Gesso 101: A Gesso Primer part 1 of 4
Welcome to our first Bloginar (Blog Seminar). Please have a seat we’ll begin presently!
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PART I: What Is Gesso? (The Historical Undercoat)
Gesso is an Italian word meaning simply “Chalk” or “Board Chalk”. The substance we today call Gesso has existed in one form 
or other almost since the beginning of time. That may be a slight exaggeration. It has however been noted by historians that Gesso was being used as early as thousands of years BC, and certainly as long as anything man has created that can be equated to modern day painting. The history of Gesso, as one might imagine, is intertwined with the history of painting itself. The actual origins of ancient ‘Gesso’ are mysteriously unknown. It is however widely believed that the origins of the products we use today called Gesso, originated in Italy.
The ground (or base substrate) on which 13th- and 14th-century Florentine artists painted was usually a ‘Plaster-of-Paris’ -like mixture, known as Gesso. The method of preparing a ‘panel’ was first to fill all the cracks and crevices in a Poplar, Lime, or Willow panel, with a mixture of size (a sticky binding substance made with glue, wax or clay) and sawdust. The panel was then covered with a piece of fine linen cloth, which was kept in place with size, and this surface was coated with heavy Gesso, known as “Gesso Grasso”. Finally, a lighter Gesso coating called “Gesso Sottile”, which provided the painting surface, was laid on with a brush.
In Geology, the Italian “Gesso” corresponds to the English “Gypsum”, as it is a calcium sulfate compound, thus ‘Gesso’ is literally a powdered form of the mineral Calcium Carbonate widely used in art. Gesso (chalk powder) was traditionally mixed with animal glue to use as an absorbent primer coat for panel painting with tempera paints (the earliest form of painting known which can be equated to modern day painting). Originally Gesso provided a permanent and brilliant white substrate, as long as it is used on wood or Masonite. This mixture was/is rather brittle and susceptible to cracking, thus making it unsuitable for priming canvas.
Flash forward… (A cheap literary trick -but effective just the same)
In 1955, an Acrylic paint company called Liquitexdeveloped the first water-based acrylic Gesso. Modern Gesso is a mixture of calcium carbonate with a pigment and an Acrylic polymer medium, latex. The pigment added is usually titanium dioxide or titanium white; along with other chemicals that ensure flexibility, and ensure long archival life.
Modern gesso retains the absorbent qualities of older gesso but is more flexible, and can therefore be used very efficiently on canvas. It can also be colored during the manufacturing process by replacing the titanium white with other pigments. The artist can also color the Gesso using watercolor, acrylic paint, or another coloring agent, in order to tint the surface to be painted. Canvases with Gesso pre-applied are commonly available commercially.
We get the picture that Gesso has indeed had a long illustrious (and lustrous) history.
Check back soon for PART II: Gesso For The Artist (The Foundation Layer) the next installment in our mini ongoing bloginar - Gesso 101: A Gesso Primer.
Tags: acrylic mediums, gesso, history gesso, Liquitex