There's some left over from a gallon... Not enough to do another helmet, but enough for a few small things.
I always tell folks that it's not worth molding/casting a helmet unless you plan to make a lot of them or you just really want to do it for the experience. If you only want one or two it's usually cheaper to buy kits. I usually spend around $500 on a mold all totalled, including the stirrers, mixing buckets, drop cloth, gloves, etc... But I've gotten 60 - 70 helmets out of a mold with no degradation.
Speaking of gloves: It's REALLY important to read the paperwork with the silicone. For instance, latex will inhibit curing. So if you have latex gloves it can ruin your mold. Make sure to use vinyl or nitrile.
The stormy helmets were designed for vac forming so they come out great that way. Some people have done vac formed Boba helmets... It looks OK, but the details are all too soft really. Plus, if you don't already have a vac table that's WAY more expensive than the molding. My former was a few thousand to build.
I use smooth-on's 65D resin for the helmets.
Slush casting - YouTube
I don't usually cast them myself... I'm not nearly as good at it as my friend Sean. He's done a couple hundred hand slushed helmets and is a master at the craft now. They come out smoother inside than commercially rotocast products I've bought!!
