Back to Ganoksin | FAQ | Contact

Building a complex piece around modeling clay

A short video appeared on my news feed in the middle of a sleepless night. It showed a very complicated gold piece with many forged and formed elements being built up around what appeared to be gray modeling clay. Once completed, plaster or casting investment was poured over what would be the back of the piece. Once the plaster or investment dured, the clay was somehow removed and the pieces soldered while being held in place by the plaster or investment. I have seen something like this before and may even have commented on it. If that is the case, I apoligize for repeating myself. The surrounding of the video looked to be a very primative shop. Can anyone tell me what this process is called.? Other than that, my technical questions are: How do you remove all the clay? And, can you solder while pieces are held together with plaster or investment. Hopefully this was not a sleepless abberation. At my age they happen often. Thanks for any help…Rob

1 Like

Not sure about the clay, but soldering while pieces are held in place with investment has a long history. In fact Ransom & Randolf —investment manufacturers (Ultravest) -used to make a Soldering Investment just for that purpose. I used to use it to hold wires onto study models to make removable orthodontic appliances.

There have been times where I’ve arranged and then embedded elements—prong heads for example—in wax, poured plaster/investment around them and then once set, melted the wax out. You need a counterintuitive hot and hissy flame to get the job done (especially with conductive metals like silver) but it works great.

1 Like

I did that once, having several heads to solder together. I embedded their backs in plasticine in a small box and poured investment on top so the prongs were covered and held in place. When it dried I peeled off the plasticine, leaving the prongs embedded in the investment and the bases exposed for soldering.

1 Like

Exactly! What she said.

Please excuse any typos-- curse my clumsy digits…

Thanks for the replys. I remember now that the last time I asked about this I looked for small amounts of investment to buy and couldn’t find it. I don’t do any lost wax casting, so I don’t have it on hand…Rob

You could try regular plaster of paris. Silver soldering shouldn’t get the plaster hot enough for long enough to make it break down. You could also try gypsum cement, sold under the trade name “Hydrocal,” which is stronger than plaster of paris. But it may also be more difficult to break apart to get the piece out.

a similar method is used to make filigree components: form your wires, stick on something sticky (like plasticene, pour investment over, dry, turn upside down, remove clay, solder all the little joints in one go

Just a thought, In sculpture classes we used a mix of plaster of paris and clean sand. Held up to burnout and casting.


That’s not how I make filigree, but I suppose that it could be, if necessary…Rob


I haven’t seen Rio Grande’s Soldering Clay mentioned yet. It’s item number 504093 and sounds like what you’re calling investment for soldering. The description recommends putting your elements in wax or water-based clay, but since I have no idea what water-based clay is (a search kept turning up air-dry clay and I have no idea if that’s the same stuff… also something called LED that apparently was developed by Disney), I did a chat with someone at Rio and he said plasticine should work fine, just don’t get it into the joint itself (which, yeah).

Please note that I’ve had some for a while but haven’t used it yet and was thinking about needing to when this topic showed up.

It’s a powder and comes in a one pound jar. From one of the pictures, it looks like it’s a re-brand of an older product called Soldering Investment that came in a 5lb. box.



It’s an Indian filigree technique, the clay is plasticine and plain plaster of Paris works but can crack so I add some silica sand or some chopped up fibreglass scraps (there’s a surfboard manufacturer near the studio I go to who doesn’t mind us dumpster diving for off cuts) to reinforce it. Look up GoldsmithJack on YouTube for some real experts making 24k gold Indian jewellery using this technique.