As a general rule we don't purchase any hollowware especially anything that is weighted. We only process knife handles and hollowware that has been split open and the weighted materials removed. Then we clean as regular scarp silver.I have never seen the degree of pre cleaning you subject your scrap to done on a commercial level. But to produce the anodes you have shown, without a flux, says it is worthwhile.
Here is a question for you? Suppose you get in candlesticks or some other sterling which has hollow filled with a waxy filler. How do you process that? Similarly, how do you process knives?
Yes, this the way to go we also use a shredder we have started using the clean shredded scarp silver to compress our anode bars in hydraulic press at 150tons and then going directly to refining. So there zero heat and or flames used in the anode bar process. And the compressed bars work exceptionally well for refining. Believe it or not this very easy and much faster than melting scarp silver.Most refiners would pass larger objects through one of these machines to make smaller pieces. (Beating a teapot like the one shown with a sledge hammer until it fits into a crucible gets old) Knives are either sliced in a shear to remove the blade or heated so the blade can be pulled free. The knife handles are then shredded to open them up so the inner waxes fall out (often wish full thinking) and then fluxed and melted.
What about other metal as Pd, Pt, Au which may stay in anode slimes? You got any or your scrap sources dont have that metals?Yes, we do things that are a bit different but that's the fun part of all this especially when you discover something that actually works. At the end of the day that's all we do is refine and mint our own AG and AU. We also have an eBay store where sell all the silver that we feel is too nice to refine. Currently we are working on granulated. and pressed anode bars as well. (so, it's all a work in progress). When the shredded or granulated bars are cleaned and highly compressed, they work extremally well not much different than a melt anode bar and better than making and using shot. I am attaching a photo showing a compressed shredder bar vs two granulated bars one compressed at 140 tons and the last one compressed at 180 tons. I know it sounds crazy but the next step for us is to compress and stamp the final refined bar which we are already working on right now.
One of the nice things about Thum cells is the ease of collecting anode slimes, you don't have to suck them out of the anode bags, you simply remove the anode fabric and burn it, pyrolytically, to reduce any metals before ashing it. That will put all of your PM's in one place to refine when you accumulate a sufficient quantity.What about other metal as Pd, Pt, Au which may stay in anode slimes?
The cells typically run 15 days. They run at 3.5 volts all the time and after 7 days or as we see a voltage drop, we gently push the silver crystals to the side, or we harvest some of the top crystals to allow more growth and prevent the crystals from shorting out at the basket.Very nice, compressed refined Silver needles should produce an interesting looking bar. At 150-180 tons of compression I assume a malleable metal like Silver will remain together well and allow for your minting marks to be pressed in.
One last question, the stainless steel bowl concept of Silver Thum cells is relatively new. And at 19 liters you are using rather large bowls. How long can the cells run before the Silver needles grow enough to short out the cell? Can you run at full power overnight or over a weekend?
Are the resin tanks changed out often? They get loaded up with both Silver and Copper and either need to be back-flushed and eluted or replaced. And do you pass your spent (after cementation) electrolyte through a resin column or treat it some other way?The rinse / wastewater is then neutralized and filtered through resin tanks and recycled back to 0 TDS (distilled water) which we continually reuse.
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