Theft of planchets 1 1

[GoldFinger1969]

On 6/9/2021 at 9:41 PM, RWB said:

Using the best pure copper for 10% would produce the darkest, most orange looking coins. Adding silver lightens the color and turns it a little more yellow. Color also depends on the heat source for annealing with coal imparting a bit of sulfur and gas (methane) being mostly neutral.

If the metal is in a thick cauldron with thick metal all around....how would there be any transfer of elements from coal or natual gas heating it below ?

[RWB]

On 1/21/2023 at 6:35 PM, GoldFinger1969 said:

If the metal is in a thick cauldron with thick metal all around....how would there be any transfer of elements from coal or natual gas heating it below ?

Vapor and soot contamination among others. Annealing was done in copper caskets or later in long ovens. The purpose was to get the entire strip to the same uniform temperature. Furnaces were equipped with muffles that helped isolate the metal being melted from refractory gas from the heating source, but contamination continued until adoption of electric induction furnaces. When simply meting gold or silver, the crucibles were equipped with a lid to exclude outside gas and a flux was normally used on the surface to absorb impurities. (See the descriptions and illustrations in From Mine to Mint.

Edited January 22, 2023 by RWB