When a client brings a painting to Lowy for conservation, it may sometimes require lining—a procedure whereby another canvas is adhered to the verso of the original to consolidate tears, stabilize lifting paint, correct surface distortions or provide structural support to an oxidized or damaged canvas. A variety of materials and treatments are used in this multi-step process providing a range of options so that the least invasive approach may be selected to ensure that a painting is structurally stable.
When treating a painting for structural problems, Lowy's conservators first carefully apply humidity, heat and pressure on a vacuum-hot table to mitigate any surface distortions. The canvas verso may then be infused with the thermoplastic Beva 371 to further stabilize the painting. Recognized by conservators worldwide as the preferred adhesive for lining, Beva 371 was developed by the renowned conservator Gustave Berger, who worked for Lowy in the 1960s and trained Lowy's chief conservator Bill Santel. In the past, adhesives such as wax and animal skin glue were used for lining paintings, each of which has specific drawbacks. Because wax thoroughly permeates the paint and canvas layers, it can cause the ground and paint layers to darken. Also, when beeswax is used, its chemical properties tend to reverse the natural hardening of the paint layers over time, making them more soluble and, therefore, less resistant to solvents used for cleaning. Animal skin glue, on the other hand, is a strong adhesive that can create tension between the original paint and canvas layers, causing the paint to flake or crack. And because it is an organic material, it not only dries and hardens with age, thereby losing its original adhesive strength, but can also attract detrimental molds and other parasites. Additionally, neither animal skin glue nor wax can be easily removed during later conservation treatments. Beva 371 is an inert, reversible substance that does not add extra tension to the support or cause a weakening or visible darkening of the paint layers. For these reasons, it is the preferred adhesive of conservators today.
Once the canvas has been infused with Beva 371, the decision may then be made to line the painting by applying additional layers of structural support, if necessary. In this case, Beva 371 also serves as the adhesive between layers. Lining is typically employed when a painting is either structurally weak and/or suffers from large tears or distracting surface distortions which can be caused when the stretcher bar support exerts too much pressure on the painting. Extensive flaking, cracking or cupping, whereby heavy paint layers can be seen lifting off the canvas, also often necessitates lining. In all cases, the client, in cooperation with Lowy, must weigh all factors to determine how much treatment is necessary. For example, if the painting is structurally stable yet displays minor surface distortions, then the client may opt not to line, even though the surface distortions may not be completely corrected using other treatments. Lowy offers a range of conservation materials and methods as options so that the treatment can match specifically the needs of a particular painting. In all lining procedures, Lowy's conservators favor the "less is more" approach that is consistent with today's conservation standards. For example, Lowy's conservators can use Beva to apply a layer of silk Crepeline, a transparent natural, stocking-like material when the existing support is fairly stable so that any markings and signatures on the verso remain visible.
If a painting requires more support, then Lowy's conservators will apply a lining canvas. But first, a synthetic Pecap interlayer is always inserted between the original canvas and lining canvas for extra strength and durability. In more challenging cases, a DuPont Mylar interlayer may also be inserted. This plastic sheet, which is occasionally used when a painting displays large tears and/or severe cupping, provides even more structural support. Conservators typically use either a linen or synthetic canvas for lining, depending upon the density of the artist's ground and palette and on the client's individual tastes and preferences. Some clients prefer the irregular, natural look of linen to the smooth, uniform appearance of a synthetic material. But there is a downside to using a linen canvas for lining. Because linen is an organic material, it oxidizes and weakens over time, thus it may require with time the painting to be lined more often. Also, the irregular surface of linen, with its bumpy knots, can create planar distortions on the paint surface. Synthetic lining canvases are available in a range of weights and in darker or lighter beige and gray tones, which are inspired by the linen canvases traditionally used by artists prior to the 20th century. The heavier synthetics provide more support, whereas lighter weight examples often work best with small paintings. Lighter toned synthetic linings tend to complement contemporary paintings, many of which are executed on less expensive cotton canvases. Many contemporary art collectors prefer synthetic linings to cotton linings because of their greater durability. Unlike linen and cotton, synthetic linings do not oxidize or deteriorate over time, and therefore do not lose their tensile strength. Consequently, paintings lined with synthetic canvases are less likely to require future structural interventions. After the appropriate materials and treatments have been applied to the original canvas stabilizing it for future generations to enjoy, the painting is ready to be re-stretched on its stretcher and enter the world with a vibrant new life.