I made one of those big boards with canvas and one layer of cotton batting and I really LOVE it!
But when I'm doing a lot of steaming or starch preparation, the batt gets saturated in spots, so I know it's transferring to the OSB.
I'm thinking that the next time I make one of these, I will cover the top surface of the OSB with heavy duty aluminum foil, to keep the moisture from migrating into the wood. (preventing warping)
I will still use the one layer of 100% cotton batting because it really helps you get things creased unlike a soft, cushiony surface. But I'll bet the foil behind it will reflect heat and keep the moisture in the cotton. At least, that's the theory.
