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[Source] Red Bronze, Tombac


#1

A customer wants me to cut parts in what she called ‘Tombaga’, wh=
ich I’d never heard of. An intensive, five-minuter scouring of the
internet(s) told me that ‘Tumbaga’ is an alloy of Cu and Au, which I
quickly ruled out, since this person makes inexpensive Cu jewelry. A
reference to’ Tombac’ as a copper alloy used to imitate gold was
found, and this seems like the most likely suspect. AKA red bronze,
Dutch brass, German brass, like, 84-90% Cu, 16-10% zinc.

So, without spending another five or ten on another extensive
investigation the question is, where can we get sheet. (and no,
nobody is allowed to laugh if it turns out to be something ubiquitous
like red brass or yellow brass or Ok Gold)((oh, ok, maybe a little))

Dar
www.sheltech.net


#2

Hi Dar,

“Tombak” is a German term for a red brass.

I’ve got German references to it that talk about 'tombak that has
90% copper" and another ‘tombak’ alloy that has 72% copper, but the
text makes a distinction between those two ‘tombak’ alloys and brass
(Messing), so there’s something different there as far as they’re
concerned, but it’s not obvious what that may be. I also get the
sense that Tombak is sort of limited to cheap jewelry, like the way
pot metal is in the States, but that’s just a sense.

Brepohl lists it as a 90%Cu/10%Zn red brass, and mentions that it
can be brightened by dipping it in peroxide pickle. (Pg 67.)

For the purposes of your customer, I’d figure red brass (or just to
be snooty, “Gilding metal”) would do just fine. (Or NuGold, which is
about 88/12)

FWIW,
Brian


#3

I sell shapes cut out of Tumbaga as it is called here in Mexico, I
know it is not red brass at least it doesn’t look the same as the
sample of red brass I have here. I can’t get red brass, we have
copper, yellow brass, tumbaga and Nickel silver as base metals here
in Mexico. I will be happy to sell you sheet, it has a lovely rich
golden color. It happens to be my favorite of the 4 metals. In my
website I sell it under bronze. Hope this helps.

Sincerely,
Laura Brito


#4

A few years ago I did the tombac search as well. The requirements
were 6 pieces of sheet stock aprox 5" x 5" x 1/8" thick that could
be enameled.

Reference books indicated that “tombac” or “guilder’s metal” offered
superior results rather than working on copper. Superior because
colors such as transparent reds or purples wouldn’t muddy as with
copper. To all you enamelists out there…I didn’t have the
luxury of being able to apply the colors over flux. The traditional
tombac is 95% Cu, 5% Zn.

The website copper.org offered a wealth of for all sorts
of alloys but in calling all over the USA I couldn’t find a supplier
for the thickness I needed. That’s not quite right…did find a
couple suppliers that quoted minimums that were WAY out of range for
me. Did find one but was told they produced that stock exclusively
for one customer.

Learned that Thompson Enamel carried [carries] tombac but their
standard stock was much thinner than my requirements. Bought some to
experiment and really liked the results. Don’t know why any
enamelist works on copper when superior results can be had from the
tombac. The zinc in the alloy does give the raw metal a golden
rather than pink coloring

Also spoke with a production house for badges [forrestry, police,
fire etc]. They had similar needs but used opaque enamels and my
goal needed a transparent. They said they used the brass alloy #220
[90% Cu, 10% Zn] Also indicated it was easy to obtain through
McMaster-Carr. Found this to be true, ordered some, finished the
project and now use the #220 whenever I can.

Orchid Rules…Karla Maxwell from So. California