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Kumboo


#1

Greetings List: I’ve been reading about Kumboo and tried it using a
lab hotplate with a flat, cast metal surface. I also have ceramic hot
plates that could be used. The 22k gold was rolled very thin,
somewhere on the order of .01mm. The Au was burnished with pressure,
and then rolled for a surface pattern. Most seems to be adhered, but
some edges appear to be lifting. I am hestitant to polish this…any
suggestions? I also have 2 questions:

1] Are these hot plates “hot” enough? For successful fusing…and

2] Can thicker pieces of 22k Au be fused? With what changes to the
procedure? Once again thank-you for all your wonderful advice. From a
grateful student…

–Barbara


#2

Use 24K sheet .03 to .05mm. I don’t think you can get the same
adhesion with 22K since it’s not as soft and maleable. You might read
Komelia Okim’s Kum-Boo chapter in METALS TECHNIC edited by Tim
McCreight. Donna


#3

Use 24k gold, not 22 for easy application. If it is lifting your gold
is probably too thick. Almost all adhesion problems I have seen are
because the gold is too thick.

Read lots more on Keum-boo on my article at:

charles

Charles Lewton-Brain
Box 1624, Ste M, Calgary, Alberta, T2P 2L7, Canada


#4

Barbara, The trick to successful Kumboo is heat! For the gold to
adhere, the piece must be hot enough for the gold to fuse or adhere
to. What I do is, depending on the size of the piece, lets say
earrings. I heat up a piece of bronze with the earrings on it (using
a torch) a then when the bronze is real hot, I direct the flame to the
earrings and gently heat—not to anneal or have any red color, then
when hot , I take away the flame and add the gold and burnish. When
I’m done with all the gold I’m going to add, I re-heat the piece and
check for bubbles and re-burnish the gold - bubbles or not just to
make sure the gold is fused. Be careful not to over-burnish or you
will lose the texture of the silver. Hope this helps. Any questions
contact me. Lisa P.


#5

I would suggest that your kum boo has not fused to the whole area. It
is always difficlt to fuse sections like this. However…clean the
piece thoroughly in pickle/alum etc and then bring up the fine silver
surface again, and then burnish/fuse to the fine silver. Be patient
and do bring up the fine silver at least ten times!! I find sometimes
if is better to overkill than underkill. ie if it does not work with
ten surfaces of fine silver it will never work!!! wheras if you only
did five…

Are these hot plates "hot" enough?  For successful fusing....and 

Yes if you get them hot enough.

   Can thicker pieces of 22k Au be fused?  With what changes to the
procedure? Once again thank-you for all your wonderful advice. 

Barbara I have only ever used 24ct gold from thin to thicker pieces,
perhaps your gold might be the problem. I use kum boo extensively in
my work.

Felicity in sunny West Oz


#6

Barbara, hello. I have some suggestions that may help you with
kumboo. I have worked with 24K gold, and 23K gold which was alloyed
with fine silver, but not 22K. About the hot plate—I use a hot
plate with a calrod burner as I can put curved or domed items in the
depressions and they do do roll around as much as they would on a
flat plate. I heat it very hot—maximum, and let the piece heat on
it so that when I start burnishing it is thoroughly heated. Kum
boo holds best on a textured surface, as the gold gets pressed into
the grooves during the burnishing. The gold tends to lift when cut
with sharp corners, but these can be burnished down after the
initial burnishing. The important thing is maintaining enough heat
on your stove. Start with high, then you can turn to medium during
the burnishing. Regarding the thickness of the gold—if it is too
thick it will not adhere—thinner is better. Getting the correct
thickness is important—too thin and it will disappear into the
silver, too thick and it will not adhere. Some pieces with sharp
corners will need repeated burnishings so be prepared for that. To
summarize the two most important things to keep in mind is lots of
heat, and correct thickness of the gold. It should be about the
thickness of medium weight aluminum foil. The gold used for
enameling is too thin. It must be thicker than that. In addition to
using my regular burnisher for burnishing, I use a dental tool with a
tiny round spoon shaped bowl, and use the rounded part to burnish
places the big burnisher may have missed, and I go around all the
edges with it. Good luck, and if you any more questions you can
contact me thru the Orchid bulletin board, or at arands@aol.com.
Alma


#7

You can’t use 22K gold. Only 24 K works… I made the same mistake.
Only pure gold works.


#8

Hi - This new kum-boo string brings to mind a different question -
same subject. Does anyone have a recommendation (and hopefully a
source) for gloves to be used during the kum-boo process? The gloves
that were recommended in our kum-boo workshop here were made of a thin
cotton material. The thinness of the material gave more tactile
control than a thicker more heat resistant glove. However, the heat
transfer makes it difficult to stay with the burnishing process for
longer stretches of time. I have been constantly on the lookout for a
better glove solution - and haven’t come across anything yet. Thanks
ahead - you all are great. Cynthia


#9

Barbara,

I’ve had excellent results with keum-bu by using the following
methods:

  1. Depletion gild the surface of the silver (very important to the
    success).

  2. Roll 24 ga. 24 kt. gold to about the thickness of Reynolds
    heavy-duty aluminum foil.

  3. I roller print the pattern on the silver before fusing the gold.

  4. I have a gas stove. I use a circular piece of 1/2" thick aluminum
    (some of my friends use copper) on top of the flame, about 6" in
    diameter. I put the pieces on the plate with the gold in place, turn on
    the fire, and go do something else for about 20 minutes, until the
    pieces come up to fusing heat.

