Everything you ever wanted to know about oil painting grounds but were afraid to ask. What are the choices, which one is best and why, which is best for me?
Tradition ‘Gesso’, also known ‘glue gesso’ or ‘Italian gesso’ is a traditional mix of an animal glue binder (usually rabbit skinned glue, chalk, and white pigment, used to coat rigid surfaces such as prepared wooden panels as an absorbent primer coat for oil painting. Mixing and applying it is an art form in itself as it is usually applied 6 to 10 extremely thin layers.
The standard hide glue mixture is rather brittle and susceptible to cracking, thus making it suitable for rigid surfaces only. For priming flexible canvas an emulsion of gesso and linseed oil, also called ‘half-chalk ground’, is used. Gamblin, Williamsburg, and others make semi-traditional gessos in both Lead and Titanium White Pigments.
Modern ‘acrylic gesso’ is a widely used ground that is a combination of calcium carbonate with an acrylic polymer, medium ‘latex, a pigment and other chemicals that ensure flexibility, and increase archival life. It is technically not ‘gesso’ at all.
It is sold premixed for both sizing and priming panels and flexible canvas for painting. Though manufacturers of acrylic gessos often tout its use on a stretched canvas we do not totally concur ‘see below’
The Painter’s Handbook notes a problem with using oil paints over an acrylic gesso ground instead of a traditional oil ground, citing a mismatch in flexibility over time that could cause the oil paint to delaminate.
This is an inconvenient truth for manufacturers of Arcylic Gessoss who have gone to extreme links to blame the pigments (most notably Zinc White) and the not the Acrylic Ground for isolated problems of delamination. Most of the delamination problems are not caused by a particular pigment they are caused by painting on an Acrylic Gesso Ground that was not dry. It takes one to two weeks for an Acrylic Gesso Ground to be dry enough to paint on.
Manufacturers know the downside of using an acrylic gesso is that it remains more flexible then oils in its dried state. This difference in flexibility can cause cracking down the road. They know one should use acrylic grounds for oil painting only if they are working on a rigid substrate.
The bottom line here is that zinc white and lead white are not compatible with Acrylic Gesso grounds, especially on flexible substrates. Acrylic Gessos absorb the binder out of Lead Whites which can lead to crackling. Acrylic Gesso provides a mechanical bond ‘tooth’ and Zinc White requires a chemical bond ‘cohesion and adhesion’. Neither should be used directly on an Acrylic Gesso Ground.
Many oil painters today use PVA size (Archival Bookbinders Glue) on their canvas. PVA or polyvinyl alcohol sizing provides the same sealing properties as rabbit skin glue. Its advantage is that is doesn’t absorb moisture from the environment like Rabbit Skin Glue. This helps to reduce the chances of the paint cracking or delaminating from the ground.
If one is a professional painter and concerned with archival materials one should most definitely use oil-based grounds. It is also highly recommended to use professionally prepared grounds on rigid substrates. If one is using stretched canvas it is even more important that they use professional-grade materials. For panels, we prefer Raymar and Masterpiece and for stretched canvas Masterpiece. Oil-based Grounds are the best, PVA comes in second and Acrylic Gesso third in regards to longevity. Most of the problems concerned with crackling or delaminating are mitigated by using professionally pre-prepared panels and canvases.