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Keum Boo Nightmare

#1

Hi Jenn

I often solder after applying my gold and also occasionally run into
the bubbling problem. Although, the difference is that I have been
able to solve the problem by burnishing the gold back down. I have a
couple of suggestions that may help:

  1. How thick is your gold? I use about 0.03mm. It is possible
    that your gold is too thick making it difficult to burnish back down
    once it bubbles.

  2. Are your surfaces clean? Dirty surfaces may cause poor bonding
    between the two metals.

  3. I do my burnishing on a hotplate. The kind with the open coils.
    When you have to smooth out your bubbles, after the tube is soldered
    on, could you not use a hotplate and position the tube part in the
    spaces between the hot plate coils.

  4. You might consider texturing your fine silver i.e. by using roll
    printing. I find that when I use textured silver, the gold seems to
    bond better to the silver. Could be because the textured silver has
    more surface area. Hope these suggestions are helpful.

Regards
Milt Fischbein
Calgary Canada

#2

Thanks to everyone for sharing their experiences and techniques w/
Keum-bo. I’m away for the next few days but hope to try the
suggestions offered. I guess the most heartening piece of news is
that it is probably something basic I am doing wrong and that most
people are able to solder a keum-bo piece w/out a problem. Thanks a
bunch!!! (more suggestions are welcome too!)

Regards,
Jenn Mank

#3

There have been a few posts that have suggested putting the piece
with a soldered finding directly onto the hotplate to reburnish the
gold. Using this approach, what temperature do you bring the
hotplate up to? Also, is the reason for initially placing the piece
on a steel or brass plate rather than directly over the coils because
the plate distributes the heat more evenly??

Grace, Cleveland

#4

Hello Grace and Jennifer -

I also use a metal plate with a hole in it (to accomodate findings)
on the hot plate to hold the pieces for doing keum-boo. The plate
I’m using is some kind of steel scrap metal - about 8g and maybe 3"
square maximum. It was just something I found lying around (came
with the hole even!) and it works great. I do feel it helps to
distribute the heat more evenly and is certainly a more stable
surface to hold the work while burnishing. I will apply the keum-boo
on the sheet silver before the forming process as well as after the
pieces are formed and soldered. The heat seems to transfer well even
if it is just touching the steel plate at certain points. I do
place the findings in the hole and make sure the plate is situated at
a point between the hot plate coils - so the findings won’t touch the
coils.

The way I’ll test if the piece has heated up to a good temperature
is to sprinkle a few drops of water on the metal plate and if they
dance and sizzle - it’s ready to go. (Very scientific! I have no
idea what the actual temperature is at that point.) Initially - to
save time - I will put the pieces on the steel plate when they are
cold - and go off and do something else for a few minutes. Also,
I’ve put a pen mark on the hot plate dial where I’ve learned the
temperature works really well - and hold it constant at that point.
That way - I can set it up and walk away and come back in a few
minutes ready to burnish. And, I usually do need to reburnish after
solding findings - using the pin hole technique, too.

Another advantage of burnishing the pieces on a metal plate is that
the heat is somewhat deflected from the hotplate coils - making it
possible to work a little longer (doesn’t burn the fingers/gloves as
quickly). I’ll use two tools. One to hold the piece stable and one
for burnishing. And the water is close by for constant dunking.

Tacking is also another good trick. Just rock the burnisher back
and forth in a few spots to tack down the gold foil - and then go in
and burnish it well.

It’s all very experimental. Hope there is something useful in my
wordiness. :slight_smile:

Aloha,
Cynthia

#5

I have never used anything between the coil and the item I am keum
booing. Years and years ago, I was in workshop taught by Komelia
Okim. She has a chapter in Metals Technic edited by Tim McCreight.
In it she says that all soldering musts be completed. In my
experience, it doesn’t take a lot of pressure to burnish the gold
down once the correct temperature is reached. Remember that if you
are using leaf and not foil, you should put on more than one layer.

