Cupelling help

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Just an idea, is there a lot of iron in your cons. Looks like you may have excessive Iron. This happened to me when there was way too much iron in my prill from a smelt and I failed to get the smelt chemistry correct.
 
Your sample size seems to be creeping upward. This time it was 3 grams to 30 grams of lead. If anything until you can get a successful cupellation you should using progressively smaller samples not larger.

I think that by using the bits that broke off from the main chunk you may have unintentionally been using slags. I would hammer the cone shaped bar flat and drill a sample from the center after you wire brush off all of the loose bits. To start we want to assure you are starting with a lead/cons sample.

If you do a scorification as per the instructions that lead cone should be hammered free of slag and brushed off to assure most of the slags have been removed before cupellation. My only experience with scorification has been with copper based bullion not lead sulfide (galena) and it has always produced a clear green slag.
 
Just an idea, is there a lot of iron in your cons. Looks like you may have excessive Iron. This happened to me when there was way too much iron in my prill from a smelt and I failed to get the smelt chemistry correct.
There could be iron in it how do I fix this???
 
Your sample size seems to be creeping upward. This time it was 3 grams to 30 grams of lead. If anything until you can get a successful cupellation you should using progressively smaller samples not larger.

I think that by using the bits that broke off from the main chunk you may have unintentionally been using slags. I would hammer the cone shaped bar flat and drill a sample from the center after you wire brush off all of the loose bits. To start we want to assure you are starting with a lead/cons sample.

If you do a scorification as per the instructions that lead cone should be hammered free of slag and brushed off to assure most of the slags have been removed before cupellation. My only experience with scorification has been with copper based bullion not lead sulfide (galena) and it has always produced a clear green slag.
I'll buy some scarification dishes next week and try that. Thanks heaps
 
Guy's how long do it usually take for the cupel to absorb all the lead? 30min,? 1 hour? 2 hour?
 
For a typical bullion fire assay usually 45 minutes. At that point you can see the precious metal balls sitting in the depression without any lead, which has all been absorbed into the cupel.
 
If I’m not mistaken the remperature should be higher, try 1050C
Did you buy ir make the coupel dish.
The temperature should be around 800 - 860 C. max for Au. The black scum on top should start to disappear after a while at around 850 C. I don't know what furnace you are using, but a cupeling furnace is nearly mandatory to get good results. It looks like you are not in the 850 C range for long enough, or too much cold air cooling the cupel. The temperature of the cupel needs to be in the 850 C range, not the temperature of the inside of the furnace. That would need to be higher as Yggdrasil mentioned. Picture of the furnace? Maybe see what Jason uses at Mount Baker Mining. He has a good video on cupeling on youtube. Again, the cupel should not exceed 860 C, or you will start to lose Au/Ag into the cupel. Need to regulate your temperature and minimal air flow into furnace. The bead will flash when it is done.
 
The temperature should be around 800 - 860 C. max for Au. The black scum on top should start to disappear after a while at around 850 C. I don't know what furnace you are using, but a cupeling furnace is nearly mandatory to get good results. It looks like you are not in the 850 C range for long enough, or too much cold air cooling the cupel. The temperature of the cupel needs to be in the 850 C range, not the temperature of the inside of the furnace. That would need to be higher as Yggdrasil mentioned. Picture of the furnace? Maybe see what Jason uses at Mount Baker Mining. He has a good video on cupeling on youtube. Again, the cupel should not exceed 860 C, or you will start to lose Au/Ag into the cupel. Need to regulate your temperature and minimal air flow into furnace. The bead will flash when it is done.
I'm no cupelling expert I just shared what I have read other places.
Listen to the experts;)
 
The temperature should be around 800 - 860 C. max for Au. The black scum on top should start to disappear after a while at around 850 C. I don't know what furnace you are using, but a cupeling furnace is nearly mandatory to get good results. It looks like you are not in the 850 C range for long enough, or too much cold air cooling the cupel. The temperature of the cupel needs to be in the 850 C range, not the temperature of the inside of the furnace. That would need to be higher as Yggdrasil mentioned. Picture of the furnace? Maybe see what Jason uses at Mount Baker Mining. He has a good video on cupeling on youtube. Again, the cupel should not exceed 860 C, or you will start to lose Au/Ag into the cupel. Need to regulate your temperature and minimal air flow into furnace. The bead will flash when it is done.
So no air flow? Iv had the door partially open because I read somewhere you need more air flow
 
It is a little touchy, in that you do need Oxygen to react with the Lead, but not so much that it cools the cupel. Read the Text book of fire assaying which Peterm gave a link to. Read it thoroughly at least twice. Pay particular attention to the cupeling section.
Thank you Peterm for adding that link. I lent my copy to a"friend" about 40 years ago, and never got it back.
 
easiest way to get the airflow is a couple of holes in the door that can be sealed with kaowool or a carved soft brick plug on an as needed basis
 
A great affordable kiln for assay and even small melts is made by vcella kilns. Their burnout kilns have vent holes in the door and the top to help provide the oxygen and “drive the lead”.

http://www.vcella-kilns.com/products.html
Their kilns are rugged and almost bulletproof. And even if they do fail they are easily rebuilt without much in the way of technical knowhow.
 
Here are some photos of an old school (100 years + ) commercial assay furnace, located in Leadville, Colorado. Note that the lower muffle lining is gone, but the upper cupeling liner is still intact. This was a coal fired furnace. The walls are over 1' thick. Red hard fired brick on the outside, then fire brick, then another layer of some kind of refractory insulating brick. These were used on a daily basis for firing 100's of assays per day. I bet not many still have one of these around. I wanted to build one, but DFC no longer stocks the muffle linings. Cheers to the old school.
 

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That brings back memories. Spent some time in the late 70’s poking around the Cripple Creek and Leadville area. Lots of old history in that area.
 
So no air flow? Iv had the door partially open because I read somewhere you need more air flow
MBMMLLC has perfect videos about pyrometallurgy on youtube. Watch them out, you will visually learn a lot about cupelling and smelting.

If I were you, I will try to take like 10g of lead and do a "blank" cupellation - to elucidate wheather the feed is causing problems, or you just do not have equipment/temps/oxygen right.
 
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