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Enameled cab crack after setting


#1

I have read that a finished “jewel” can crack much later after
finishing successfully. I can’t imagine going to the expense and
spending the time to hand fabricate a setting and then have the
enameled cab crack after setting. Is there a time window during which
the cracking might be expected to occur? In other words, can one make
the enameled cab and wait a certain length of time, after which
cracking should not occur, and then make the setting?

J. S. Ellington
432-557-8785
http://www.jsellington.com


#2

I have not done much enameling for setting in a strip bezel pressed
down on the enamel cab. But I have read enough to know that the
enamel being glass fused to a metal. If you put it in a stressful
state sooner or later it will crack split or completely shatter.
Just as a small speck under a sheet of glass that is being cut can
cause the glass to crack in a wild manner and direction.

When you are using the bezel setter/rounder or what the tool of
choice is to fold the bezel over to hold the cab in place if you
press to hard on one side area and not enough some place else. Or if
you Go-rrilla it down all the way around to hold it in place. Since
the enamel layered and fused on the surface of the copper maybe
thicker or thinner as it was applied the stress will be unequal from
the bezel pressing on the fused enamel. The stresses that are set up
will cause a failure sooner or later.

Margaret Seeler suggests that each enameling blank should have a
1/32-inch flange around it.

From your other post. This would be the almost perfect solution. The
metals edge would provide one with the perfect uniform stable holding
platform. As long as you roll the bezel over with a steady pressure
around the edge the enamel shouldn’t be placed under any undue
strain.

The enamel shouldn’t crack from the bezel placing stress on top of
the fused glass. And if your enameled cab have been done properly
and cooled correctly. They will out last us all. Here are two very
good sources for info on enameling.

http://www.thompsonenamel.com
http://www.glass-on-metal.com

The ask the expert in the glass on metal site do respond in a timely
manner. And the catalog on line can answer alot of the newbies
questions on enameling 24/7 after all they wrote the book on
enameling as it were :slight_smile:

glen been there done that and scrapped it!


#3
I have read that a finished "jewel" can crack much later after
finishing successfully. In other words, can one make the enameled
cab and wait a certain length of time, after which cracking should
not occur, and then make the setting? 

I think the cracking can depend on many factors…thickness of
enamel on the surface being a major one. Is the counter enamel as
thick as the top surface, have any “extras” like lumps been added?
Could the piece have been bumped by something sharp? Could a little
"crunch" have happened at the bottom edge of the cab while rolling
the bezel? I have pieces which are 3 or 4 years old and never
cracked. I’ve never had any returned to me for cracking, either. I
think it’s a good idea to have the piece properly protected in your
design so that the edge isn’t too vulnerable…so maybe a flange
around your back plate.

Donna in VA


#4

I don’t know where you read that an enamel can crack much later
after finishing. If it was made correctly with attention to all the
technical details such as proper thickness of metal, counter
enameling, coe, etc. there should be no cracking down the line. In
all the years I have been enameling I have never had a problem.

I work with the old Thompson leaded enamels, but cannot speak for
other brands of enamels. You might inquire as to the kinds of enamels
which have been causing problems.

Alma


#5

I would like to say that there is a definite time window, I have had
things “ping” as long as a year after the final firing. I hope we
hear from some of the other enamelists about this!

Karen


#6
I have read that a finished "jewel" can crack much later after
finishing successfully. 

Alma has a really good point here. Tell us what gauge copper or fine
silver you are using as a base, are you doming, any surface
treatment such as rolled texture, what brand of enamels, leaded or
lead-free…are you combining the two, technique…stencils,
cloisonne, are you going from hot kiln to air-conditioned room,
removing the piece from the trivet before it’s completely cool,
clean your trivits (filing off dripped enamel) so the pieces don’t
stick, etc.

I used to do large wall pieces, mostly arquitectural or landscapes
with 15-20 firings and the only time I had any problem was when
Thompson replaced some of the leaded colors with lead-free. I had
major shattering off of enamel and learned later that you can do
leaded over lead-free but not the other way around.

Donna in VA


#7

Having one crack a year after setting means that it may be sold by
then! The idea of selling a piece with the potential for cracking
later makes me very uncomfortable. I too am eager to hear others
comments.

J. S. (Sue) Ellington
http://www.jsellington.com


#8

My question is regarding any cracks with any method. The question
is: If it will crack due to improper technique, is it likely happen
in a given time window. I realize that a bump or trauma to the piece
can crack it at any time, but I was wondering if cracks due to
improper original technique can show up or occur far into the future?

I have read (and in fact had one reply to this post who said one
cracked a year after being finished) that people have had enameled
jewels crack long after they were finished. Maybe this was due to a
blow to the jewel that happened unnoticed and that cracking due to
bad enameling technique was not the cause.

J. S. (Sue) Ellington
http://www.jsellington.com