I wasn't sure which forum to put this under, but here goes. I've used the acid free hard foam board for displays before, but would 100% polyester like the replacement pads sold for lawn furniture be safe? I'm looking for something to use for a case to display several small knives in. Something like the cases that squeeze the knives between the glass and foam, but I want to make sure my padding won't damage my blades or handles. I know the polyurethane foam is a no-no, but thought the polyester might be safe.