Along with conservation experience, Nina usually has her interns do a copy of a master work to better understand traditional methods of making. For mine, I’ll be making a copy of this egg tempera portrait. The funny thing is that this painting isn’t genuinely renaissance. It’s a counterfeit that was made to look authentically renaissance. But, that kind of makes me feel better about making my own counterfeit.
Today we prepared the canvas and ground layer. This process starts with a wood panel that is coated in an animal skin based glue called hide glue. It is sold in a grain form which has to be soaked in water and heated in order to liquify. Once painted on the panel, the glue seals the wood and prevents the ground layer from being absorbed into it. After that, a linen is spread over it. In the old days, sometimes the hide glue was made out of old gloves and dish towels were used for the linen because they were warn and washed enough to assure they wouldn't shrink further.
Nina had me spread it in a cross pattern that is used for all sorts of things in conservation. First, you start in the middle and spread a line across, then do the same thing in the other direction. You should apply enough pressure that the linen becomes a little transparent where you have pressed it down. At this point you should be able to see a cross shape. Then you spread out diagonally from the center of the cross to cover the four corners.
After we painted on another layer of glue, we prepared the ground layer. Apparently in Italy, "gesso" only refers to the white pigment in the ground layer. “Stucco” is the official Italian term for what we Americans refer to as gesso. The version of stucco we made was rabbit glue (similar to the hide glue) mixed with chalk. Instead of actually mixing in the chalk (which might cause bubbles), I dumped spoonfuls of it into the glue and let it sink to the bottom until the level of chalk that settled at the bottom rose to the surface level of the glue. Then I stirred it just a bit, very slowly to prevent bubbles. Applying a few layers of ground to the canvas was the last thing we did, but next time, the canvas will have to be sanded so that it is smooth and ready for detailed painting.