Gesso and Primer
Gesso and Primer
Q: What is the difference between gesso and primer? I have also heard that there is more than one type of gesso?
A: When you paint on a surface with oils, acrylics, tempera paints, or various collage techniques, be it a canvas, panel, or paper, you must first prepare that support with a coating that has the ideal properties to hold onto the paint. This coating keeps the paint from coming into contact with the support. This insulating layer is called a “ground.” Paintings should not be done directly on a canvas or panel without a ground because if the support deteriorates it will damage the painting. Sometimes a conservationist is required to separate a painting from its support if the later is no longer stable. If the painting is attached directly to that support you can see how this would be problematic. This does not apply to watercolor paints or pastels which are attached directly to the paper. There is the issue of the various names for the different types of grounds, and sometimes this can create some confusion…
“Gesso” is the name of the traditional ground made of Calcium Carbonate (chalk) and Hide (animal) Glue. It is not flexible and can be only be used on rigid supports. Its use dates back hundreds of years and was a favorite of Tempera painters who loved to have a very smooth finish. Some artists still use it for this reason and it can easily be made at home with materials available in most art stores. It can be built up and sanded between layers (as many as 30!) to create a painting surface that is almost a smooth as glass. In recent years manufacturers of acrylic paints have been making Acrylic Polymer Gesso and this product has all but replaced the original variety. It too is called simply “Gesso” most of the time. It uses polymer resin as a binder instead of hide glue so is more flexible and can be used on either rigid or flexible supports.
”Primer” is the name used to denote a lead-white-in-oil ground used for oil paintings. For centuries painters used the Hide Glue Gesso on wood panels, or a Lead Oil Primer on canvases. Now the Acrylic Polymer Gesso has replaced both for most artists. Most art supply stores will sell an oil based primer and some manufacturers have changed the original formula by substituting Titanium and Zinc for the lead white pigment and Alkyd Resin for the Linseed oil. Still others have simply used zinc and/or titanium instead of the lead white and use Safflower Oil instead of Linseed oil. This last formula would not be as flexible or durable as either of the other two. It helps to check the ingredients of the various products before you buy.
So “gesso” refers to the water based grounds, that is, the traditional hide glue/calcium carbonate or the modern acrylic polymer variety, while “primer” is the name reserved for an oil based ground for oil painting.
