Tonight I mixed up a small batch of urethane to do some tests on my new rigid mold.
One part I treated with mold release, one part I treated with baby powder, and another part is left untreated.
I had some leftovers, so I also did some tests on the cape mold. I added some mineral spirits to the urethane to thin it out, just to see if that would have any effect.
Though not fully cured as of this writing, ALL Of the urethane samples ended up "pulling back" from the materials. Be it 1630 or silicone. This is not good news. BUT what is good news is that regular latex rubber worked AMAZINGLY well on the 1630. Flawless. Makes me think that the way to go is to pull a rigid mold of the cape. That will be a lot of work, and a bunch of expense, BUT it will significantly speed up the process of making a cape, and will make for better results that are less error prone. There's good motivation to make a rigid master, though it will LITERALLY cost me a few hundred bucks in materials. And also be entirely unweildy. We shall see.
But based on my experiments, I am thinking that I may do the boots in Latex instead of urethane as I had original suggested. I wonder how stone would work?