Bubbling Paint and Sealant On Props

[LittleMissRikku]

So I just wanted to touch base with someone out there as to why I have an issue with bubbles on my props.

I make my cosplay weapons out of insulation foam, use Elmer's Glue as a sealant after I've shaped and sanded and then paint with acrylics.

Has anyone else had this problem? The only factor I can think of is heat. These two props were exposed to some warm rooms and now look like the images below, whereas the hobby horse I made nearly a year ago has no signs of bubbling whatsoever but I didn't change my process. Thoughts? Suggestions? Thank you (and it only looks like the smoothest surfaces bubbles. wth?).

 

[robstyle]

have you used a needle to pop it to see if its an air pocket?

 

[Elfenstahl]

According to the FAQ of Elmer's homepage, bubbles can appear. This is refered to paper mache, but I guess it also fits craft foam:

"Papers may stretch or bubble up initially, so smooth out air from bubbles with finger and then go over area again with foam brush. Minor wrinkling will shrink and flatten as it dries. Let thoroughly dry over night and then spray surface with matte sealer."