Enamel thickness

Jewelry Discussion
1

All,

Many thinks for all of your wise, thoughtful answers to questions. I
have successfully etched some pieces now in sterling. Of course,
“success” is in the eye of the beholder. I can at least say the
design trasferred well and with a 10% solution of hot ferric
nitrate, I was able to reproduce the design well at least to the
naked eye.

However, I know you are supposed to use only fine silver, copper, or
gold, (palladium, platinum a problem?) but I practiced enamelling by
applying some transparent vitreous enamel to the etching. It turned
out somewhat unexpectedly in that the transparent blue was paler
than I thought it would be. I believe it was because the etching was
not quite deep enough to suit the enamel I was using. All part of
that “cognitive dissonance”. I have heard that sterling is not the
best choice. Probably a “stoopid” question, but how do those of you
enamellers out there determine how a transparent piece will look in
advance? Is it all trial and error? Do you practice at different
etching or engraving depths in relief or intaglio on different metals
with a given variety of enamel to gauge the look first before firing?
Have you seen variance between lots you recieve even of a given
enamel? I have years of experience in the polymer industry with
colorimeters, are they of any use,! or is the eye and experience the
gauge? For example, stopping the etching process occasionally to try
to measure the etching depth, and when your target depth is met, you
stop, clean and enamel?

I guess what I am asking is how do you determine the target depth
for a given set of metals and enamels, especially transparent
enamels?

Many thanks.
Seech

2

Your intuition is correct. I suggest that if you study enamels by
Faberge, you would realize that appearance of enamel is a combination
of many factors like background metal used; surface preparation like
etching, engraving, and etc; coat thickness, length of firing, and
others. Some general guidelines are possible, but experience is the
largest contributory factor.

This is actually what makes enameling an art, since there will be an
element of uniqueness in each and every piece.

Leonid Surpin

3

When I get a new batch of enamel I do a series of tests usually on
small sheet of copper that I’ve marked with a reference number. I
counter enamel, put a hard flux down and fire it, cover half the
flux with silver foil and apply the enamel. This gives me a basic
reference. I then divide the sheet by eye into two and apply a
second layer.

if you’re going to apply the enamel over an etched or engraved
surface I suggest you use a sheet of silver. Etch it to different
depths at different places - possibly by suspending he sheet in the
mordant and raising it every 10 minutes - and then do the same
series of enamel applications.

Part of the technique of enameling is this early preparation - every
batch of enamel you buy will differ slightly and it’s important to
do these tests so that you know what to expect.

Even so… there will always be surprises, disappointments and
delights.

Tony Konrath

4 
every batch of enamel you buy will differ slightly and it's
important to do these tests so that you know what to expect.

I didn’t reply earlier because I don’t qualify as an expert
enamelist, but I believe Tony approaches the real answer to the real
question. First off, as with ceramic glazes, enamels are usually a
more-or-less different color after they are fired than they look like
in the bottle. It’s really necessary to do tests - make up little
pieces of metal with test-firings of each enamel. Not only that, but
you should do them with and without underglaze and colors will be
different on different metals, too. Or oftentimes and unpredictably.
This is SOP in any enameling book or class.

And it’s not good practice to try to build up transparent enamel to
get a deeper color - use a deeper color to begin with and enamel
normally…

5

Hi, I have no personal experience with ferric nitrate, but I read
that it undercuts. Nitric acid, on the other hand, does not undercut.
This is important, esp. so if you work with Sterling, as it will
decrease the chance of pinging and cracking. When you etch a piece,
you need 0.6 mm depth - this is really the minimum. If you are
unsure, clean the piece and measure. As to your question of how I
anticipate how a piece will look, sometimes I just know what the
colours will do, but if I am not completely sure, I make a test.
Making tests gives you the opportunity to experiment. Do things which
are not supposed to work. You can always get rid of the enamel later
on if you want to save the metal. As for metal, my favourite is
copper. I think it is ideal for enamelling. If I use opaques, no one
will see the copper and if I use transparents, I use silver or gold
foils. Gold enamels great too and it is not a problem to use silver
or Sterling - you just need to be more careful - use counter enamel
and flux and put on thin layers. I never enamelled on Platinum but I
heard that it works. However, given the cost.

6

I test each batch of enamel when I receive it. As most of my work is
on fine silver, I test my transparent enamels by putting a dab on a
piece of mica and firing it. What you see on the mica is exactly what
you will get with that enamel on a piece of fine silver.

