Acrylic or polyurethane with Alumilite

[Muggsy1776]

I'm trying to cast paper and I'm getting lots of air bubbles around the edges of the paper. I suspect the pressure pot is pushing out trapped air in the paper. My thought is to seal the paper prior to casting. My question is: spray with a clear acrylic or a polyurethane? I'm using Alumilite slow which is a urethane. Any thoughts?

 

[montmill]

I've used Modge Podge.

 

[dschem]

I use printable waterproof labels and have never had an issue with bubbles, a just straight cast into alumalite. What pressure are you casting at?