Ok, I don’t have the text handy, and I have no time to find it either
(I fly out to the US Wednesday and have obviously put it into
storage), but from (rather dim memory) the amount for brass/bronze
casting is 15-30g/100kgs of phosphor copper. This depends on how
clean the material for ingots use less and for scrap use more, so in
any case it’s not much.
The text I’m referring to is C.W. Ammen’s “The Complete Sand Casting
Bible” and I think the amount was given in oz/100lbs, so my memory is
based on a figure I derived, and it’s been ages since I last looked
in the book, so I’m not 100% certain…
That said for a #6 crucible (would hold 8.6kgs of bronze) I use 3-5
granules, 3 if the bronze is clean ingot, 5 if scrap/remelt, no
brittle casts nor any bubbles/porosity so I must be pretty close!
The below is dangerous info, moderator may choose to edit or remove
BTW if you like to live dangerously 1.5% to 7% arsenic (DEADLY fumes
given off when heated) can be added to make it pour a bit better (not
a huge improvement), and with no real change to the appearance and
workability of the metal. Please DO NOT DO THIS, it’s just some
trivia I’ve picked up from studying the history of metal usage by
man, and I only mention it as by the by thing seeing as there are
many metals that can be added in quite small amounts to make copper
more “foundry friendly”, arsenic is just one extreme example. Some
other metals aRe: lead, antimony, tin, zinc, iron, aluminium,
silicon (1.5% tops IIRC), beryllium, oxygen (increases the
conductivity when added at up to 1%, don’t ask me how they do that!)
well you get the idea the list is just as long as the periodic table,
within reason anyway.
Cheers, Thomas Janstrom.