Materials and Methods: Supports

In past postings there has been substantial information about paint (both oil and casein) and about brushes, but not much about other basic subjects like supports, grounds, sizes, or other more technical information. This post begins a series summarizing what I know about constructing a painting, from the ground up. Today's subject is the materials that oil painters use to paint on--known as supports--and how they are prepared. Future posts will deal with other technical issues.

Birch plywood is excellent for oil painting (Photo: Rockler Co.)

Supports
A support is simply the material painted upon and for an oil painter that can mean a wide range of materials. Here are common ones.

• Fabric - Many call any cloth used for painting as "canvas" but that isn't strictly correct. Canvas is by definition made of cotton. In reality other kinds of cloth can be and are used. Linen is considered by many the finest sort of painting surface, but polyester or polyester/cotton mixes are also useful. Whichever one uses, it is either stretched on a wooden chassis or glued to a wooden panel for added rigidity.
• Wood - One of the original surfaces for painting, wood supports today may come in various forms. Hundreds of years ago, wooden panels were made by experts who could cut them very thinly and prepare them for the master painters of their time. Some artists did their own panel cutting and preparation or had it done for them in their own shops but many purchased them from specialists. Very large panels were sometimes fabricated from smaller pieces, again commonly by special craftsmen. Today there are two kinds of wooden supports most commonly used:
• Hardboard (the material trademarked as Masonite long ago) is widely available. It is made under intense pressure by compressing wood fibers. Hardboard can be purchased in home improvement stores in large sheets then cut to appropriate sizes and prepared, or you can buy various kinds of commercial painting panels that are hardboard-based. Hardboard in appropriate thicknesses doesn't warp appreciably when prepared correctly, remains dimensionally stable, and is easily prepared. Most of my experience with rigid supports involves hardboard.
• Plywood is made by layering veneers of wood (veneers are thin sheets) perpendicular to one another and compressing enormously, providing stability. Plywood can obviously be made from various sorts of wood, but for painting purposes many use Baltic birch or other hardwood. Plywood is more stable the more plies are included. Thicker plywood is less likely to warp but thinner panels may need to be "cradled"--supported by an attached wooden chassis behind the panel.

• Metal - Sheets of metal have been employed as painting supports for centuries. Copper in particular has continued to be a choice of many painters, but aluminum is also suitable, and lighter. The weight of metal clearly limits the size of the painting. Steel, for example, accepts oil paint well but is very heavy.
• Plastic- Although I've little personal experience, many have tried various plastics as supports for oil painting. In particular, ABS (acrylonitrile butadiene sytrene, for the science-minded) was used widely a few years ago, but these days it may be employed less often. Quite a few other kinds of plastics have been used over the years but I've little information or interest in those.
• Paper -  When I was learning I was told not to use oil paint on paper because the oils would eventually degrade the paper fibers and destroy the work. Others have said that using oil paint on decent, heavy paper like watercolor papers or others is fine so long as the paper is properly prepared, or "sized". Paper can be prepared for oil paint by priming with a coat of acrylic primer (commonly sold as "gesso") or acrylic matte medium. The acrylic layer will remain flexible, and accepts oil paint readily. Paper is lighter, cheaper, and quicker than other supports and if the results are acceptable the paper can be glued to a rigid support.

Linen on Gatorboard (Photo: Atlanta Art Solutions)

Of course, if one doesn't want to make supports, there are any number of products available that are already prepared and ready to use. These are the two kinds that I've used. A search on the internet will reveal many others.

• Gesso panels - Hardboard panels in standard framing sizes are available from a number of sources. Typically these panels are manufactured by spraying gesso, either in the traditional formulation or made with acrylic binder and marble dust. Either way, these panels come to the artist finished with a smooth white surface that accepts paint well. 
• Fabric panels - Panels of this kind are made by gluing linen or cotton fabric to a rigid support. The rigid support could be hardboard, fiberboard, aluminum, Gatorboard (above), or another kind. Whatever the rigid support, the fabric is typically prepared with at least two layers of white primer, either acrylic or oil-based. 

Acrylic gesso (Photo: Liquitex Corp.)

Grounds
If you're making your own, once you've chosen the kind of support you want for painting it has to be made ready for paint. Some surfaces require very little preparation while others need quite a bit, but obviously the paint must adhere well as remain in place for a long time. Another word for a ground is primer. A surface that's too smooth may need to be rougher (roughness is called "tooth") or if too rough may need smoothing. One that's too absorbent needs sealing, and so on and of course the ground must adhere well to the support.

• Gesso is Italian for chalk. Traditionally wood panels were prepared for paint by priming them with gesso, which can still be made of the traditional ingredients of hide glue and gypsum (or other chalk). The material sold today as gesso is actually an acrylic product. You can buy the traditional materials and make your own gesso, but hardboard panels with gesso or white acrylic priming are widely available. 
• Acrylic "gesso" primer is made with an acrylic binder and white marble dust. The products available are clearly labeled as acrylic material. They work well and are available in colored formulations too. 

Sizes
Sizes are often discussed in the context of painting on paper. These are similar in some ways to grounds. That is, these are compounds that are used with paper (mostly, although cloth is often sized) to reduce or eliminate its absorption. The idea is keep oil in paint or ink from making intimate contact with the paper fiber. Sizes also promote durability and flexibility. Sizes in paper also provide adherence to any priming additionally applied. 

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Previous posts dealing with materials:
Brushes Part 4 (includes links to Part 1-3)
Paint Basics
Milk Paint
More on Milk Paint
Casein Investigations