Casting Spikes, Something Clever (day 17)

“Day 16” didn’t amount to much – motivation was low and I didn’t have a clear idea of what I wanted to accomplish. I spent a bit of time carving and refining the new putty work on the pauldron. Tonight I opened up the spike mold I made a couple days ago to see how it turned out, and cast a few copies of the pauldron spike.


I continue to have trouble with my mold rubber. Over 48 hours after pouring the rubber and it is still tacky to the touch. Touching the surface of the mold I even left fingerprints in the surface. And when I took apart the lego box around the mold rubber, areas where the mold rubber formed a thin layer on the lego bricks, the rubber stuck to the lego brick and tore off from the rest of the mold. This mold rubber should not perform this way, normally it’s very strong and resilient when cured.

I don’t know what’s going wrong with the mold rubber. I may just need to buy a fresh batch. But I’ve not known this product to misbehave like this. When it’s too old, it’s too viscous which makes it hard to pour effectively, but it still cures properly, so I don’t know what’s going wrong. I spent a solid 4 minutes shaking the container of mold rubber catalyst. Perhaps I need to increase the amount of catalyst I’m using, or check my measuring/mixing process to make sure I’m not inadvertently reducing the amount of catalyst I’m mixing in.
From there I cast a few spikes. Because of the way this mold is set up it’s hard to avoid bubbles in the mold – I have to be a bit aggressive about getting air bubbles out before the resin cures. I cast three spikes, and the castings got progressively better each time: The first had a massive bubble covering about half of the spike’s base, the second has a smaller bubble, and the third is free of any major bubbles. I can fill these with epoxy putty or something to correct the parts, but I may just cast them again instead.

It’s kind of another low-yield day on the project, but progress is progress. Also, tautology.