Egg Tempera used in Fresco painting
Recently, I took a wonderful bon fresco workshop taught by George O’Hanlon the owner of Natural Pigments. While I’d first taken a workshop in fresco ten years ago, the depth of knowledge and expertise that George brings to the medium made the experience a very rich one. I’d heard of “al secco” painting in fresco, essentially, working on “dry” plaster. Unlike bon fresco, where the pigment becomes attached to the plaster through a crystallization process, al secco works with a binder like egg, casein, or glue on the next day. My assumption about al secco painting was this layer was painted on the cured plaster to touch up details after the giornata (day’s work) was already dry. In fact, al secco refers to a window of time following the giornata when the plaster is still capable of accepting paint providing there’s a small amount of binder added.
Unlike traditional egg tempera painting, in al secco, the portion of egg to pigment is very small. Also, the paint itself is very fluid and thinly applied—like thin layers of stain. This layer can be painted for up to two days on the drying plaster. After that time, the bonding with the plaster stops and any paint applied will be just a surface treatment. This surface treatment of paint is what can become so fragile over time and flake or rub off. Whereas true al secco paint applied within two days is permanently bonded with the fresco enriching the nuances of the surface.
I have painted in egg tempera for 25 years, and I’d thought I’d understood its applications and limitations fairly well. However, seeing a stroke of thin egg tempera soak into a layer of plaster was a treat. It is difficult to explain just how wonderful the paint flows, how it is accepted and how subtly it modifies the surface. These properties of course were well known in the early studios of the Renaissance. Like a rare instrument sounding once again, I felt the unique voice of egg tempera reminding me just how special it is. Nature’s most perfect emulsion, the egg, acting as the agent between drying plaster and a closing window of time. Remarkable.