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Blackening copper but not silver solder


#1

Hello:

This is my fist post so I’d like to take a moment and extend a thank
you to everyone who has shared their knowlegde freely and
unrestrained. I think it is fantastic. I hope I will be able to offer
some assistance in the future.

I am asking a question for our jewellery departmetn at NSCAD because
we are stumped.

Along with many other techniques we teach solder/metal inlay. I
number of students have expressed an interest in blackening copper
pieces with silver solder inlay so that the copper is a rich black
and the silver solder a bright white.

Here is what I know/have tried:

  • I know that liver of sulphur, the Jax blackening solutions and
    Rokusho all create great patinas but all of them either colour the
    solder or are not black on copper.

  • I have been searching out the proper recipie for Korean "Black C"
    I have tried Mr. Lewton-Brain’s (18%sodium hydroxide solution 18g
    sodium hydroxide and 100cc distilled water) to no avail and I have
    also tracked down with the aid of our faculty member Kye-Yeon Son,
    the author of a Korean patina book which listst the recipie as 5:1
    sodium hydroxide to sodium chloride. But there is no indication of
    concentration of the sodium hydroxide. When we contacted the author
    he said that he had gotten the recipie from industry in Korea (where
    Black C can be bought pre mixed) and does not know the concentration.

  • I’ve tried heating solutions and dipping, heating pieces and
    dipping or both. I have managed to get some pretty cool colours but
    not what we have been looking for. I am hesitant to mix up any more
    chemical as it is not my favorite thing to do, especially when I am
    responsible for the students around me.

I am wondering if the key has to do with the zinc in silver solder,
that is probably what is turning colour (usually the silver solder
goes yellow-brown).

Does anyone have any suggestions?

many thanks,
Georgia


#2

Baldwin’s Patina won’t coler silver, but it turns anything else
anice brown or black. I don’t know what’s in it, but you can get it
from reactivemetals.com and it’s fairly cheap. They usually are
pretty knowledgeable about the stuff they sell, so maybe you can ask
them what it is or something. I’ve used it for quite awhile on mukume
gane and solder inays, and it worls like a charm. A little goes a
long way.

Hope this helps, good luck!


#3

white gold solder. more costly, but with LOS (which won’t affect the
gold) should get the look you want

cheaper alternatives…stop off lacquer on the silver solder, LOS,
then strip the lacquer…or…selective polishing of the silver
solder after LOS

I’ve never tried it but if there was a way to use fine silver for
your inlay instead of silver solder you could just LOS the whole
thing and the fine will not take color from the LOS

The gold solder bit will probably live longer in the real world as
far as discoloration. Silver solder would of course tarnish pretty
quick, making maintenance a chore and risk eventual wear on the
adjacent colored copper from rubbing with a cloth or whatever. A
little rhodium on top of the gold would be a distinct plus.


#4

Georgia-

I have an idea for you, but I’m not sure if my is
completely correct. As I recall, you can cut a daikon radish and rub
it over the piece, then use liver of sulphur. I think that this
keeps the silver nice and clean, and allows the copper to oxidize
black.

Another thought would be to give Reactive Metals a call and see what
they know. They sell a copper/sterling bi-metal, which I have seen
etched and then oxidized so that the silver stays white. If I am
recalling correctly, the process mentioned above is the way this is
done.

Best of luck to you!
Erica Duffy


#5

Whatever you use to chemically blacken the copper is going to affect
the silver solder simply because a percentage of the solder is
copper! The best solution may be to apply a temporary resist to the
silver solder before blackening the copper with LOS or one of the
commercial solutions. Clear nail polish should make a reasonable
resist and could always be left on as a protective lacquer.

Best wishes,
Ian
Ian W. Wright
Sheffield UK


#6

Ashley,

Baldwin's Patina won't coler silver, but it turns anything else
anice brown or black....I've used it for quite awhile on mukume
gane and solder inays, and it worls like a charm. 

Neil brought up an interesting thought, though, how does one then
care for the piece if the silver tarnishes & you don’t want to remove
the surrounding blackening of the copper? I’ve never done solder
inlay, but this discussion has me intrigued. I guess it would look
nice, too, if the copper wasn’t blackened, but I kind of like the
idea of the black & silver, at least as an option.

Thanks!

Lisa
Designs by Lisa Gallagher
www.designsbylisag.com


#7

Hey Lisa

I usually just polish the whole piece, and re-patina. You might be
able to laquer the surface to preserve the patina and the silver
color, but I have never tried that.

I use hard or IT solder for inlays because of the high silver
content, then depletion guild the solder. It’s a little tricky
because of the flow point, but if your copper is thick enough it
works just fine. Both the silver and copper will tarnish, and I guess
there’s no getting around that, but it’s really easy to polish up and
a little Baldwin’s goes a really LONG way.

Hope this helps:)
Ash