This likely is a stupid question, but I have no other venue to ask
such stupid questions I have been pondering Mokume Gane for some
time now. I really don’t want to just buy a piece from Reactive
Metals because… well, my joy comes from playing with techniques. I
have a day job. I don’t have to make this work commercially. So,
looking at the options… soldering smaller pieces and running that
through the mill (is that really Mokume Gane?) or trying to do the
kiln bonding thing… I had an idea. We know we can diffusion bond
24K gold and fine silver on a hot plate (Keum boo) … so could I
start with a thin (as thin as I can roll it) piece of fine
silver, depletion bond a sheet of 24K Keum Boo foil on that,
depletion bond a piece of the fine sheet on that, repeat, repeat …
etc. Run the whole thing through the rolling mill… and go from
there? At some point will the whole thing fall apart? I am assuming
if you can depletion bond a piece of 24K to a fine base… you can
then drop a piece of fine on top of that and bond it??? Sounds too
simple doesn’t it? I know the resultant piece would have THIN layers
of gold and one would have to be careful when developing the pattern.
But… do you think it would work? I am thinking a sheet of thin fine
silver won’t bond to the bottom gold film like the Keum Boo foil will
bond to the lower fine base… so could this be done with successive
layers of foil - gold, silver, gold, silver, etc)… is fine silver
foil available? Is silver malliable enough to beaten that thin…
like you would make gold leaf? Opinions are welcome. If figure if it
was that easy… someone would be doing it
I expect Jim Binnion to hop in here at any moment with the
definitive answer, but from what I know, you could do such a thing,
but why you would is an open question. The layers would be so thin
that the gold in the earlier layers would diffuse to nothing as you
worked to bond the later layers. Essentially what you’d get would be
a silver billet with very faint, fuzzy goldish stripes. Depending on
where you get it, Kum-Boo foil is in the neighborhood of .0003"
thick. Which is to say “damned thin”. Even doing normal kum-boo on a
hot plate several times will let the earlier layers diffuse to the
point where they’re visibly fainter than the later layers.
You can (and I have) make fine silver foils in equivalent
thicknesses. Not especially hard, as long as you have a rolling
mill.
With luck and experimentation, you could probably pull it off.
Whether the results would be anything worth the trouble is another
question.
From the standpoint of is it remotely possible than I would say yes
but from a practical point of view I think you are wasting your time.
Diffusion is mostly driven by temperature and you are going to be way
too low in temperature for any significant amount to occur.
Thanks for the answer… I have a follow up… hypothetical question.
We know diffusion can occur at relatively low temps… keum boo. James
is the expert at thicker pieces at higher temps. So… is there a
temperature time relationship? James I know you have worked hard
perfecting what you do… I am not trivializing your accomplishments.
I’m just asking questions. I understand the issues with successive
diffusion of layers. So, my question really is hypothetical… Could
I lay a piece of 24K on a piece of fine silver at room temp
(burnished down)… and would it eventually diffuse? Obviously temp
is very important… and the question has no practical or commercial
implications. Is there a threshold temp one has to reach to excite
the atoms enough… or is it a time thing? Just an inquiring mind
seeking answers.
That’s a neat idea, but I think it may not work well. Charles
Lewton-Brain wrote some thoughts on Keum Boo :
and posited that it works by gas diffusion through the thin gold
foil. Once the thick silver sheet is thrown on top the bond may be
quite poor, if he was correct about the mechanism. You could do thin
foil for both, but you will be at it forever, and the resultant
pattern with be super tight.
The solder method works ok, if you don’t have access to a kiln, but
the true diffusion methods provide a superior billet.
So, my question really is hypothetical... Could I lay a piece of
24K on a piece of fine silver at room temp (burnished down)... and
would it eventually diffuse? Obviously temp is very important.. and
the question has no practical or commercial implications.
Probably not at room temperature, but if it did the time would be
ridiculous like thousands of years.
Is there a threshold temp one has to reach to excite the atoms
enough... or is it a time thing? Just an inquiring mind seeking
answers.
The temperature vs time diffusion relationship is very non linear.
The cited minimum diffusion temperature is 50 % of the melting point
of the alloy in degrees K. But to develop a good bond might take days
or more at that temp. As to what is a good enough bond and how much
diffusion that requires there are so many variables that it is not
really something you can give a general rule of thumb to.
Ask an archaeologist. Silver and gold items that have lain together
for a few thousands years will attach to each other. Interestingly
stained glass panels in windows that are several hundred years old
will be thicker at the bottom due to the glass (actually a
super-cooled fluid) flowing very slowly.
