Mold Making

Once upon a time, I sculpted a western saddle tree from apoxy and sent it off to have a mold made. That was a pretty frustrating experience, so I vowed that the next time, I would do it myself. Eventually the molds gave out - casts were warped, the molds were tearing, and it was time to call it quits. Around the same time, life started to speed up and I had to put the mold making project on hold. Several years later, I finally got it done!

The process sounds simple: nestle your master in a sulfur-free clay base, build a mold box, pour the first half, remove the clay, pour the second half and the wash, rinse, repeat to get a second mold that would have more than one tree on it. Reality was, of course, more complicated. I did some serious research first and the most helpful resources were Smooth-On and Maggie Bennett-Jenner. Maggie has an amazing monthly subscription program for micro minis and posted an amazing photo walk through of creating a resin mold for a Traditional scale sculpture on Facebook. I cannot for the life of me figure out how to get a link to that album here, but if you search for “Maggie Bennett Sculpture” on Facebook and find her album titled “Molding Kaladin,” you can see just how amazing the process is.

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I started the first mold with the mold box, which in hindsight was not ideal. Getting my hands in there to squish clay around was way too hard.

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But I managed and got all fancy with a channel and keys (the holes poked in the clay - they help the mold line up correctly later).

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Previous experience told me that I needed a way to push the inevitable air bubbles away from the tree, so I used toothpicks to add channels, including one on the top of the horn.

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First half poured! The wire is stabilizing the toothpick on the horn. I used Smooth-On Mold Max 14NV. I did research, asked around the hobby, and eventually flipped a coin between the 14NV and the 29NV.

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Apparently I neglected to photograph the clean-up process of the first half. It was…not fun. I learned that you really need to smooth that clay base! All of the clay had to be carefully cleaned off of the exposed master, or I’d end up with weird lumps on it. No one wants more clean up work. I used clay supported by a toothpick to make a sprue, and then poured my second half!

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I forgot a very important step before pouring…MOLD RELEASE. Silicone is great stuff and doesn’t stick to anything…except other silicone. Oops. All of my careful work with the keys and channel was for naught, since I had to cut my mold open.

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But I had a workable mold! Time to test. I use Amazing Casting Resin from Alumalite - it’s easily accessible and has more of a plastic-y feel than an artist resin horse. This is actually great for these saddle trees - it has more give, so if you drop your saddle on the floor the horn isn’t going to pop right off. Mixing the A and B parts for ONE saddle tree was really frustrating; it was so easy to get the proportions off and the tiniest smidgen made a huge difference. I had several frustrating pours with resin that didn’t set quite right.

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I got several good casts, though! Yay! I also learned that I really needed sprues coming off of the tree near the base of the seat, because I had a lot of air pockets in there.

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I wanted six casts to make a production mold. Here they are in various stages of clean up. In addition to the problems with the air bubbles, I decided that a cone-shaped pouring hole was not ideal; it put too much stress on the mold.

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Repeating the molding process with all six trees. I spaced them out on paper first and then used a ruler and exacto knife to etch my grid in. I decided that I’d build the mold box around the clay this time.

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With sprues, channel, and keys in place I was ready to build the mold box. I lined some scrap foam board with packing tape for a smooth surface and used hot glue to attach it to the foam board base. This probably wouldn’t work on a larger mold, but this one is so small that there isn’t really a risk of the resin being too heavy.

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I had to add clay along the sides to completely seal up the mold box, and in the process decided to abandon the channel in favor of more keys. I was careful and kept the surface of the clay MUCH smoother this time.

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It paid off! There was still some clean up to do, but there was a lot less embedded clay this time.

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I remembered the mold release this time! But not before I’d mixed a batch of silicone. Oops. I scrambled around and used drinking straws, tacked down with a bit of carefully smoothed clay, to make my pour holes. In hindsight, this is STILL a bit larger than necessary but oh well. It all worked out okay!

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Tada! The mold released worked like a charm. I pried off the toothpicks, cleaned up the clay, and gave the molds a quick wash with gentle soap to get the last bits of goop off.

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The first batch of casts! Which were all trash. It’s hard to tell from this photo, but I promise - they all had some kind of catastrophic issue. Most of them had air bubbles that obliterated a swell, and I realized that my air vent on the horn was actually allowing the resin to completely bypass the swells. Oops. I tucked a little bit of clay into the vents to slow that down and the second pour was much better - 4 out of 6 casts were functional.

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I’m so glad these are back in production! I’m offering clean casts for $8 and raw casts for $6, or $5/ea if you purchase two or more (sorry, no discount on clean casts!). Shipping in the US is $4 regardless of quantity; international buyers are welcome, just let me know where you’re at so I can calculate shipping for you. PayPal Goods & Services is the only accepted form of payment. If you’re interested in placing an order, you can drop me a line at studio@dreamflitedesign.com.