Marilyn Smith

#6 
steel or brass plate rather than directly over the coils because
the plate distributes the heat more evenly??

I get more even heat on the steel plate plus the object is better
balanced with that cut-out for the findings. My pieces are often
irregularly shaped, leaves, etc. and the pressure of the burnisher
in unsupported areas makes the piece tippy on the bare coils. Also,
I use a woodburning chimney thermometer on the plate. The plate also
gives me a larger area to work on and I am less likely to burn my
fingers. I have been burnishing the keumboo with pyrex rods
(Lapidary Journal, Aug. 2004, p. 54) which are keeping my hands and
fingers cooler. I sometimes burnish gold onto silver for a couple of
hours at a time.

Donna inVA

#7

Grace,

I was taught to use the steel plate (you could also use brass or
copper, I suppose) because it is “cleaner” and distributes the heat
evenly over a wider area. I use the 550 - 600 degree setting on the
hot plate.

I also have some very thin strips of steel in a variety of sizes
that I use to “shim” a piece when needed. When I’m doing it this
way, I am very careful to put the shims in place and give them plenty
of time to heat up before putting my piece down, so that the heat is
even on the entire thing. You can also use good-old aluminum foil for
this, as it transfers the heat really nicely.

I don’t have a “dedicated” hot plate burner for Keum Boo – I use
the same ones for my pickle pot and liver of sulfur pot and they
occasionally get squirted or misted with a variety of other things.
So I’d rather just use a clean plate that doesn’t risk contaminating
my piece in any way.

Enjoy!
Karen Goeller
@Karen_Goeller
Hand-crafted artisan jewelry

#8 
says that all soldering musts be completed.

The idea that keum boo can only be done on finished objects is a
myth. I normally apply keum-boo to material before forging,
soldering etc with no problems. If you use enameling foil for
keum-boo you can have problems, but it is so easy to make your own
keum-boo foil (no special foil necessary) that one only uses
enamelling foil for compositional reasons (it can give you green
tones, and if you deliberately heat the metal so high that it is
absorbed into the silver, then where it is looks the same as the
surrounding metal but stays white when treated with liver of sulfur
thus giving another design option. Read this article at ganoksin for
more detail:

best
Charles

#9

Once a Keum Boo piece is finished, is there some way to protect the
depletion gilded surface so that it will stay white? The pieces I’ve
made turn grey with wear over time.

Thank you.

#10

Here are a couple of ways to tell when Kum Boo is hot enough. I,
allso, use a steel plate to heat on. If you sand a small area clean
before heating, when it turns blue, you’ve reached heat. Sound
handy? Well, I just learned a much more convenient method from our
own Elaine Luther. Keep a toothpick or bamboo skewer on hand. When
touching it to the workpiece (or was it the piece of metal for
heating on? Elaine?) causes it to turn brown or black, or give off a
tiny puff of smoke, it is hot enough. I have tried this, and found
it very convenient and effective. I touched it to the workpiece,
since I was working on a series of pieces that had, oddly enough, a
piece of tubing on the back, and therefore didn’t lie flat. No hole,
didn’t think to hang it over the edge. It worked great.

HTH! --Noel

#11 
 ...if you deliberately heat the metal so high that it is absorbed
into the silver, then where it is looks the same as the surrounding
metal but stays white when treated with liver of sulfur thus giving
another design option.

A word of warning, learned the hard way-- It seems when metals mix
on their own, they tend to make their eutectic alloy (anybody care
to support or disabuse me?)-- in any case, I have found that the
"mix" area has a much lower melting point than either of its
components, so be careful, or what you’ll get is a jagged hole.

