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Keum-boo hot plate


#1

Hello to all,

I’m looking to try some keum-boo on a hot plate.I have done it
before using a torch and in Celie Fago’s book Keum-Boo on Silver she
recommends a 1000 or 1100 watt coil hot plate and then making a coil
cover.I have a 1300 watt plate with a solid cast iron top and a wood
stove thermometer to find the correct heat range.I would also like
to use Argentium Sterling,so my questions are these, 1.Has anyone
used a cast iron hot plate and if so any problems or
recommendations?

2.Is there anything special I need to do to the Argentium to get a
good bond with the gold?

Any and all input to these questions will be greatly apprecciated
(spelling?). Thanks to all. This forum is AWSOME.

Paul Brackna
PB Jewelry Designs
PBJewelryDesigns.com


#2

Hi Paul,

I have used both torch and hot plate to do Kum Boo with Argentium.
(I spell it Kum after discussing it with Komelia Okim, who brought
the technique to the U.S. From Korea). I learned from Celie Fago’s
book, and demonstrations by Komelia Okim and Paulette Werger.
Paulette and I both feel that there is a better bond with AS if it is
first annealed and pickled (one time is enough), and then scrubbed
with baking soda. I feel that I get a better bond on AS if the
surface has a bit of texture, but Paulette does not feel like it
makes a difference. The 1300 watt hot plate will be fine. As with SS,
soldering after kumboo tends to make the fold “fade” and alloy into
the silver. You can use this to get shades of color to make an
interesting design, or use thicker gold, or make sure that the gold
application is after all soldering.

Cynthia Eid
http://www.cynthiaeid.com


#3

I prefer to use a hot plate with a calrod burner. I prefer the
calrod to a flat surface, as most of my work is domed. On a flat
burner the piece rocks around and is difficult to work with. With the
calrod burner, I can put the piece between the coils, where it is
held securely, and is easier to work. If I am working on a flat
piece,
I merely lay a piece of stainless steel over the calrod unit.

Alma Rands


#4

cast iron… hmm, I personally avoid iron, in all forms, anywhere
near fine silver and even low karat golds ( 14-18). I don’t use
anything but stainless, tungsten, titanium, tantalum and copper
studio tools and am ultra careful when something is ferrous but its
use is unavoidable to contain any dust or particles, etc. generated
if the task involves abrasion of any kind… Iron is an insidious
contaminant particularly when working silvers. Unless the iron
itself is used as a part of the design or as an alternative, and
intentionally used metal I try to avoid anything containing it. One
time I alloyed a quantity of gold- I used the same crucible I always
used for 22karat golds, the same charcoal and ammonium sulphate
refining powder I blend, but the gold came out so incredibly tough
that it took more than 20 minutes to anneal to a half-hard state,
never acheiving dead soft temper, and was almost resistant to
rolling. I wanted to find out what happened since I keep an
unbelievably clean and over-the-top organized studio. and am truly
concious of ferrous metals entering the space- I had taught a class
a few weeks before and all the gold sweeps and filings were in the
batch I was processing. I used a magnet over the waste as always,
and it extracted a bit of a saw blade. All I could presume was that
the magnet missed some teeth off of the blade(s) that ruined the
whole pour. I remelted it and made grain, which went directly into
aqua regia. After a wait all the impurities dissolved out of the
gold, and I had to start again…I learned my lesson. and lost most of
the day’s work time. A friend and colleague that recently passed
away, DX Ross, shared the same philosophy about iron contaminants in
the studio -with equal vigilance so I knew I was neither alone nor
over reacting.!

I would, at least, put a barrier between the cast iron and your work,
even though you aren’t soldering on it, why risk contamination? it
can be as simple as a sheet of parchment or transfer (graphite) paper
taped down so it doesn’t shift when you are burnishing… otherwise I
would look for a glass topped hot plate at a garage sale, or thrift
store if you must use an electric hotplate. I have a sheet of
stainless steel, about a quarter of an inch thick, and keep it on a
tripod over an alcohol lamp to heat the surface, the grate on the
tripod acts as a diffuser for the heat…It works well, is
multi-purpose (for truing bezels, straightening or flattening soft
metals, etc.) and saves power. RER


#5

Several people have mentioned using stainless steel sheet over a heat
source to act as a flat hot surface. Stainless is a crappy thermal
conductor it will be very uneven in temperature and slow to react to
temperature changes. Try bronze or brass, copper or if possible
silver as it is the best thermal conductor there is and you will get
much more even heat with a faster heat up time.

James Binnion
@James_Binnion
James Binnion Metal Arts


360-756-6550


#6

I have a hot plate from a science lab from a high school sale of
equipment. It is a steel square slab with a dial but no temps. How
would I calibrate that, other than by guess?

Susan
www.ThorntonStudioJewelry.com


#7

Hi Susan,

When I took a class with Celie Fago she used a toothpick, if it
charred the toothpick (made the tip look burnt) it was the right
temperature. She also suggested using a wood-stove thermometer. Hope
this helps.

Linda Reboh
www.YourCosmicCreations.com


#8

Good point, Jim!

Several people have mentioned using stainless steel sheet over a
heat source to act as a flat hot surface. Stainless is a crappy
thermal conductor it will be very uneven in temperature and slow to
react to temperature changes. Try bronze or brass, copper or if
possible silver as it is the best thermal conductor there is and
you will get much more even heat with a faster heat up time. 

I like to use nugold/bronze/red brass or yellow brass. These conduct
heat better than stainless, are less expensive than silver, and don’t
flake off black oxide flakes onto your work the way that copper does.

Cynthia Eid
http://www.cynthiaeid.com


#9

Hi Linda,

When I took a class with Celie Fago she used a toothpick, if it
charred the toothpick (made the tip look burnt) it was the right
temperature. She also suggested using a wood-stove thermometer. 

Everything i’ve read says to heat the hot plate to the point when a
wooden chopstick chars. the toothpick sounds easier.

Joan


#10
One time I alloyed a quantity of gold- I used the same crucible I
always used for 22karat golds, the same charcoal and ammonium
sulphate refining powder I blend, but the gold came out so
incredibly tough 

It’s not a bug, it’s a feature…

If you managed to create rock-hard 22K gold, then you were onto
something and it is a crying shame you were in such a hurry to throw
it into aqua regia. I’d say, instead of regarding it as the waste of
a morning, you should have asked yourself if it was a "Eureka"
moment. Now, we’ll never know, unless you can re-create the
conditions and get the result analyzed.

Noel