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Casting trouble


#1

I am having some trouble with lost wax casting. I am fairly new to
this and have had some great successes and some puzzling results.
Tonight I casted two flasks and both had major problems. One bracelet
had many pit marks and what looked like large deposition of
investment on several places. The other was a beautiful piece except
towards the end of one side of the bracelet the silver looked like
it had blown out. It blew out onto other pieces I had sprued in the
same flask. The funny thing is it blew out i n one place, but the
silver flowed right to the end (and there was no problem with spruing
on that piece.

The bracelets were made using 12g sheet wax, with some red modelers
wax on the second one. I use an acetylene torch with sterling silver.
The silver flows without a problem.

Thanks for any ideas on this.
Jan Plotkin
Davis, Ca.


#2

Probably to wet in the investment stage… the excess water will
crack the mold interior as it is heated. Water has a way of finding
it’s way out when the outer shell gets hot and the only escape is
the sprue!

Ringman


#3

HI Jan

Problem number one sounds like you maybe didn’t mix the investment
long enough. Are you using an electric mixer? You can get a cheap
one and mix much more thorough than by hand. Also, are you vacuuming
the flask?

As far as the blow out goes-- It happens because the investment
breaks inside the flask. Did you mishandle the flask? Drop it? Bump
it? It could aslo be that the two pcs you had sprued up were too
close to each other. When spruing up flat pcs, try to put them so the
are NOT parallel to each other. Makes the walls of investment a
whole lot easier to break. Put them at angles to each other.

Good luck.

-Stanley Bright
Owner
A&M Jewelers
Baltimore, MD