Smelting in India

[4metals]

Don't forget the manure!

If you are using litharge you want to use a source of carbon as a reducing agent in the fusion. Manure works, flour will work better. I would make a flux blend with one part borax, one part soda ash, 1/8 part fluorspar, and 1/8 part flour. I would start with 1 part litharge and see how effective that is. Litharge is your costliest ingredient so you want to use as little as possible but enough to be effective. The more you use, the more you have to absorb into the bone ash hearth and the more is volatilized in the cupellation process.

If you start with well mixed IC ash you can mix up flux with no litharge but everything else, then run 1 pound with 1 part, and one pound with 2 parts and 1 pound with 3 parts of litharge. Compare the results and use the least litharge that captures all of your values.

 

[gaurav_347]

Sir,

Thank you once again. I shall try this out in the coming week and report back with my results . One last query, After cupellation is there any way to recover and reuse the absorbed lead from the cupel?

Regards,
Gaurav

 

[4metals]

The lead absorbed into the cupel is contaminated with all of the base metals that it carried with it. While it may be a good feedstock for someone specializing in lead refining, it isn't something I would get involved with.

 

[gaurav_347]

Sir,

There are three types of lead oxide available. One is yellow in color another one is red in color .These two variants cost 3.5 usd/kg. The third one is Blackish to Greenish Grey in color.This one is called lead suboxide and is available for 1.2 usd/kg.

The confusion is which one to use here for smelting ics.

Thanking you,
Gaurav

 

[4metals]

I have used the red litharge and the yellow litharge interchangeably for fire assays. I have never heard of lead suboxide but if it is the cheapest I would try it. Add just a bit more reducing agent (carbon flour or dung) to help it give up it's O₂.

There is a technique when performing fusions in sweeps assays where you calculate the reducing power of the flux mixture you are using. You can increase the reducing power of the flux by adding additional carbon. I would be determining the reducing power of your basic flux mixture and adding additional carbon to maximize lead reduction. Then I would use that mix for your process keeping the ratios of flux to material you are processing constant.

 

[goldsilverpro]

I have used the red litharge and the yellow litharge interchangeably for fire assays. I have never heard of lead suboxide but if it is the cheapest I would try it. Add just a bit more reducing agent (carbon flour or dung) to help it give up it's O₂.

There is a technique when performing fusions in sweeps assays where you calculate the reducing power of the flux mixture you are using. You can increase the reducing power of the flux by adding additional carbon. I would be determining the reducing power of your basic flux mixture and adding additional carbon to maximize lead reduction. Then I would use that mix for your process keeping the ratios of flux to material you are processing constant.

The ancients used the lees from wine making to reduce the lead in assays. I always used white sugar.

 

[gaurav_347]

All,

Apologies for not updating this thread. Due to holidays here most of the shops were shut .I was finally able to source all the fluxes required. I got 50kgs of bags of each type, namely lead oxide, borax,soda ash, fluorspar powder, tricalcium phosphate and a bag of portland cement to make my own cupels.

I also got a small coal fired furnace made which hold 20# crucible to do my test batches on the ic ashes. The furnace costed me roughly 50 usd to manufacture. I tested it to melt some copper fines that we recover from pcbs. The furnace melts the copper in under 15mins of starting it .

I will be performing the test on ic ashes in this week and update here .

 

[gaurav_347]

Don't forget the manure!

If you are using litharge you want to use a source of carbon as a reducing agent in the fusion. Manure works, flour will work better. I would make a flux blend with one part borax, one part soda ash, 1/8 part fluorspar, and 1/8 part flour. I would start with 1 part litharge and see how effective that is. Litharge is your costliest ingredient so you want to use as little as possible but enough to be effective. The more you use, the more you have to absorb into the bone ash hearth and the more is volatilized in the cupellation process.

If you start with well mixed IC ash you can mix up flux with no litharge but everything else, then run 1 pound with 1 part, and one pound with 2 parts and 1 pound with 3 parts of litharge. Compare the results and use the least litharge that captures all of your values.

Sir,

When you say one part do you mean 1:1 ? For example if one kg ash needs to be smelted then 1kg of borax one kg of soda ash and one kg of litharge and so on?

Thanking you,
Gaurav

 

[gaurav_347]

Some pictures of the coal fired furnace.

 

[4metals]

When you say one part do you mean 1:1 ?

When I was describing a ratio for making up flux, 1 part is whatever convenient measuring device you want to use. For example an empty soup can is typically used. So if the formula you are using is what I posted;

1 part borax
1 part soda ash
1/8 part fluorspar
1/8 part flour

You add 1 can of fluorspar, 1 can of flour, 8 cans of borax, and 8 cans of soda ash. Then you mix it well and this becomes your basic flux LESS the litharge. I would start with adding litharge to the mix (starting with 1 part, 8 cans) and doing a test melt. Then you slowly lower the litharge until you get it to make a nice fluid flux with as little litharge as possible. This mixture will become your flux for this process (So note the final quantity of Litharge that ends up working the best.)

