Much progress on the urethane front, all of it good.
Here's the stuff coming out of the scale mold. Recall that the first layer was airbrushed in, then I used a chip brush to glob in a second layer.
Very good results! I wish I had added pigment to that layer I airbrushed in, but that's cool. The goal was to simply see if the stuff could be airbrushed, which indeed it can. I'm really happy with the results. I think the mermaid tail project is going to turn out really nicely, if I can continue to get results like this. It's also very cool that I can airbrush the stuff, as that means I can do different coats in different colors, creating a really cool effect without painting it.
Here is how the diamond pattern looks. Same thing as above, the first layer was airbrushed, the second was chip brushed in. Again, very satisfactory result. The real take-away from this round is that in order to use a rigid mold, you need to put down a coat of mold release. It did not at all effect the quality of the pull. I'm pretty stoked about this. It basically means that this urethane can be used successfully on both rigid molds and flexible ones.
With those test behind me, and a few lessons learned, I moved on to the next round. This time, I added some So-Strong pigment to the urethane, and used a chip brush to put it into the mold. I also backed it with some fabric. I'll post the results of this round once I have them.