Originally Posted by
HI-TEK
If you have reactive metal contaminants in alloy, the sizzle, may be due to those metals "reacting" with the water at high temperatures.
The sizzle may be due to alloy being at high temperature.
When adding the blue salt, you should expect some bubbling. This is due to water of "hydration" of the bluestone, which has water attached to the Copper Sulphate. (Formula is CuSO4.5H2O)
The crystals contain 5 moles of water.
At alloy melt temperature, this would drive off the water from the Copper Sulphate.
Your question as to how much Copper Sulphate to use is a good one, but is very difficult to answer.
In simple terms, you would need to know the weight of impurities that is in the alloy.
Without a laboratory doing an assay, and identifying contaminants, and the percentage contained in the Lead, you are really working in the dark.
It becomes a trial some, and see the results.
My suggestion is that you start with small amounts, until you can see changes in the cast alloy.
Using excess, Copper Sulphate, does not damage Lead, but should remove all traces of base metals, and you end up with a much purer Lead, that now contains Copper instead.
How much Copper, will depend on furnacing temperature, and how much Oxidation will take place during your processing.
Sorry, but unless to have an Arc Atomic absorption Spectrograph, in your shed, you are really guessing about composition of your final alloy.