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Keum Bo nightmare

Hi folks, My name is Jenn and I’m a jewelry student soon off to N.
Bennet St school. I have learned so much by lurking on here and have
a problem I would like to present in hopes people may offer
suggestions to help to solve my dilemma.

I have a 1" X1" sq of fine silver I keum bo 24 k on and solder a
piece of tubing on the top part of the back that I hang on a cable.
I really like the tubing on the back and the way it hangs. My
problem is the keum bo bubbles when I solder the tubing and no
amount of burnishing will alleviate the bubble. Piercing them does
not work either. Next I tried fusing the gold w/ a torch but then
completely melted the tubing. I thought about casting the piece w/
the tubing but I think the tubing will still melt as it will be
hollow. I tried to keum-bo the piece w/ the tubing on it, dapped,
but this does not work as it does not heat everything enough burnish
in the gold) I have also tried placing the tubing on the very edge
of the piece and then burnish the gold in but then I cannot dap it.
I guess my last thought it to pierce through the copper I burnish on
so the the piece lays more flat and try to burnish in the gold.
However it would then place the tubing directly on the electric
element. I would so appreciate any suggestions,

Thanks in advance,
Jenn Mank

Hi Jenn,

I’m not an expert in Keum Bo but will share what I know.

  1. It’s the last thing you do (except stone setting). You do it
    after everything is soldered together and all of your main polishing
    is done.

  2. I do it with a thin steel plate that lays directly on my
    hot-plate burner element. In the case of a piece that needs to “hang
    off” to lay flat, it’s a fairly simple matter of hanging it off the
    edge of the plate – the plate conducts the heat to the piece evenly
    and keeps the overhang from touching the heating element. I also
    have a couple of smaller pieces of metal plate that I can stack
    underneath a piece (like shims) to transmit the heat if necessary.

  3. The burnishing part doesn’t require much pressure – not like
    burnishing a bezel. You’re basically just pressing out bubbles and
    making sure that there are no gaps between the gold and the silver
    that would impair fusing.

I hope some of these help point you in the right direction. It
might help if we saw a photo of the piece if you can toss one up on a
website somewhere…

Karen Goeller

I would solder the tube on the silver square and completely finish
all filing and polishing operations. I would scrub the surface to be
keum boed (Is that a word? Sure looks funny) with my finger using
baking soda and water until the water sheets off of the entire
surface. I would not touch the surface with my skin after that. I
would lay it directly on my hot-plate with the tubing hanging
between the elements. I would probably not try to cover the surface
with an exact size foil piece. You did not say if you were using
foil or leaf but foil is better. The pieces can be lapped over each
other and should not show after burnishing. If there are bubbles,
pierce them with a needle and burnish them flat while they are on
the hot-plate. It shouldn’t be that hard to cover an inch of fine

Good luck
Marilyn Smith

the keum bo bubbles when I solder the tubing

My set-up is like this: a stainless steel piece 1/4 " thick, about
8" x 8", so it just fits on top of the elements on the hotplate.
This piece has a 1/4" x 3" rectangle cut out of it, centered on the
plate and 1" from one edge and parallel to it. The findings go into
the cut-out, the soldering is done first, the piece rests flat on
the stainless steel plate and heats evenly. I do earrings, pins and
pendants this way. If I’ve soldered wires on earrings for hooks to
be formed later, I leave the wire straight for keum-booing.

Donna in VA

Jennifer -

It sounds as if the Keum-boo foil was not well adhered when it was
originally applied. You should be able to solder the tube without
problem. I regularly do far more construction than that on my pieces
and have, at most, small bubbles that are easily burnished out.

I would go back to the application of foil to the flat 1" square of
silver. Is enough fine silver raised on the surface (I heat and
pickle about 6-7 times/piece)? Is the surface uniformly clean? Is
it uniformly flat? Is the Keum-boo foil clean? Is there enough heat
(Keum-boo foil bonds at around 650 degrees F)? Finally check that
you are burnishing evenly and with enough pressure (really push). I
suspect one of these is the problem.