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Lab talk, the good, the bad, and the ugly
Metal
Looking for advice about casting fundamentals
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<blockquote data-quote="CatamountRob" data-source="post: 340802" data-attributes="member: 660"><p>I use propane and oxygen, you can cast with acetylene but it’s much dirtier. I’ve never had access to natural gas but it works fine, maybe requires a different torch?</p><p></p><p>I cast gold crowns with a direct ball reservoir sprue. You want the ball in the center of the ring, the top of the crown less than 1/4” from the top. No sharp corners, the ball needs to be bigger in cross section than the largest part of the object your casting. I burnout full gold at 1300 F but let it cool to below 1000 before I cast it.</p><p></p><p>I cast copings for PFM’s on runner bars in oval rings, again, no sharp corners and keep them angled back relative to the direction of spin. I burnout those rings at 1400 F, I preheat the alloy and crucible in the burnout furnace with the rings.</p><p></p><p>If you are casting high palladium alloys be careful with the 02, if the torch is really hissing it’s probably set too high. Palladium has an affinity for oxygen.</p><p></p><p>Post a few pictures of your sprued crowns or copings, it would definitely help.</p></blockquote><p></p>
[QUOTE="CatamountRob, post: 340802, member: 660"] I use propane and oxygen, you can cast with acetylene but it’s much dirtier. I’ve never had access to natural gas but it works fine, maybe requires a different torch? I cast gold crowns with a direct ball reservoir sprue. You want the ball in the center of the ring, the top of the crown less than 1/4” from the top. No sharp corners, the ball needs to be bigger in cross section than the largest part of the object your casting. I burnout full gold at 1300 F but let it cool to below 1000 before I cast it. I cast copings for PFM’s on runner bars in oval rings, again, no sharp corners and keep them angled back relative to the direction of spin. I burnout those rings at 1400 F, I preheat the alloy and crucible in the burnout furnace with the rings. If you are casting high palladium alloys be careful with the 02, if the torch is really hissing it’s probably set too high. Palladium has an affinity for oxygen. Post a few pictures of your sprued crowns or copings, it would definitely help. [/QUOTE]
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Lab talk, the good, the bad, and the ugly
Metal
Looking for advice about casting fundamentals
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