by Mike - Alumilite » Tue Jan 20, 2015 10:35 am
Larry is right ... try pouring the mold half way or however far necessary and then rotate the mold to allow the trapped air to escape by tilting the mold. Once you believe the air has escaped, continue pouring. The other option is to pour half way, then "burp" the mold. Basically squeeze it right below the point where the air gets trapped. This changes the angle of the undercut and normally flushes the air bubbles out and when you release the mold the resin sucks back into the undercut filling it. After burping the mold a few times (from the bottom or below the under cut), simply continue to pour your mold until full.
Alumifoam will do better but that air still needs somewhere to go. So you may decrease the size of the air pocket however I think it would still be a problem area for you as that air has no where to go.
Mike