I get lots of questions about using molds, not designed for resin, including casting resin in a soap mold. Sometimes non-traditional molds work, sometimes they don’t. In cleaning up my studio this week, I found a plastic soap mold. It was at that point that I thought to myself, “How a big a disaster can casting resin in this be?”
Oh, you won’t be disappointed.
Note: My resin was a bit cold in the day I mixed it. The two parts didn’t want to blend and I had to mix it more forcefully than normal. This introduced more bubbles. It reminded me to make sure my resin is warm before mixing to minimize bubbles in the resin.
I also decided not to add anything to this resin. I wanted to be sure that if this didn’t work, the resin was the only factor. I didn’t want the results to be clouded by pigments used, inclusions placed, etc.
Before pouring the resin into the mold, I sprayed it with a couple of light layers of the Petrolease non silicone mold release. This is my go-to mold release when I anticipate difficult demolding situations. I used it when I cast resin into a gelatin mold and I’m convinced it was the magic bullet to help me get out those castings.
While you see 3 ounces as the capacity for this mold, I only poured in an ounce and a half of resin. Why? First, this mold would produce a much deeper casting that I would ever want to use as a resin embellishment. Second, I wanted to make demolding difficult. If it’s too easy, I won’t have learned much.
Once I finished the pour and removed the bubbles with a heat gun, I covered it with a dome and let it cure for 24 hours before demolding.
The simple ‘twist and push from the back’ didn’t budge the cured casting. I had to pull the mold away from the side of the resin.
Note: If you haven’t used soap mold, the plastic is quite thin. I would say it is very similar in thickness and flexibility to a plastic, take-out food container.
With molds designed for resin casting, once you have a loose edge, you can usually pull up on the edge to lift the resin out of the mold. Doing that in this case completely destroyed the mold.
And here is my finished casting. While the resin cured fine, I was unable to demold it from the plastic soap mold. In fact, most of the star is adhered to the resin. I was not able to get it off.
What have you cast resin into that you were unable to demold?