Common mistakes in cupellation - Gold Refining Metal Extraction Forum Since we cupel 84 samples at a time, it is impractical to load the lead buttons in to the cupels while they are in the furnace We place the buttons into the pre heated cupels then load that to the furnace Once our Mag-oxide cupels are pre heated, they turn from a grey color to a brilliant white De-slagging was mentioned and is also very
Cupel sizes - Gold Refining Metal Extraction Forum Pre heat your cupel to at least 700F for at least 15 minutes Probably moisture trapped inside which can't escape, once the metals start to melt Lucky they didn't explode Could also be the materials used in their makeup, but usually due to being not fully cured
Chemical - Bone Ash Binder for fireing DIY cupels You want to remove the gelatin Then calcine the bones to a complete calcine ( 900 degrees C ), white hot for 1 hour, longer for larger bones Crush to all minus 100 mesh Mix with 10% cement, just enough water to get the material to bind, press to desired shape and size Most mints required the cupel to dry dry for 2 years before use
Cupel sizes | Page 2 | Gold Refining Metal Extraction Forum To cupel properly, you need 2 components for the reaction to happen properly The first is temperature, 1850 F , the second is a bit of atmospheric Oxygen The conversion of Pb (Lead), to Pb oxide Metallic Pb will not absorb into the cupel, only PbO will absorb into the cupel, bringing other base metal oxides as well
Questions about cupellation - Gold Refining Metal Extraction Forum The cupel composition can make a big difference The types can vary as to the lead retention and potential losses All in all, I think bone ash cupels are generally the best, but they are more expensive, less durable - they can break easily if handled roughly or if you don't store them properly in a dry area
How hot does a cupel furnace need to be? Can it get hot enough that PMs . . . The lead oxidizes base metals into a slag and when the volume of the lead after it is driven by oxidation is about half, the remaining lead and slag is poured into a assay cone mold, deslagged, and that lead alloy chunk is cupelled in a bone ash cupel
Chemical Bone Ash Binder for fireing DIY cupels - Gold Refining Metal . . . I was just looking at his torch assay book and I found the cupel mold that I bought from him many years ago (before he passed away) His recipe for cupels uses: 8 tablespoons of BONE ASH 1 teaspoon of WHITE FOUR This mixture is dampened using a mixture of: 1 2 pint of WATER 1 tablespoon of Elmer's all-purpose white glue 2 tablespoons of WHITE
Trying to cupel - Gold Refining Metal Extraction Forum Scotifications are not done in a cupel, usually for assays it is a melting dish which, unlike a cupel will not absorb the lead The borax is most effective if it is anhydrous borax All borax is borax but anhydrous has been heated to drive off the water 20 mule team borax has 10 waters and there is also a lot of 5 waters borax out there
melting in cupel - Gold Refining Metal Extraction Forum Base metals will contaminate the cupel quickly as the are designed to absorb base metals in assays No need to 'baby' then like the dish, but a gentle preheat is still recommended to prevent any trapped water from causing a steam explosion and chipping the cupel This preheating can be accomplished at the same time the cupel is glazed with borax
Pre heating the cupel - Gold Refining Metal Extraction Forum Thank you I am keeping the cupel on top of the furnace before preheating and and then preheat them, until red After loading the button, allow them to settle for 4 min, and let the "blower in" for next 10 min Then for next 4 min allow the "blower out", and give 10 more min, switching off the furnace, to reduce the temp up to 965 degree C