Hi. It has been my experience that most sample boards are too flimsy for plasters. My local big box store carries smaller sheets of drywall. I think they’re 1/4”. I just cut them to about 15x15” and use that. After the plaster is applied and dry, I run some cheap masking tape along the raw edges and fold it over so the gypsum isn’t flying everywhere.What do ya'll use most often for sample boards? If you do plaster work (lime plaster finishes) is there something from a big box store that works well?
I've been buying my lime plaster (grassello, etc) boards through the rep for my plasters but it add's considerable cost....
As for other samples, you can check out dickblick.com for illustration board. I use Crescent 053116, but I still prime it with Bin before paint.
Also, you can check these out, they work well. Good luck.