  5. I reduce the flame and burnish with a curved steel burnisher. Not
    much pressure is needed if your pieces are hot enough.

  6. Turn off the heat and allow the pieces to cool. Inspect the edges
    with the Optivisor. If all the edges haven’t adhered, go back to step
    4 and repeat.

  7. Once fusing is complete, and you intend to do any forming or
    folding, anneal the pieces several times before proceeding.

  8. Burnish the piece with a brass brush and soap. Patinate. No rotary
    polish needed.

Hope this helps. K.P. in WY


#10

Cynthia, Clean cotton garden gloves are the ones I use----I keep a
bowl of water nearby to dip my gloved hands into when the heat is on !
Lisa Pilchard


#11

Several months ago, a kumboo topic was discussed and several karats
of gold were used for the gold used in kumboo. I was surprised that
you could use 18kt, 22kt, etc. The only drawback with the lower karats
was that over time the silver would diffuse through the gold and cause
a color difference. Lisa Pilchard


#12

Try a store that caters to race car enthusiasts. They sell very thin
"hot gloves" for working on hot engines during races. I can’t remember
what the insulator is but it’s pretty good, I know people who use them
for welding steel.


#13

Hi Katherine, How high do you turn the heat up on your gas stove?
Thanks for the info! Nina Nina L. Olney Thank you from Arizona
Looking for the Olneys/D’Olley/D’Oilly etc.


#14

Dear Cynthia, I dont use gloves… and must admit would find it
very foreign not to be close to my materials… however consider using
a burnisher with a wooden handle, and something similar for holding
the piece still . You could also try having a bowl of water handy to
cool the tools.

Felicity in West Oz


#15
   You can't use 22K gold.  Only 24 K works.. I made the same
mistake. Only pure gold works. 

22K WILL work, but only if the alloy is only gold and silver, with no
copper. Kumboo works because at these elevated temperatures, both
gold and silver are quite permiable to oxygen, and the gold allows
oxides/oxygen on the silver surface to dissipate into the gold and
through it, much like a flux would do in cleaning the silver. The
result is chemically clean metals, and gold and silver have similar
enough sizes of atoms that they easily interpenetrate each other, so
it does not take much, once the metals are clean like this, for a
metallic bond to take place. Copper has a different enough size of
it’s atom that it will block that bonding process if it’s in either
the gold or the silver. this is why you have to deplete the copper
from the silver surface before bonding the gold. But a small
percentage of silver won’t stop it from happening, so a 22K
silver/gold alloy can work. however, pure gold is softer and more
malliable, so it’s easier to burnish down tight to the silver.
Without the pressure of the burnishing, you don’t get good adhesion,
and a 22K silver/gold alloy, being slightly harder, will be more
difficult to burnish down completely.

Peter Rowe


#16

Cynthia The kind the sell to marching bands are heavier and would
protect for a longer period of time. Also those thin white gloves
used by caterers for their waiters could be used by putting two
gloves on each hand. J.Z. Dule


#17

Cynthia, Clean cotton garden gloves are the ones I use----I keep a
bowl of water nearby to dip my gloved hands into when the heat is on !

uhm, forgive me for asking…are you aware that water is a conductor
of heat. try pulling something out of the oven with a wet potholder.
you wont try it more than once. Michael / QuestFox


#18

Joan I have sucessfully and rather easily adhered various Karat golds
to sterling (with a fine silver raised surface) I’ve made many
different alloys in an effort to get a varied palette of colors, and
they all work! BUT there is no copper in those alloys. I also have
adhered commercial 18K alloys. You have to treat these as you do the
sterling base piece.Multiple heating and pickling to leach out the
copper and then apply as you do with 24K gold.The exchange of atoms
across the interface of the two metals can take place if the intimate
contact is maintained by burnishing with minimal heat to increase the
velocity of the atoms, AND there is no barrier of copper oxide to
prevent this interchange!

Charles N. Brain mentions this in his paper on Kumboo.

I hope this has been helpful! J.Z. Dule


#19

Some friends and I are getting together soon to teach ourselves Kum
Boo. None of us has done it before, and we will be armed with Komelia
Okim’s article, as well as numerous Orchid posts in this thread and
the previous one a few months back. I have a couple of questions:

Because not everyone in the group has access to a rolling mill and
our time together is limited, we’ve decided to try the method with the
gold foil that enamelists use. I realize this is very thin compared to
the weight foil most of you are using. However, Okim says in her
article that it’s possible to do the process with the foil, although
several applications are necessary. Also, it seems there would be
various subtle color variations as the gold is layered and diffuses
into the silver, and this could be interesting.

Have any of you tried the foil method, hopefully with some success?
How might the procedure need to be modified when using the foil? Are
there any specific suggestions you can make, pitfalls to avoid?

Also, pertaining to the article, she uses gum tragacanth (as an
adhesive, I assume). None of you has mentioned that you use this in
your process. Is it necessary?

Thanks very much for your help! I’ve really learned a lot from
reading this thread.

Rene Roberts


#20

Michael, You are correct, water is a conductor of heat. But, nothing
feels better when your hands are hot and you quench them in a nice
cool bowl of water! Since this thread started, I have learned of other
types of gloves to use and will give them a try. Lisa Pilchard