration (the strength of the After pre-stretching and wetting, the The artist goes directly to the final solution) of animal glue or acrylic sizing has canvas will be wrinkle-free, nicely aligned stretching, wetting and sizing the canvas in a major effect upon canvas tautness. Some and significantly limper than when first one step with animal protein glue size. The artists rush through the stretching phase, not stretched. The canvas is now ready for the canvas shrinks when wet and upon drying, paying particular attention to tension “true” stretching. The second stretch is wants to become limp, however a contractive applied or the tacking interval, spacing tacks performed as the first stretching, except this glue size has been introduced to fill some of or staples too widely apart (say 3” to 5” time canvas pliers will be needed for the space between threads, to seal the outside between staples). They then look to added pull. of the threads, and to pull the canvas taut, compensate by strengthening the Even on the second stretch, I recommend counteracting the natural inclination of concentration of animal glue size to get the securing the fabric with pushpins. It is the canvas. canvas to pull adequately taut. wisest to set aside the stretched canvas This sets up an interesting symbiotic The danger in all of the above is pinned on its stretcher for a day or more relationship between the canvas and stretching and sizing simultaneously, locking before setting with staples/tacks. With climatic shifts and the passage of time, the longer responsive nor forgiving to pulling, weave is locked in place; there is not a lot of canvas will relax and settle onto the stretcher, pushing, rolling or creasing. If a primed give or play in the fitting of the canvas onto giving a true indication of how even or not canvas is flexed or abused, the internal a stretcher. Too much pulling, stretching or the stretching is. If puckers, draws or slack structure of the fabric and ground will be sharp bending will over-part the priming and passages appear, the pins may be removed broken and continuity/cohesiveness will be produce cracks in the ground and breaks in from those locations and the canvas re- lost. Such disruptions will develop as cracks the fabric. As with any material, coaxing stretched as needed. in the priming; even if painted over, the and encouraging it to respond, rather than The pins should not be removed from the cracks will work their way upward or make forcing, will produce the best results. stretcher edges until the canvas is completely their presence known. The crack by itself is If performed well, only one stretching may stapled or tacked. Only then may the sizing not the only unsatisfactory aspect of the be needed. and/or ground coatings be safely applied. alteration. Once continuous tension is For further discussion and resources These coatings will ameliorate some of the broken in a canvas painting, cupping or regarding canvas preparation and canvas texture, especially if several layers of forward curved (concave) lifting of ground stretching, see: acrylic ground are applied and smoothed and canvas often occurs on the faces adjacent Bernstein, James. A Remarkable Way to into the weave in the process. to the crack. These planar distortions are Stretch Canvases (and other Essentials of readily disturbing when oblique (raking) Canvas Preparation). Stretching Pre-primed light traverses the painting, accentuating the JUST PAINT New Berlin, NY: (Gessoed) Canvases crack patterns. Golden Artist Colors, Inc. Issue 17, Commercially prepared primed canvases September 2007. An uncoated textile is extremely flexible are the most straightforward to stretch, as and forgiving. It may be pulled, pushed, the fabrics have been pre-aligned (to James Bernstein rolled or folded without substantial varying degrees), pre-coated and smoothed September 2007 ramification. Once coated with sizing and with sizing and ground. Upon purchase, www.jamesbernstein.com ground layers, however, a canvas is changed they are ready to “stretch and paint”. into a multi-ply, laminate construction. The Because they are sized and primed, the fabric weave is now locked in position. It is no .