Quick question. The darker brown board - what is it?
It looks like the back side of hardboard, a fiberboard. Is the other side smooth and shiny?
Unfortunately I can’t see the other side, as it’s under several layers of gesso. It was made to be a surface for painting with egg tempera, if that helps…
It is masonite
Yep, hardboard for painting is definitely a thing
(edit: looks like Utrecht lists both Masonite and plywood under “hardboard”. Agree with Joe yours is Masonite)
Yup, masonite! In some of my college painting classes we used this and did layers of gesso to get it paint ready.