Cast gold in RTV Mold?

[Yeah Right]

Can you Cast gold in an RTV Mold?
More than once?
Thanx

[Lawrence Gould]

Why not make a wax from the mold and do it properly ??

"Yeah Right" <midgaar...@earthlink.net> wrote in message
news:rff0bt43kb7qamcat...@4ax.com...

[Don Norris]

I meant to answer this question when it was asked and could not find the
location of the photos. This question was asked once on one of my list.
I usually try to take photos to go with the answers on that list, but
could not find them. The question was: "Can you pour gold in to rubber
molds?" There are several reasons that you can pour gold in to rubber
molds. The first and most important is that they can not withstand the
high melting temperatures of gold, silver, brass, or any metal that
melts over 700 degrees. They will simply burn the mold rubber. I found
where I posted the photos on one of satellite sites that I make myself,
so that I do not have to bother my web master. You can find them at:
http://Silvercasting.homestead.com/moldsmetal.html

The second reason gold (or any high melting temperature metals) can not
be just poured in to the rubber mold is that they freeze so fast. As the
metal makes contact with surface of the mold it cools the metal and it
solidifies (freezes). Then the solidified metal plugs the sprue. This
prevents the mold from filling.

The third reason is that all metals need something to force the metal
into a mold. Some force to push the metal into mold and
completely fill it. Simply pouring metal into a mold is just
using gravity. With small amounts of metal, gravity is not enough
to force the metal in to the mold. It is not enough force on
the small mass to replace the air that is
trapped in the mold.

I have cast pewter ( lead free American Fine Pewter) directly in to
vulcanized and RTV rubber molds. It melts around 450-500 degrees and I
pour it around 600 to 650 degrees. It also remains molten for a long
period of time, and is less affected by the cooling by the surface of
the mold. However, gravity is still not a very strong force to use to
cast anything. The metal just can not run down into the mold and replace
the air and will result in an incomplete cast. This could be prevented
my making a
large reservoir in the mold, or a second mold taped above it,
to hold more pewter. The gravity on the extra pewter
would add the necessary weight to fill the mold.

Usually this question comes up because someone want to cast pieces, but
does not want to invest in casting equipment. I understand this
completely. I teach casting to many, many students every year. For most
it would be silly to invest $1,000.00 to $2,000.00 in equipment. To make
a wax and cast it, is not always an alternative for most beginners, or
even accomplished silversmiths that simply do not do much casting. For
most people this would include the cost of a kiln for burn out, and a
caster (vacuum or broken arm).

Steam Casting can be the answer to your question!

If you have a rubber mold you can make a wax pattern, make an investment
mold with it, burn the wax pattern up and cast it (lost wax casting). If
you do not have a wax injector (again, you can not just pour wax into a
mold, relying only on gravity) you can use either a glass, plastic or
metal turkey baster. Simply melt some wax in a double boiler ( for
safety), suck up some wax in the baster, and squirt the wax into the
mold. Then you can invest the wax, burn it out and steam cast it. The
cost of the homemade equipment for steam casting is less than $50.00.
For most people this home made equipment will cast all you need. At
least it will cast enough to pay for a kiln and caster!

I have decided to offer a free, with no obligations, Online Steam
Casting Class. This will be a 6 to 10 week class for any one that would
like to start casting silver, gold, and pewter on limited budget. The
cost of tools, supplies and equipment for this class will not cost more
than $50.00. Even less for most, because they will have some of the
necessary materials. We will begin the class in about two weeks. If you
have an interest in this free online class just e-mail me at
dno...@frii.com.

Don Norris
http://www.frii.com/~dnorris
http://silversmithing.homestead.com/SilverClasses1.html

[Yeah Right]

I think I downloaded a text on steam casting a while back, I'll give it a go
when time permits. Thank you.