Thank-you for the advice, I'll be reading it a few time while writing my own lab notes to accompany it. I'll be sure to bring up any questions and drop them in the forum.
Elemental
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If you are serious about refining, this is a good read.
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Elemental
The book describes 2 pieces of "custom equipment" for this process. First there is a sloped angle iron slag viscosity tester. The fact that he went to such detail to describe it is quite useful. Different sweeps require different flux blends and the viscosity needs to be right to allow the values to fall through the flux and collect on the bottom. This rather crude device allows you to consistently judge slag viscosity so you know when it is right to pour. An excellent procedure to assure the guys in the shop get it right consistently.
After the slag is the right viscosity you are assured the values are on the bottom of the crucible. Because of how his shop is set up, he chooses to pour it into a very long V shaped mold with proper taper on the ends so the solidified bar will come out. He choses this method because he uses a torch to take a long thin bar resulting from the unique mold and melt it over water to create shot which he can process in acid.
Another option can be to pour the entire melt into a cone mold and remelt the bottom cone of karat scrap and re-shot it in water.
These 2 photo's are directly from Lowen's book if anyone wants to discuss the details.
I think I remembered wrong there, on the mold. There was a photo as well I think.
In jewlry they use something similar. A long thin mold with a loose heavy block that they move back and forth depending on how long they want the ingot.
The sketch of the viscosity tester is allright except for the pouring area, I did not quite get that.
The pouring area is just a wider area to make sure the pour is directed into the vee and not on to the floor. He suggests using a metal can as a scoop to measure out the flux to test because a metal can will heat up quickly and not hold up too much when you pour. Since grabbing the can can be difficult and pouring not easy I think the extension to direct the pour is warranted.
The shop that I worked with who made one of these got pretty good at judging viscosity as a result of using this fixture and needed to use it less and less. The flux will freeze up before it travels the entire length and a ratio of length traveled vs weight poured which he called run per pound of slag. It was a learning process of determining lots that had good recovery and correlating that to the run per pound calculation.
A lot of guys refine sweeps in acid and experience filtration issues and hold up of values in residues. This method was an alternative. In a time of wildly fluctuating gold prices this allowed smaller refiners a viable process to get the values out quickly and not have to accumulate a lot of prepared sweeps to ship out and wait for results.
Here is a small version of that mold being used. This is an old video from the copper cell thread days. They work great and can be made to all most any size. Another option is a piece of channel iron. The width comes in various sizes, and depth as well varies. The channel already has an angle molded to the inside that seems about right to ease the release of the solidified metals.
This is a good video showing how small this can go and adding the clamp instead of welding the ends on makes removal of bars easier. I have also seen major refiners use channel iron with flat plates clamped on the end, again making for easy removal. Molds can get pricey and channel iron has yet to catch up.
