SIZE: A dilute solution usually, hide glue, applied to the support surface of a painting
in preparation to subsequent layers of ground or paint.
Size may work to enhance the adhesion of subsequent layers as in the case of traditional gessoing.
Size may work to protect the support as in the case of oil grounds on linen.
It may also reduce the absorbency of a ground layer as in oil techniques on traditional gesso.
Weak shellac is often used as a size in this application.
Application of the size is referred to as "sizing".
GROUND: A painting is a layered object. The ground is a preparitory layer which covers the entire surface
of a previously sized support. Grounds are specfic to the support.
1. Gesso, a ground made up of hide glue and an inert filler such as chalk or gypsum, is the desired choice for wood panels.
2. Traditionally oil ground, a ground made up of oil and pigment, is the ground of choice for fabric supports.