Trying to cupel

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Natez

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I am trying to cupel some brazing rods i am using Portland cement and lead it seems to be to be going very slow i have a little bead that i should be ending with .15 oz of silver and the bead is now under that weight and still doesn't look clean... i am very new to this any help would be greatly appreciated
 

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Natez

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"Portland cement and lead" describe procedure used
I make a cupell with the cement i did about a 1 to 1 ratio with 15% silver brazing rods and lead... i put the cupel in the furnace and warm it up and put the metal in it was in for 4 plus hours to get it down from and ounce to under .15 ounces and still looks like a copper ball and it is hollow inside the button.
 

Natez

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I make a cupel out of cement and set the metals ontop
Im going to try again tomorrow im just trying to work out some bugs... is hotter better? With the furnace i have should it have a constant roar because if i open up the air vents more it can sound like a train...
 

4metals

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ideally you want to cupel at 1750°F and your melt furnace exceeds that temperature with little ability to control it closely. You need more lead to effectively cupel the brazing rod for a 1 gram sample try 15 grams of lead.
But the roaring sound tells me you have an oxygen rich environment in the furnace and you are losing more Lead to the air than is being absorbed into the cupel. And the lead oxide is what absorbs the base metals and drags them into the cupel.

Too hot, too much air turbulence in the furnace, and not enough lead.
 

Natez

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ideally you want to cupel at 1750°F and your melt furnace exceeds that temperature with little ability to control it closely. You need more lead to effectively cupel the brazing rod for a 1 gram sample try 15 grams of lead.
But the roaring sound tells me you have an oxygen rich environment in the furnace and you are losing more Lead to the air than is being absorbed into the cupel. And the lead oxide is what absorbs the base metals and drags them into the cupel.

Too hot, too much air turbulence in the furnace, and not enough lead.
That makes sense i will be trying some more today but i have been wondering why it seemed like my cupel wasn't absorbing anything i will try you're suggestions... thank you
 

Natez

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Sorry the update is taking so long i was impatient and blew up my cupel 🙄... so i will be posting about my next try asap
 

GoIdman

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15% brazing bar have a lot of copper....i believe you will need a lot of lead to cupel that out... also as others stated, heat and air can mess things up.....

Be safe while doing it and good luck..
 

4metals

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I did not realize that a 15% brazing bar is high in copper. Generally for cupellation materials high in copper (as in copper based bullion) benefit from an assay process called scorification. Whereby a high copper sample is dissolved in a bath of molten copper in a melting dish with a little borax sprinkled on top. This isn't as difficult as it sounds, just add granulated lead, your sample, some borax and heat it, usually for 45 minutes to an hour while driving the lead by keeping the door ajar. This process is effective in driving the copper into the slag layer that forms. The remaining molten lead which holds the PM's is poured into a cone mold and cupelled normally after it has had any slag removed.
 

Natez

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Ok guys any help.. i turned down air flow kept the metal a liquid only saw some beads form and didn't see them roll off... smoked good when i shut it down
I did not realize that a 15% brazing bar is high in copper. Generally for cupellation materials high in copper (as in copper based bullion) benefit from an assay process called scorification. Whereby a high copper sample is dissolved in a bath of molten copper in a melting dish with a little borax sprinkled on top. This isn't as difficult as it sounds, just add granulated lead, your sample, some borax and heat it, usually for 45 minutes to an hour while driving the lead by keeping the door ajar. This process is effective in driving the copper into the slag layer that forms. The remaining molten lead which holds the PM's is poured into a cone mold and cupelled normally after it has had any slag removed.
I will be trying to get some borax this week and giving it a try thank you.. i will update again...
 

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Natez

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I did not realize that a 15% brazing bar is high in copper. Generally for cupellation materials high in copper (as in copper based bullion) benefit from an assay process called scorification. Whereby a high copper sample is dissolved in a bath of molten copper in a melting dish with a little borax sprinkled on top. This isn't as difficult as it sounds, just add granulated lead, your sample, some borax and heat it, usually for 45 minutes to an hour while driving the lead by keeping the door ajar. This process is effective in driving the copper into the slag layer that forms. The remaining molten lead which holds the PM's is poured into a cone mold and cupelled normally after it has had any slag removed.
So will any borax powder work? Like the cleaning supply or does it have to be specific for smelting???
 

4metals

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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. If you use it it will foam up as the water is driven off, which is why it isn’t used in assay flux unless it is anhydrous.
 

GoIdman

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#Natez

If you would like to process brazing bars, one way to do it safely is by using an electrolitic cell with the brazing bars as anode, copper sheet as cathode and copper sulfate as the electrolite.... A power supply ( I have used an old NOKIA cell phone charger 5V/1A)... It takes time but there is no extra effort and costs whatsoever.
After you collect the dirty silver in form of black residue from the bottom of the cell you can easily use cupellation to purify it since it will contain very low concentration of copper.
I have processed 15% and 35% brazing bars this way...less headaches with copper.

Pete.
 

4metals

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Goldman said:
If you would like to process brazing bars, one way to do it safely is by using an electrolitic cell with the brazing bars as anode, copper sheet as cathode and copper sulfate as the electrolite.... A power supply ( I have used an old NOKIA cell phone charger 5V/1A)... It takes time but there is no extra effort and costs whatsoever.
After you collect the dirty silver in form of black residue from the bottom of the cell you can easily use cupellation to purify it since it will contain very low concentration of copper.
I have processed 15% and 35% brazing bars this way...less headaches with copper.

This is a much better option than cupellation and led fumes. It will also get you paid on the copper. If you need more details go to the library section and look up the copper electrolytic cells.

Cupellation is a valuable tool for quantifying the material before purchase but for recovery Goldman is right on.
 

Natez

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Ok after about 24 hours i have a thick layer of fuzzy green/blue stuff is this working i know it takes along time i just want to make sure im on the right track befor making a bigger batch... the cathode is a copper pipe and has turned black and the anode is a stainless basket that started with 29 grams of rod in it and the rod has become brittle in places
 

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GoIdman

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Natez,

Don`t use any other metal for anode except the brazing bars....Connect one or more (tie them together with a plastic cable binder or copper wire above the contact zone with the electolite) brazing bars directly to the anode (without the stainless basket) and the copper pipe to the cathode, make sure they never touch in solution. You have to make a 50% solution of CuSO4 which is a deeper blue than yours. Your cathoode should be pale copper color and not black.
Black residue should be on the bottom of the beaker.

Be safe

Pete.
 

Martijn

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Just cleaned my copper cell out. Over 5 kg of copper harvested. Here's my setup.
Small anode left. I had a strip with a nut on the thread to set the height of the anode. The anode bag is a fleece blanket sowed into a bag.
IMG_20211118_200907.jpg
Here's the copper on the cathode.
20210704_215417 - kopie .jpg
I coated the edges of the stainless cathodes to get the copper sheets off. They pop right off with a chisel.

IMG_20211118_200955.jpg

I use the copper sheets for the stockpot and cementing silver.
Next to the bucket is some of the anode slime.
 

GoIdman

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Nice setup, well done, congrats.

The slime should be mostly silver.

You could use a silver cell to refine it further.

Be safe.

Pete.
 
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