Looks like metal but light as a feather which, of course, makes it easier to glue to your art. I love the Holbein metallic gessos so thought I would cast it in a silicone mold I had made from a religious piece that I got in Mexico. This was left on the mold overnight to dry.
To learn about this technique than what I am showing you here, read the March/April issue of Cloth, Paper, Scissors.
When you peel it from the silicone mold you will have a flexible skin of silver gesso.
I aged by applying a wash of burnt umber over the silver. Now it is ready to be glued to a painting.