[TheForge] "sculpting clay"

[James Binnion]

On Friday, September 19, 2003, at 12:31 PM, Jerry Frost wrote:

> Unfortunately I deleted the original message unintentionally. As I 
> recall
> there was a second part to the question. If I recall correctly the 
> question
> was relating to using modeling clay for making originals for investment
> casting.
>
> If I'm correct there's a real problem with adequate burnout of modeling
> clay, basically it leaves residue that can't be removed and plays hob 
> with
> castings.
>
> Frosty
>
In traditional sculpture work the original model is often plastilina 
and then a mold is made of it with a liquid rubber. After removing the 
the mold from the clay master the mold is filled with wax and a wax 
pattern is cast from it. That wax pattern is then invested and cast 
into metal. There are "clays" that are supposed to be similar to 
plastilina that can be directly burned out in the casting process but I 
have never used them and the few people who I know who have did not 
like them. It is also possible to work on the original directly in wax. 
The favorite is a "Victory Brown" micro-crystalline wax that is fairly 
pliable at "room" temperature. But it has a fairly limited working 
range if it is too warm it is very soft and will need a wire  armature 
to help hold its shape and that will preclude you from burning it out. 
Or if it is too cold it will be too hard to easily work with. So it 
works best in a well controlled environment.

Jim