rubber molds in the summer heat

So I really didn't document the first part of my mold making process, mostly due to the fact that I had one hand sunk in dental grade alginate. It's hard to maneuver a camera when you have a box attached to you. Ha! That sentence sounded horrible.

But I'm so glad I wrote that entry, because luckily, my college studio-mate pointed out that rubber was a suitable mold to cast resin in, not plaster. So it was back to the drawing board! I had to revise my two-part plaster mold into a two-part rubber mold. Slightly more complicated, but hey... I love mold making, so the challenge was accepted.

So back to Blick I went on Friday, and picked up Smooth-On Rebound 25 rubber and plastalina . But before I could strap on my gloves and mix the rubber, I had to do a little thinking... was I going to just paint the rubber on when the plaster hand was free standing? Or should I work a little more on my prep and make a pour-able mold? The pour-able mold won out by a landslide. Yes, it's a ton more prep-work and there is a slight risk that your mold will bust a leak and rubber will go spewing out all over the place... but the results and the stability of the mold would be worth it. What can I say. I'm a rebel risk taker. Not.

the mold, plastalina and aluminum with keys

On Saturday, I built up a bed of plastalina (it's an oil based clay that doesn't dry or shrink) to rest the hand on in a horizontal position. The one benefit of working with plastalina on a 90+ degree day is that it gets super pliable and soft with the heat. Then I used some aluminum flashing to make a quick and easy flex mold. It's so much easier than cutting and clamping wood together, fo realz. I used the plastalina to fill in the gaps, and to mask the bottom 50% of the plaster hand. Then, I pressed a couple marbles into the clay, and made some indentations to make keys. Keys are super important, because they will ensure that the mold aligns properly when you're ready to cast. Sounds easy, but that prep work literally took me five hours.

I sprayed the mold quickly with Ease Release so that the rubber wouldn't adhere to the plaster hand. Then it was all measuing, mixing and pouring from there! The Rebound 25 is a great 1A:1B ratio, so it takes the guesswork out of measuring. The first part of the mold came out better than I expected, so Saturday was a win in my book!

pour #1 after it had set for 12 hrs. ready to de-mold!

top left: before removing plastalina. top right: after. bottom: rubber with keys clearly a success!

On Sunday, I completed the second pour of rubber. I basically did the same steps all over again... built up a bed of plastalina, secured the aluminum flex mold, mix, pour, wait. When the rubber had set, I stood the hand/rubber mold up. I noticed that all of the plaster on the base of the hand wasn't covered, so I decided to mix a small batch of rubber and cover it up. Totally worth it in my books. I'll add some pics of that with my next post.

Today I'm hoping to make the first 1/2 of the plaster mother mold. Wish me luck!