In last week’s blog, I discussed various substrates commonly used by pastelists when making their own pastel grit-ground. Once a suitable surface has been selected, it’s time to apply the ground.
There are three components that make up a homemade grit-ground: the “binder” that acts as the glue holding the grit to the substrate; the “grit” that is the source of texture; and “water” that is used to affect the viscosity of the ground.
- Binder: Currently, acrylic-based products are the binder of choice. They retain flexibility once dry and have good adhesive properties, making them very versatile no matter to what substrate they are applied. Acrylic Matte Gel Painting Medium and Acrylic Gesso are two of the most popular. Golden and Liquitex brands are both high-quality sources. Selecting which to use depends on preference. If a white surface is desired or you wish to create a tint by adding acrylic color, acrylic gesso is best. If you don’t need a white surface or wish for the tone of the substrate to show, an acrylic gel matte medium is a better choice. If you colorize the ground with acrylic paint, remember to test the outcome by allowing a sample to dry before committing it to surface. Acrylic colors often dry one or two values darker than they appear when wet.
- Grit: The grit provides the textural quality to the ground. Many unusual products have been used, such as aluminum oxide crystals, various forms of silica, and even kitty litter. As long as it is abrasive and can be adhered to a surface, it can be used. Of all of the grits, the most popular is volcanic pumice. It is available in several grade ratings: 1F is extremely course, 2F and 3F are medium course, and 4F is the finest. Most pastelists use 2F or 3F. If finer grit is desired, rottenstone (a limestone derivative) or marble dust (calcium carbonate) is a good choice. Marble dust also adds absorbency to the ground and is frequently added to gesso in other painting techniques. Ground pumice power is available at many hardware stores in the paint or furniture restoration department.
- Water: To control the viscosity of the ground, water can be added. It is best to not exceed 1/3 by volume of binder and grit combined; otherwise the adhesive quality of the binder can be compromised. To avoid chemical contamination, use filtered or distilled water. Many sources of tap water contain chlorine or other metals that can have a negative effect.
- Recipes: Various combinations of binder, grit, and water can be concocted. A good starting point is: 1 part binder + 1 part grit + 1 part water. For a thicker mixture, decrease the amount of water. For less tooth, decrease the amount of grit. Play with the amounts. It is advisable to experiment until a desired recipe is attained before prepping numerous surfaces.
- Many art supply manufactures are offering premixed “pastel grounds” for the purpose of surface prep. In a future blog, I will discuss the various brands and their characteristics. While I enjoy having the ability to select from a variety of commercially available pastel grounds and surfaces, each with its own unique personality, a major portion of my pastel work will always rely on “homegrown” surfaces. They provide consistency and continuity in an ever-changing commercial environment.
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