When you do pyrography the bottoms of the profiles can get a little burnt, especially when doing the the deep stuff. If you are going to paint the finished product a light colour, it can often bleed through. To prevent this I coat he area with a sandable sealer which gets into the crevices and prevents bleed through before painting. Here's my chicken girl after an application of sealer.
Automata is a creative blend of my life interests , engineering, art and woodworking.