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Enamel shrinks from the edge


#1

Hello,

I am new to enamellin and having some problems. Quite often the
enamel shrinks from the edge of the copper I am enamelling. Also if I
use transparent enamels over flux or white the coloured enamel seems
to come away from the edge despote making sure I have covered the
edge. Also I sometimes get holes in the top coat so I can see the
flux underneath.

Thanks
Vicky


#2

Vicky, The enamel is not actually shrinking away from the edges of
the copper. Most likely it is burning out, leaving a black edge on
the copper. This must be filed away carefully after each firing.
Also, make the enamel thicker along the edges—just dust on extra
enamel along the edges using your tiny little sifter.

Regarding what you refer to as holes in the top coat revealing the
flux underneath. This is referred to as “breakthrough,” and is caused
by differences in the rates of expansion between the two enamels
being used.

I don’t know what brand of enamels you are using. I use Thompson,
and always check the expansion rates when layering enamels. In order
to avoid breakthrough, the enamel with the higher expansion rate goes
on the bottom.

Check the expansion rates of the fluxes you are using, and if you
are planning on using a top coat with a high expansion rate, be sure
to use a flux with an equal, or higher rate.

If you are using Thompson enamels, be sure to get the Thompson
workbook. It is very inexpensive and contains a wealth of information
about enamels. Also, it has a chart with all the expansion rates
listed. Hopes this helps.

Alma


#3

Well, you’ve just found out why enamelling is always a challenge
:-))

(1) your enamel should pull back from the exact edge of your copper.
You will then clean the edge up before applying and firing the next
coat.

(2) your second coat of transparent may not have the same COE as your
bottom layer.

(3) holes in the top coat can be caused by many things. Have you
sifted your enamels?

What heat are you using and what process are you using to heat the
enamel? You may find a lot of assistance in the Enamel Forum on
YahooGroups.com - you might want to check them out. You may also
want to invest in a good all-over enameling book - Linda Darty’s
comes to immediate mind although there are several others out there.
What you’re experiencing is common, but frustrating. Hang in there -
it gets better :-))

Sandi Graves, Beadin’ Up A Storm
Stormcloud Trading Co (Beadstorm)
http://www.beadstorm.com
Saint Paul, Minnesota USA
651-645-0343