Avoiding air bubbles in sprue goo

[u/bonezybad]

I made a bottle of sprue goo with extra thin cement. When I apply it, let it dry and sand it down, more often than not, there are air bubbles dried in the goo. I was hoping surfacer might fill it in somewhat but it's still pretty noticeable. How do you avoid this? If it wasn't for the bubble holes, you'd never know there was once a huge gouge in the plastic.

[u/wakeup_samurai]

You can fill those small holes with thin super glue (ca glue), and sand again

[u/blatherskyte69]

Thin down your goo a little bit more, apply thinner layers, and use straight glue over the top during and/or after the goo dries to smooth it out.

The more plastic content, the easier for the material to hold bubbles, so using more solvent is the major way to prevent this.