Since the inception of the Pastel Pointers Blog nearly six years ago, one of the most frequently ask questions I hear concerns how best to mount pastel papers in advance of wet underpainting techniques. Artists that utilize a wet painting technique on a paper surface understand the issues involved in retaining a flat working surface. This has lead to procedures involving sizing, stretching and mounting of paper prior to painting. Retaining a flat working surface is especially pertinent for the pastelist that works with underpainting techniques involving wetting pastel or any number of other mixed-media applications. If, when wetted, the pastel paper wrinkles and dries irregularly, a subsequent application of pastel can prove difficult to achieve. When deciding whether your pastel paper should be mounted (historically referred to as “laid down”) it’s helpful to consider the wetting agent to be used and the physical properties of the paper.
Wetting Agents: Various techniques can be used to disburse pastel across a paper surface. One of the most popular is to wet a thin layer of pastel with a brush and solvent. There are three basic solvent categories: water, alcohol (isopropyl/denatured) and odorless mineral spirits (paint thinner). Water swells most paper surfaces. For paper to remain flat, it needs to be of heavy card weight, sealed with a nonabsorbent sizing, or mounted to a strong substrate in advance of wetting. Whether using pastel with water, or any number of other water-based media techniques, the wrinkling effects of water have to be considered. Alcohol has a percentage of water, but due to its rapid drying time, it tends to not wrinkle most papers unless it is heavily used. Alcohol can, though, soften certain acrylic-based products and should be tested on pastel papers formulated with an acrylic binder before painting. Odorless Mineral Spirits are capable of beautifully disbursing pigment and have no swelling effect on most papers but the solvent is derived from petroleum byproducts, and—due to health concerns—many artists avoid using it.
Paper Properties: While alcohol and mineral spirits have little swelling effect on most fibrous papers, water is another story. This is especially pronounced when the paper has a high cotton rag content. If water is to be used, consider a paper weight close to 300 lbs. The heavier the card stock, the less prone to wrinkling the paper will be. Another consideration is papers sized for print-making, such as etching papers. These papers are impregnated with a sizing that makes them lie flatter once dry. The degree of final flatness is dependent upon just how wet the paper becomes during the underpainting process. If you’re in doubt about a paper, take a small sample sheet and wet it with the solvent you plan on using. Watch the effects and plan accordingly.
If, after consideration, a mounted (laid down) pastel paper is best for your needs, there are a number of ways to proceed. In next week’s posting I will discuss a couple of do-it-yourself options.
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