u/Apart-Sherbet-6923

I recently started making glidebaits from polyeurathayne and microspheres after doing well with my wooden ones. the one issue I can’t seem to overcome is that the inside of the resin always has bubbles- like a sponge. I’ve experimented with different procedures and different quantities of microshpere- all seem to lead to the same result. the surface of the lure is smooth but when I need to sand to remove imperctions the inside is like a sponge. right now I’ve been mixing the microspheres into part a before incorporating part b and casting into silicone moulds I made myself.

does anyone know what I can do differently? is this normal? can I do something post casting to fix it?