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Burned spots on mokume gane billets


#1

Hello

I am new to this forum and am in need of advise. I have been
attempting to produce Mokume Gane for about 6 weeks. I have read
everything I could find about the process, Binnion, Midgett,
Ferguson, Lawton-Brain, and many others (some more confusing than
helpful). I have a fairly complete blacksmith shop at home that I
have been working with for about 2 yrs. I am retired and it helps
keep me out of trouble. I stumbled on Mokume Gane while looking into
Damascus steel. It got my attention and now I am hooked.

My problem. I attempted to produce my first billets with a gas fired
forge. Having no experience the results were predictable. Now have
an older glass annealing kiln. It fires pretty constantly at 1500
±10 deg. I am using torque plates, stainless wrap, and charcoal. I
stack copper, brass, and nickel silver in 24 ga. 18 layers high. I go
through the same cleaning procedure each time, being extremely
careful not to decontaminate the surfaces. I have produced 4 billets
so far. After the billet is cooled I cut it into 1/4" slices clean
the edges and check under a 30x microscope. 2 billets are fine (at
least for me to experiment on) but the other 2 have what appear to
be melted/burned spots in the brass layers. All of the billets were
heated in the same way for the same amount of time (10 hrs.) Any
suggestions, advice, questions?

Gerry


#2

Hi Gerry,

By burned, do you mean melted - do the metals look like they have
"muddied" or a layer has partially disappeared?

Could be temperature in the kiln (have you verified with a separate
pyrometer?), could be different alloys (all materials from the same
supplier?), and could be some form of contamination. Without knowing
your cleaning process, it’s hard to say. Doing some cleaning
research, we noticed many things that seem to clean will also leave a
film.

As far as it occurring on 50% of your billets, it may be on the other
two, but you might not be noticing it on the slices you’ve made.

Hmmnnn, lots here, but I think that it can be solved with more info
from you, and all of the helpful folks on Orchid.

Chris
Chris Ploof Studio
508.886.6200 EST
www.ChrisPloof.com


#3

Thank you both for the input. The copper and brass I used came from
our local hardware store, prepackaged in cellophane, with no info
about composition. Mistake #1. The kiln has no controls so I checked
the temp with my own pyrometer. The kiln is an older drop front unit.
After a 1hr. heat with an empty kiln it read a steady 1505. This
pyrometer has not been calibrated. (how does one go about calibrating
a pyrometer?)

To prep the metal I use 400 wet paper until water sheets and then
dry with a lint free cloth. Then I rinse with acetone. I wear rubber
gloves during the entire process, the gloves are only used for this
purpose.

The burns resemble cinders and leave a small void. The void varies
in size anywhere from a pin point to a pencil lead. Only in the
brass which makes the comment from Celeste about burning the tin a
distinct possibility.

I have just ordered copper and brass sheets from a known source that
provides composition info. My wife says that I suffer from terminal
curiosity, so I will not be giving up. As soon as I get consistent
results I want to start with precious metals.

Gerry


#4
The burns resemble cinders and leave a small void. The void varies
in size anywhere from a pin point to a pencil lead. Only in the
brass which makes the comment from Celeste about burning the tin a
distinct possibility. 

Some brasses also include lead in the alloy, which improves
machinability or someting. I don’t know, but wonder if you’ve got a
leaded brass, and the lead is causing the trouble… Just a guess…

Peter