Thanks James! Isn’t it amazing what folks can do with limited
resources. I mean, you have worked hard to reproduce results the
"ancients" did with limited technology. I guess if you devote your
entire life to doing one thing (and have good teachers)… you get
good at it. Do we know how they made mokume gane… had to be in a
forge?? But… how did they keep the temp up for so long? I have been
following the "torch’ thread having a torch fetish myself… right
now I am playing with blowpipe soldering… with limited success. The
traditional techniques just leave me spellbound… What they could
do with so little. I like “toys” as we all do… but you have to have
a lot of respect for for folks who can make such beautiful things
with virtually no tools.
Isn't it amazing what folks can do with limited resources. I mean,
you have worked hard to reproduce results the "ancients" did with
limited technology. I guess if you devote your entire life to doing
one thing (and have good teachers).. you get good at it.
Good is an understatement. The finest decorative and functional
metalwork ever done was from the master sword smiths and armorers of
the Edo period in Japan. The work of the likes of Faberge, Tiffany,
LaLique and Cartier are close but I still believe the marvelous tsuba
and other sword furniture from the Japanese smiths are superior.
Do we know how they made mokume gane.. had to be in a forge?? But..
how did they keep the temp up for so long?
The method used by the Japanese smiths of old involved bringing one
or more of the alloys in the stack to a point just above the solidus
but below the liquidus of the alloy. This meant that there was some
amount of liquid metal that in effect soldered or brazed the layers
together but the alloy still had enough solid metal to hold its
shape, very tricky to do. Much faster than the electric kiln method
that holds the metals at a lower temperature for a much longer
period of time.
Probably not at room temperature, but if it did the time would be
ridiculous like thousands of years.
So the practical answer would be “no”
The temperature vs time diffusion relationship is very non linear.
The cited minimum diffusion temperature is 50 % of the melting
point of the alloy in degrees K. But to develop a good bond might
take days or more at that temp. As to what is a good enough bond
and how much diffusion that requires there are so many variables
that it is not really something you can give a general rule of
thumb to.
I’ll admit that I’m a noob at Mokume Gane, however I have done a
similar process with ferrous metals, called pattern welding.
Reading Fergusons book on the subject isn’t too far removed to the
process I currently perform.
One notable exception is the lack of flux used in Mokume Gane. When
welding ferrous metals flux is “sooooo” important, otherwise it will
produce a substandard piece.
Is it simply optional to use fluxes with Mokume Gane?
I used to pass along that old story too, but I don’t think that old
story about glass flowing downwards over the centuries is really
true. I seem to recall a thread on that subject some years ago and it
was pretty well debunked and I’m sorry I can’t cite chapter and
verse. Vague recollection that Ian Wright might have been part of
that exchange.
Anyway - any glass from long-enough ago for that phenomenon to have
occurred would not have been made uniform enough in thickness for
any such flow to be detectable or significant in comparison to the
already existing irregularities built into the glass as it came from
the manufacturers. Sheets were made by blowing cylinders which were
then cut down along one side while still soft and then opened out and
laid flat. Or maybe poured onto a surface to cool in place but you’d
need a perfect flat and level surface and also perfect uniform flow
and cooling conditions to get anywhere near uniform thickness. Glass
flat enough for the so-called gravity-creep to have been noticeable
was not approached until mid 19th century. Float glass - not invented
until the 1950’s - came closer to flat - made by pouring molten glass
onto a pool of molten tin - a self-levelling surface - where the
glass would spread out and float like a layer of oil on top of water.
So, yes, centuries old glass is not uniformly thick, but it has
nothing to do with gravity.
Interestingly stained glass panels in windows that are several
hundred years old will be thicker at the bottom due to the glass
(actually a super-cooled fluid) flowing very slowly.
That glass is a liquid is a myth, actually. Glass making methods
from antiquity didn’t produce flat sheets, and they were placed with
the thickest part at the bottom for greater strength and longevity.
There are examples of ancient glass in the ancient frame where the
thick part is at the side or top where it was, accidentally set, and
has remained.
I'll admit that I'm a noob at Mokume Gane, however I have done a
similar process with ferrous metals, called pattern welding.
They are essentially the same, virtually any method used for pattern
welding ferrous materials can be used to do bond nonferrous metals.
Reading Fergusons book on the subject isn't too far removed to the
process I currently perform.
One notable exception is the lack of flux used in Mokume Gane.
When welding ferrous metals flux is "sooooo" important, otherwise
it will produce a substandard piece.
When flux is used in hammer (press,roll) welding ferrous materials
it is supposed to be driven out of the joint by the hammering. If you
use the same method to make mokume you will need flux to help keep
oxides from forming on the faying surfaces just like ferrous pattern
welding. The biggest difference in most pattern welding and making
mokume is that in pattern welding you are making a much simpler weld
as the difference in composition of the various iron and steel alloys
is miniscule. But in mokume the compositions of the alloys generally
are much more diverse. It is this diversity of materials that makes
mokume welds more difficult.
Is it simply optional to use fluxes with Mokume Gane?
Yes and no, in limited situations you can use flux but in others it
will interfere with the bonding.
I have been pondering Mokume Gane for some