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Want to sculpt a clay mold that I can then make a fiber mold over and slump/drape over that. Does anyone have advice as to what kind of clay and how to prepare it for the fiber mold?

I've use model clay that doesn't dry - so you can use it over again. Then obtain fiber paste ready to use in a pail (I went to a wholesale refractory supplier, Smith - Sharpe in Minneapolis). This stuff is super sticky but can be placed over the clay and, once hardened, becomes a wonderful refractory mold. Can't remember if I sprayed the clay first with PAM, but I'm sure you can dig the greasy modeling clay out of a dryed fiber mold either way.

Mark Hall wrote:I've use model clay that doesn't dry - so you can use it over again. Then obtain fiber paste ready to use in a pail (I went to a wholesale refractory supplier, Smith - Sharpe in Minneapolis). This stuff is super sticky but can be placed over the clay and, once hardened, becomes a wonderful refractory mold. Can't remember if I sprayed the clay first with PAM, but I'm sure you can dig the greasy modeling clay out of a dryed fiber mold either way.

Mark
Tell me more about this paste/ refractory. Is this something I can cast glass into? What temperatures is it good for?
Ron

Under the trademark Fiberfrax, LDS Moldable. Comes premixed ready to go, has a hot face of 2300 degrees F. I got it in a 5 gallon pail.

How long will a 5 gal bucket keep?

I've got some I bought 15 years ago. It's a bit dryish, but still usable.

It has a dated shelf life which had expired (which is why I got it super cheap). It costs so much to buy that the supplier has to pay attention to the shelf life date so as not to deliver bad stock to his regular customers. It does however last much longer that the stated shelf life so they peddle it off to us craftsman.