Grounds - Other Grounds for
Rigid Supports

Linseed Oil Emulsion Grounds
Oil grounds and glue gesso grounds can be easily contrasted by noting that oil grounds are superior in flexibility, although they yellow to some extent, whereas gesso grounds retain their whiteness, although they are by comparison brittle. Emulsion grounds, or so-called half-chalk grounds, have been made in an attempt to combine the advantages of the two types of priming. Such recipes call for a glue gesso, made in the usual way except that the filler is composed of 50 percent each of zinc white and whiting, instead of the usual 90 percent whiting. To this gesso, boiled linseed oil is added, in an amount that can vary from about 10 percent to 30 percent of the original volume of the gesso. The oil is stirred in very gradually, and an emulsion is produced of water and linseed oil held together by the glue as an emulsifying agent. These grounds have been recommended for canvas supports in place of white lead oil grounds. However, in my experience, these emulsions have darkened as much or more than have well-made oil grounds, and there is the additional risk that the boiled oil may separate from the emulsion and concentrate at the top of the film. Furthermore, linseed oil emulsion grounds do not seem to be materially more flexible than glue gesso grounds. For these reasons I believe that linseed oil emulsion grounds combine the worst features of both conventional types of ground material. [p. 123]

Polyvinyl Acetate [PVA] Gesso
Polyvinyl acetate [PVA] emulsion is described in the chapter on synthetic resins. Artists have experimented with PVA as a binder for gesso since the later 1940s, applying it to rigid supports such as Masonite Presdwood or plywood. It is more water resistant than glue gesso and can be applied without being kept warm. Methods for the preparation and use of PVA gesso are explained [in the chapter on synthetic resins]. [p. 122]