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Mold Mixes information please!
Posted: Fri Mar 19, 2004 12:36 pm
by froggee501
I'd like to try doing some (successful) glass castings... I am definately looking at doing this long term, and would like to do this right.
At this point in time, I'm looking at doing some fairly detailed lost wax creations for jewelry. I assume this means that I'm looking for a mold mix of a very fine grain. And would I want to use a debubblizer, like I do for metal castings? Eventually I'll probably try to branch out into larger open back things, but I have a very small kiln, so I'm happy to stick with the smaller things for now.
Basically, I'm looking for recommendations... What mold mixes do you recommend for me and why? What are other mold mixes and what are they good for? If this turns into a general information thread on mold mixes, that's just fine by me
I tried searching and looking around, but only found information on the process, and not the products.
Emma Tucker
Posted: Fri Mar 19, 2004 10:48 pm
by charlie holden
Most people start with 50/50 plaster and silica by weight. There are a million variations and alternatives from there. Check the old archives and search on plaster.
I suggest the book "Pate de Verre and Kiln Casting of Glass" by Jim Kervin and Dan Fenton. It lays out all the basics and offers a way of thinking about mixes in terms of binders, refractories and modifiers, which is very useful. It is a little out of date but I'm surprised every time I go back to it to find something I hadn't noticed before. Their recipes are quite basic. But if you are willing to experiment they mention lots of alternative materials.
ch
Posted: Fri Mar 19, 2004 11:08 pm
by froggee501
I'm assuming though that not all plaster is created equal... what sort of plaster? and where would I get silica?
And for my personal use, right now, I'd prefer something that's already mixed, where all I have to do is mix it with water... Something I can buy ready like that.
Posted: Sat Mar 20, 2004 12:30 am
by Helen Stokes
Hi Emma, I would suggest you use dental plaster (with silica flour 200)as it is finer than potters plaster and it sets faster, it gives a good finish on the glass and is easily removed from the glass after firing. I hand build my moulds so setting faster is good for me. I mix the dental plaster and silica dry and then add it to the water, there is very little effort in mixing the dry ingredients. Measure equal quantities by volume into a bucket with a lid, make a small hole in the centre of the lid and put a paint mixer attached to a cordless drill through the hole and the dry ingredients can be mixed reasonably free of dust.
Posted: Sat Mar 20, 2004 7:58 pm
by charlie holden
froggee501 wrote:I'm assuming though that not all plaster is created equal... what sort of plaster? and where would I get silica?
And for my personal use, right now, I'd prefer something that's already mixed, where all I have to do is mix it with water... Something I can buy ready like that.
Dental plaster is stronger than pottery plaster. But if you are making jewelry strength isn't really much of a concern, since the glass won't weigh much. I like a plaster to take a while to set since I am a plodder.
There are some premixed casting plasters but I have never used any of them. One is called Castalot and is pretty hard -- made for repeated firings of open faced molds. Another company is Ransom and Randolf. You should contact some of the retailers linked at the top of the page and ask them.
ch