Resin Casting: One-piece cut molds

One-piece silicone cut molds are a relatively easy way to cast miniatures in resin.

Six years ago we ventured into the world of resin casting to make copies of some of our conversions. It took a lot of trial and error to get something that worked consistently, but we found making a pressure pot was essential. All of the molds we created over the years were two piece molds, which are quite labor intensive. After watching a few YouTube videos by Miscast, where he talks about some of the imaginative models he converted and cast, I started to think about the prospect of creating molds again. What interested me most was trying to make single-piece cut molds, like Miscast favors. These are molds where you pour the silicone all at one time, creating a solid block of silicone surrounding the model. You then use a blade to cut the original model out of the silicone, taking care to cut it just enough to release the model and remain as a single piece. Robert Tolone has some excellent YouTube videos about the process that I encourage you to watch if you are interested. In one of his videos, he used one-piece cut molds to cast some characters from the excellent board game Root. In it, he attaches the models to small plastic cups and pours the silicone into them. This seemed like a relatively straightforward process, so I decided to give it a try, making molds of some old metal Games Workshop models I hope to use as a basis for conversions in the future!

Thorn Moons Crusade: Making a mold for the Defenders of the 73rd Moon

It's understood, we'll do or die.

A few weeks ago, we showed our progress on our remnants of the Imperial Army defending the Thorn Moons. Since then, I have disassembled all of the models and built a few more weapons and sculpted some arms, preparing to create a silicone mold. I am pleased to say that I made the first mold for the guard, and it was quite successful! I wanted to show you a few pictures of the resulting mold and the resin casts it produces.

Ways to improve resin casting: pressure and vacuum chambers

Using a pressure chamber dramatically improved my resin casting.

Getting into resin casting can be a difficult thing, with so many details to consider (what silcone and resin to use, how to create effective vents, etc.), that it is easy to get overwhelmed. I found one of the trickiest elements was determining how pressure and vacuum chambers can be used to improve the process. Both are used to reduce bubbles in the final product, but since they work in very different ways, each is suitable for a different aspect of the process. A vacuum chamber is used to physically remove bubbles from a material (and all the air from the chamber itself) by creating a vacuum, while a pressure chamber shrinks any bubbles present in the material via pressure. Because the mixing process of silicone introduces air bubbles into it, a vacuum is applied to the mixture before using it (pouring it) to create a mold. This is possible due to the slow curing time of most silicone (~5 hrs). Resin, however, solidifies much more quickly (~15 min.), making a vacuum not a viable way for removing the bubbles in resin before injecting it into the mold. Instead, the mold is placed in a pressure chamber after the resin is added, to shrink any bubble to a negligible size. Although using both strategies are not absolutely necessary for creating molds and using them for casting, from experience, it dramatically improves the final product. I currently use both, and they allowed me to nicely cast the true-scale Space Marine that I recently built. In this post, I wanted to talk about both vacuum chambers and pressure chambers, and how they were important for dramatically improving my resin casting abilities.

Making a two part mold: Casting resin models

I venture into creating silicone molds...

Having spent the better part of two months working on sculpting a true-scale Space Marine, it became clear that I could not continue to resculpt power armor each time that I wanted to make a new true-scale marine. I decided that the surest solution would be to make a rubber mold to cast additional copies of the armor. Although the process of making a silicone mold and using it to create resin casts is relatively straightforward, it was something that I had absolutely no knowledge about, so I was quite apprehensive about it all. After watching a YouTube video or two about the process, I decided I would give it a go, and ordered a starter kit from Smooth-On. Now that I have made my first mold, I wanted to share some of the things that I learned from the experience to hopefully encourage others to start creating molds to cast custom-made or sculpted components.