In the jewellery workshop: testing a moulding compound for resin

One thing we love at London Jewellery School is an opportunity to try out new tools and materials, so when our friends at Shesto, who produce the JewelTool range, offered the change to try out a new moulding compound we were quick to accept.

ComposiMold is a reusable moulding medium that you can melt in the microwave so we set Bronagh Miskelly, who regularly works with resin, the task of trying it out.

I have tried out reusable moulding compound before and found it fiddly requiring a sugar thermometer and a certain amount of heating and cooling before it was at the right temperature to pour. I also had trouble with achieving a smooth surface on the mould. So I was interested to try a something that claimed to be easier.

I used ComposiMold Firm which looks like a brown jelly in a tub. Melting is very simple – you work in 30 second bursts and stir the “jelly” between bursts. It only took a couple of minutes for it all to be melted and there was no mess.

I’d put the tub on an old pyrex dish to be on the safe side and even though I’d no problems I’d recommend that because I was able to rest my stirrer on it and catch any drips.

The instructions recommend using heat proof materials to contain your moulds. I used dishes from microwave meals (you can usually collect these after lunch at LJS) and coated the surface and the items I was using as blanks with petroleum jelly. Once the compound was liquid it was just a case of pouring it gently in to the moulds – I poured too quickly at first and got bubbles which I had to try to tap out, but got it smoother for the rings.

Then it was a case of letting it cool and set.

As an experiment I placed the ring blanks the same wide tray and then cut the mould down return the excess to the ComposiMold tub along with any set drips etc.

I also tested my finished moulds with resin. I found that you do need to use a thin costing of petroleum jelly of other release agent. I tested on ring with and one without. I couldn’t get the cast ring out of the uncoated mould but I was able to cut away the mould and then remelt the material and make a new one.

The moulds worked well. The rings only required a small amount of sanding so I was generally pleased with the outcome.

I haven’t done enough to tell how long one of these moulds will last or if they will tear. But I have tested reusing the compound and found it quick and easy to make more moulds. On the whole I was impressed by the ease of use and initial results.

We hope to stock ComposiMold in the LJS pop-up shop very soon.