I’ve done my share of japanese copper-based alloys and the
experience was good for me. For this sort of experimantation I favour
the Satsuo Ando method of pouring a small amount say 20g into a
cotton hammock immersed in steaming hot water. The resulting button
is a lovely smooth pebble-shape which has solidified in a reduced
atmosphere and which has no sharp edges needing filing. Ref:
Metalsmith magazine, Winter 1981 vol 1, no 2.
I highly recomend you read up on the Ag/Cu binary phase diagram and
try to understand the way the alloys melt and how most have a pasty
stage. Almost all the alloys share the same 779degC solidus. Which is
probably why someone said you’d have trouble soldering some of these
alloys with high-temp solders like Hard and the eutectic. By the time
you get to a solder flow temp in the high-770s degC the joint will be
starting to shimmer.
Phase diagram: http://matdl.org/repository/view/matdl:539
While you’re at this alloying lark you can be usefully employed
making your own eutectic solder at (from memory) Ag72/Cu28: it’s the
alloy that appears in the phase diagram right where the liquidus line
plunges down to meet the horizontal solidus line.
All the Ag/Cu alloys are useful in some way or other. Don’t expect
them all to be as ductile and malleable as sterling. That Ag35/Cu65
you made will be very springy, and therefore I’d recomend you saw a
piece off and make into pin wire. It’s better than stg at doing that
job and at least keeps the whole brooch within the silver family.
If you don’t like that 35/65 piece you’ll be able to recover the
silver by remelting and adding more sil or copper to make another
Soon I bet you’ll be investigating the Shakudo alloys.