–Noel

#12

Hello again -

My understanding/experience is that the depletion guilded surface is
like a “plated” surface -so it will definitely wear off. Basically,
it is a “clean” fine silver reminant after one removes the copper
from the sterling silver material through repetitive heat/quench in
acid/brushings. This makes it possible for the 24k gold foil to
nicely adhere to the silver. I will do the depletion guilded
repetitive steps when using sterling silver - and then, after the
kum-boo process, will proceed with my usual finishing/polishing
proceedures - which include removing firescale etc.

Then, I will finish the pieces with oxidation patinas or matte
finish or whatever. If I’m working with fine silver as a starting
metal - then the depletion gilded steps are not needed for the
kum-boo process. If I’m doing the wonderful fold forming techniques
with fine silver - then the silver seems to be adequately work
hardened to be wearable.

To me, it is important that the pieces will withstand the test of
time and wear. Personally, I have not found a way to “cure” the
results of depletion guilding. Using renaissance wax on a wall piece
that I did - did not withstand the test of time. The copper modules
were fine - but the sterling silver modules lost their original
finish. However, I do live in an environment of high humidity - and
these pieces were not protected by enclosure of any sort.

Wearing work that is depletion guilded first will definitely wear
through that layer of surface treatment. In fact, it is better to do
kum-boo on surfaces that do not experience abrasion.

Well . . .over and out for this visit.
Aloha,
Cynthia (in Honolulu)

#13 
 Keep a toothpick or bamboo skewer on hand. When touching it to the
workpiece (or was it the piece of metal for heating on? Elaine?)

Strangely, either way seems to work. At first I was putting the
skewer on the piece of 20 gauge brass I had on top of my hot plate,
but when I went back and reviewed the instructions, I saw that they
said to touch the skewer to the piece of jewelry that you’re working
on.

There’s a terrific article by Celie Fago that ran in Studio PMC on
this topic. You can read it by going to the website of the PMC
Guild and clicking on magazine, which takes you to:

http://www.pmcguild.com/newsframes.html

Go to “A Keum-boo project” by Celie Fago from Summer 2003.

And, I’ve just learned that Celie has a new book out on keum boo,
for about $16.00, available from AllCraft. (I may have read this in
the August LJ.)

I haven’t seen it, but she’s an excellent writer and teacher, so I’m
sure it’s great. I plan to buy it.

I encourage everyone to read Celie’s article and give keum boo a
try. With the right tools, it’s incredibly easy. I call it shrinky
dinks in gold.

~Elaine

Elaine Luther
Chicago area, Illinois, USA
Metalsmith, Certified PMC Instructor
Studio 925; established 1992
@E_Luther

#14

I am also concerned about the wearability of depletion guilded
silver but how can you proceed with aggressive finishing to remove
firescale on a keum-boo piece without buffing off the gold?

Grace, Cleveland

#15

Hi again Grace -

    I am also concerned about the wearability of depletion guilded
silver but how can you proceed with aggressive finishing to remove
firescale on a keum-boo piece without buffing off the gold?

Sorry, I got a little busy to respond in a timely manner. Yes, it
is tricky. One thing that I have found helpful is to use a rather
stiff mini brush on the flexible shaft with bobbing compound. Medium
bristle doesn’t do as quick a job of removing the firescale.

I’ll examine the piece under a light source that works well to see
the firescale and then mark the remaining specks or areas of
firescale with a sharpie marker. Then, just go in and remove those
specific areas with the little brush. It works great to come in with
the edge of the bristles at an angle (slightly flattening them with
pressure) and carefully polish right up to the edge of the kum-boo.
But, yep, I’ve done my share of total removal as well!

It gets a little messy using bobbing compound at the bench - but it
sure works for me. I’ll go back and forth from my polishing motor -
saves time in the long run. Definitely helps in avoiding the areas
of kum-boo.

Using folded scraps of emery paper with fingernail pressure helps to
get into small areas sometimes, too. But, for me, the flex
shaft/brush system is good.

Then just a quick light final polish with the larger buff - so as to
not remove the gold.

Hope this idea works for you.
Cynthia