After studying the archives on the need for a sealer for EPS, I have this question. If you are willing to fine sand (say 150 to 180) an EPS blank, is it still advisable to seal it with spackle? I get a pretty smooth surface after 180. I’m thinking that you’ve eliminated most of the pores in EPS that way and could end up with better adhesion (not using spackle), and less yellowing. Do you think it would still soak up too much resin without using spackle?
If you get a pretty nice and smooth surface with a 150 grit, I wouldn’t bother to spackle. It depends alot on the EPS though. Last board I did I used a slightly heavier density of foam than previously, only sanded to 80 grit, no spackle. Used Greg’s Loehr’s formulas for resin to board length and still had a fair amount of resin on the floor. If you want to test it, find a few pieces EPS, roughsand one, fine sand another, lam. I guess you could messure how much resin you actually use, but also if you put some color in the resin, you can see how far into the foam the resin soaks. For the lightest foam I’ve see color around the EPS beads as far as a few centimeter into the foam. regards, Håvard
thx. I will do a test. Are you just sanding to 80 grit? It just seems rough to me at that grit, but I have no basis for saying that.
I’ve tried sanding it to a finer grit, but I always ended up ripping out some foam beads when I got close to smooth. No good. I don’t think I can ever get as smooth a surface on an EPS blank as on a PU blank. I’m not going to airbrush the foam anyway. I’m using resin tints or opaques to cover the flaws of the EPS and I’m just building boards for my self, so 80 grit is just fine with me. regards, Håvard