Anyone ever try using cornstarch as a mold for short runs??
I know that it is used in the candy industry for things like gummi worms…
Villy
You mean as a mold RELEASE, or as the mold itself, like a sand casting? As a release, it’s too coarse, and most suggest talc. As a mold, I’ve never seen anything about sand casting with resin. I suppose it’s worth a shot, but I’d use modeling clay instead as it’s non porus.
Not an expert so I’m not sure I understand “short runs”. I’ve tried using corn starch and IMHO it would be doable but you need to have a way to compress the starch while at the same time pressing in the master of what you’re trying to mold.
I tried this using a small wood box, 1 inch marble, “watered down caulk” (mixture of clear caulk, water, and glycerine).
I put about 2 inchs of corn starch in the box, compressed it with another piece of wood that was sized to just fit in the box, but every time I’d press in the marble, it would pretty much destroy the starch (cracking around the edge, cracking where I’d press in the marble, etc).
This would always result in a less than round half moon. I was only goofing around in my tests so they were not “scientific” but I do think it is doable.
Corn starch is used as a mold for about every gummy candy you eat, from “Dots” to gummy worms, to those orange slices you’re grandma would give you (take no offense old timers 
).
IMHO you could size a wood box from a plaster casting you made, press the corn starch down using the plaster casting, use the liquidfied caulk I mentioned, and could get some ok results. The starch is very fine, seemingly near “ash” consistancy, even tho my “marble” was far from perfect, where it did take, it was pretty smooth.
Just my 2cps