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Silver and Gold casting porosity


Hi Daniel and Sheitanis -(I will try to answer both),

To Daniel: Thank you for your reply but I have no casting
problems(this subject “silver casting porosity” was posted by Canan
Onural). For “no casting problems” understand that the problems are
under control. I agree with you about the quality of wax and
investment. It must be high quality. about the burn cicle and
temperature I use similar to your sugestion from your friend.

To Sheitanis and Daniel: I’m not a master of anything and I don’t
intent do tell anybody what to do. I just have(after years of errors)
a good casting with low price and low technology machines. And I think
that many people are looking for it. This is what I do to cast 18k
Gold in a torch and centrifugal casting machine. #1 - Use only high
quality wax - Kerr, Hobben, Castaldo - I use Castaldo red.(It depends
on the pieces you intent to cast) #2 - Use only high quality
investment - Kerr, Hobben, Ransom&Randolph, Magic(German) -I use R&R
or Hobben(the best) #3 - Use premium alloys - I use Pandora from
Italy(for silver, Y gold and specially for white gold(nickel alloy)).
#4 - Have a good tree. conic main sprue and a lot of small sprues
everywhere. The piece to be cast must be well feed. #5 - For
centrifugal casting don’t use large flasks. I use 3"x5" stainless
steel flask. #6 - I use a “Saint Louis” Investment vaccum mixer to
fill the flasks. After fill leave the flask rest for a minimum 2
hours. #7 - The flask should be dewaxed in a steam dewaxer for 2
hours. #8 - The burn cicle: (1)diretctly from the steam dewaxer the
falsk must stay for 2 hours at 180�C. (2)go from180�C to 730�C in a 5
hours ramp. (3)stay at 730�C for 4 hours. (4) go down to 580�C in 2
hours. (5)wait at 580�C(for Yellow Gold) or 620�C(for white Gold) or
530�C(for sterling silver) before casting. When the oven is at 730�C
invert the flask for a few minutes to leave the wax gases go out. #9 -
Do the casting. And never take the torch off the metal after start
to heat it. #10 - Wait 10 to 15 minutes to pour the hot flask in warm
water(50 to 70�C). to prevent termal shock(specially with white gold).

I believe that Sheitanis’s problems are with the wax. You are not
probably doing a correct dewaxing. A small piece of wax could become
an Oxide and then hole during the casting. If the metal(and the
flask) is too hot you will have a contraction porosity that is worst
than hole porosity.

Hope this help anybody,

Christo Kiffer from Brasil