Re: [ATM] Dense

["John Sherman" <atm@mail.johnspics.com>]

Hi Anthony,

Thanks for giving us the update and lesson. 

>  Two thirds copper, one third tin.  What is it?

There is a very nice article by Peter Abrahams in the ATM Journal #16 pg 21 called "John Mudge on Mirror Making 1777". Peter says for a 4" diameter mirror Mudge would "cast 13.5 ounces of tin with 32 ounces of Swedish copper to make an ingot. Some of the tin, however, would evaporate from molten copper and leave pores in the process. He then remelted that casting (at a lower temperature than the copper) and added another ounce of tin. This alloy would then be cast into a hard, white, fine-grained speculum."

Maybe something there will help?

He mentions that others used the arsenic to prevent tarnishing, but you had to hold your breath while working with it! He used lead and brass tools. Some people think Couder invented zonal masks, but there is a picture of the zonal masks Mudge used. Mudge documented his techniques in "Philosophical Transactions of the British Royal Society for 1777", volume 67, pages 296-349.

Have fun,

John



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