Start with a small measuring can so you make up a small amount of flux enough to handle 1 or 2 melts. When you determine the proper litharge ratio for your ash, switch to bigger cans and make up a stock flux. The ratio is the same based on the number of cans used, flux made using a small cup for each ingredient measured in, will be the same as flux used with large pails as your measuring cups, as long as you do the same counts of each component.

Next you have to address the ratio of flux (what you made from what I described above) to ash. So if you want a 1:1 ratio of ash to flux, use 1 can of blended well mixed flux (with litharge) to 1 can of ash.

These formulations are based on volume of the material, not the weight of a can of each material. Some fluxing formulations go by percentage of each ingredient, and those generally go by weight. This formulation, for simplicity, is by volume.

 

[4metals]

I should add that a lot of smelters mix up large batches of flux so they have a prepared stock flux. They mix it in a cement mixer, or a clean ball mill if they have one.

One issue is the flux can be dusty, and if some of the dust is from litharge, there are inhalation health hazards. One way to keep down the dust is to add some cooking oil as a dust suppressant. I generally add 600 milliliters per 100 pounds of flux or there abouts. Add it slowly as it tumbles and it will mix in nicely and keep the dust down.

 

[gaurav_347]

All,
I Finally did a test batch today of smelting ic ashes. The total weight was 1.520 kgs after removing the magnetics. The total ashes were 4 parts. I added 4 parts of flux recipe to it. I made the Flux recipe as per the guidance of 4metals. I made a huge blunder of not adding silver while cupellation to collect all the precious metals while cupelling the lead dore. This didn't help collecting the gold as you can see in the picture attached. Since this was a small batch for testing I am planning to add silver the next time during cupellation.I made the flux recipe as recommended except that I added 6 cans (parts) of lead oxide instead of 8. I did add an extra part of carbon (wheat flour). After the smelt i recovered 250gms of lead in the cone mould. I did a resmelt of the slags with fluorspar and soda ash (1 part each)and recovered a few beads of lead. I guess a bigger batch like 10kgs-20kgs of ashes will give a clear output. Here are some pictures. Please advice If any changes need to be made. Thank you for all your help once again.

Thanking You,
Gaurav

 

[4metals]

How fluid was the flux?

 

[gaurav_347]

Sir,
The flux wasn't as fluid as I expected it to be. I did add an extra part each of fluorspar powder and soda ash to the smelt but it didn't affect much.

Regards,
Gaurav

 

[4metals]

With equal parts of total flux to ash that isn't a surprise. But if you aren't holding up a lot of beads in slag, it isn't a problem.

One thing you can experiment with is increasing the reducing power of the flux. This is often done with assay fluxes to maximize the weight of lead brought down in the fusion. It is done by incrementally increasing the flour until the size of the lead button doesn't get any larger.

 

[gaurav_347]

Sir,

Do you suggest we increase the flux to ash ratio or should i make any changes to the flux recipe? I will try using extra carbon the next time I smelt the ashes. There were a lot of beads left when we re smelted the slags.

Thanking you
Gaurav

 

[Lou]

I think you'll have to resmelt the flux and thin it out with soda ash. It's been my experience that if the flux is reducing and extra carbon is present, there will be some level of precious metal hold up in the slag because of carbon dioxide gas keeping it suspended. In practice, it will look like small flames popping from the flux surface.

 

[gaurav_347]

Sir,

I did resmelt the flux with 1 part fluorspar and 2 parts of soda ash. The smelt wasn't as thin as i expected it to be . After the pour this time in a regular mould, I discovered some beads large in size after breaking the slags with a hammer. The smelt was bubbling and not watery as described here in some of the threads. the soda ash that I am using is light soda ash. What seems to be the mistake i am making here?

Regards,
Gaurav

 

[gaurav_347]

All,

Can i simply use lead metal instead of litharge along with the fluxes?

Regards,
Gaurav

 

[kjavanb123]

Hi,

In an attempt to minic the experiment in this post,

I finished lead smelting sample IC ash. Plugging ratio suggested by 4metals, and kurtak in their posts. Here is what I got so far.

ICs ash, consists of everything, legs, bond wires etc and ash, weigh 90 grams. Mix of different grade ICs.

Stock flux was prepared by adding 100 grams of soda ash, and 70 grams of borax, 20 grams of fine glass.

About 112 grams of that stock flux was twice the volume of 90 gram IC ash. It turned out during smelting, I needed more, maybe 3:1 volume to ash.

After mixing everything up, total weighed 351.2 grams. According to kurtak, suggesting 30% of total mix mass is the weight collector metal.

Since I was using lead in form of lead oxide as my collector metal, therefore I would need 30% of 351.2 grams, or 105 grams of lead.

There is 98.2% of lead oxide that is lead, therefore I need 110 grams of lead oxide.

In order to reduce 110 grams of lead oxide to lead metal, I used 10 grams of flour.

Mixed them well, heated up crucible, and kept adding materials to and pour into my innovative iron mould which I seasoned with oil.

Here are some photos,

My test furnace, burner designed based on youtuber, king of random, and the furnace body is lifted and I can access the cruicble easily,


Molten material poured into conical mold,


Slag seemed black and glass like as mentioned by 4metals,


I will be doing cuplation tommorow.