*Matting Board
This material is used in framing Watercolors or Photographs.
It is available in a huge range of colors & textures and is quite good to Pyrograph onto.
Any framing shop will have it in stock and it is not expensive.
I actually picked up some work from one of these shops after they saw what I was using it for. I was commissioned to burn a family crest onto the matt board of a photograph of a old colonial home they were framing for a client.
The finished work looked great and their customer loved it.