I have had a few conversations and questions about this substrate I use for about anything I would want to use a canvas for. It's cheap, versatile and lightweight.
I'm going to do a Helen Keller description of this board so you know what to look for if you are interested.
I don't have a brand name, but they call it 'rigid insulate board'. It comes in 4x8 sheets just like drywall. It is 1/2 inch thick. There is a tyvak type paper on both sides with a expanding type foam inside, not styrofoam. You can cut it with a blade knife and snap it just like drywall. One sheet is around $12.00, but will yield boards in any size you would want. I have substrates cut posterboard size down to 2x2inch and my favorite size is 36"x16" for art worthy of hanging over the fireplace. 8x8 works best for shipping (1 oz) in padded envies. It can be cut on the curve too.
First thing you want to do is cover it so you don't ding corners and such. I bought a tablet of gesso canvas paper. I used white school glue, cut box corners and finished both sides. Another way when I know I will end up with layers of mixed medium, I just use gel medium and glue pages of an old book and completely cover it. I do all this covering and mess in one day so that I can store them for later use.
If you have a lumber place that has this stuff, just have them snap cut the big sheet down to 3 pieces so they will fit in the back seat of your car. The coolest feature is that it is so lightweight for shipping or hanging....and being only 1/2 inch thick it can easily be framed.