After firing the sample I attach it to a sheet of paper in the book
which I keep for samples. I have found that using clear scotch tape
to attach it does not alter the color. Next to each sample I write
the name and number of the enamel.

There are so many variables when enameling that it is difficult to
suggest proper depths for etching or engraving. As you work more with
your materials you will become familiar with the individual
characteristics of each enamel.

I keep meticulous notes on everything I do so that if I want to
achieve a certain effect, I have something to refer to. Even then,
the variables --size of the piece, length of time in the kiln,
temperature, thickness of the gauge with which I am working, all
enter into the equation.

As Tony Konrath points out there will always be surprises. I
consider enameling a joint venture involving the metal, the enamel,
the kiln and me.

Sometimes we all work in harmony. Sometimes there will be an
unexpected marvelous surprises. Failures can be held in check once
one learns the nature of the materials with which one is working.

Alma

7

Don’t forget that amazing effects can be made by layering different
colors over each other - but again it’s important to experiment and
do tests because blue over yellow doesn’t always give you green.
Molten enamels interact, fire at different temperatures and
sometimes just won’t fire together at all… they peel!

8 
I never enamelled on Platinum but I heard that it works. However,
given the cost.

I use a thin sheet of platinum as a backing for plique-a-jour. It
doesn’t adhere to the enamel and the object just pops right off…

9

Regarding enameling…

It's really necessary to do tests

Yes. Tests, plural. Per color.

I ran single tests on a number of opaque colors and liked the
results. I fired a detailed piece with a number of tested colors,
liked the results. Added another layer, fired again… !#$%^! Pink
turned tan, light purple turned brown…

Phooey, or a similar sentiment.

Neil A.

10 
As Tony Konrath points out there will always be surprises. I
consider enameling a joint venture involving the metal, the
enamel, the kiln and me.

A short trip to History will be helpful to appreciate complexity of
enameling.

Cartier was in strong competition with Faberge for the well-heelled
Russian Aristocrats. Enamel was Faberge strongest suit. His shop
could produce 137 shades of enamel. Combined with different
backgrounds, it gave him huge color palette. So Cartier hired the
best enamelists he could find trying to recreate Faberge colors.
Cartier was able to achieve wonderful colors, which in some instances
even exceeded Faberge in refinement, but he could not recreate exact
Faberge colors. The moral of the story is just let things happen and
enjoy the results.

Leonid Surpin

11

Neil,

If you are using Thompson enamels I recommend that you get their
workbook It is very inexpensive (around $10), and contains a wealth
of essential technical about their enamels.

When layering enamels it is essential to know the COE (coefficient
of expansion), of each of the enamels. You will find the expansion
rates, the fusion rates, etc. for each of their enamels, and this
will keep you from having undesirable results.

I write the COE on each jar of enamel so that I can refer to it
easily. This is particularly necessary to know if one is
layering enamels. It is all right to layer an enamel with a lower
COE, over one with a higher COE, and not the other way around or you
will get cracking. The workbook explains the different
characteristics of each of their fluxes (clear enamel),–experience
will tell you which you need for a certain project.

Pinks and light purples tend to turn brown if they are over-fired.
The same is especially true of the reds. Again, make tests under
different conditions, and keep notes on each test. Some enamels
mature at a relatively low temperature, others require a higher
temperature, (a matter of just a few degrees difference), or
sometimes they need a longer period of time in the kiln.

When making a piece which contains a number of different colors, it
is essential to know the characteristics of each. For example, as
reds burn out easily if over fired, I am careful to apply them toward
the end of my firing when the others have fully matured. Those that
mature slowly (the hard enamels), go on during the early firings.

Hope this will be helpful to you. By all means, do get
the Thompson workbook.

Alma Rands

12

‘When layering enamels it is essential to know the COE (coefficient
of expansion), of each of the enamels.’

Thompson makes good enamels, although some are difficult to work
with, for ex. I do not use the mauve transparent (2760). Fischer in
Pforzheim carries enamels made by Efco. They are a product for
hobbyists, but I think that they are great enamels - no problem with
difficult colours. However, I think that none of the lead free
enamels can ultimately compare with the lead-bearing Japanese
enamels. True, you need to be careful with them, but you need to be
careful anyway. You can use all of these enamels together. I never
bothered about checking out the COE of anything; I just fire and
find out what works and what does not.

13

Yes, I know. Some would like to take short cuts and skip a lot of
the work of testing enamels and watching their co-efficients of
expansions. However such a practice leads to many failures and sloppy
work, and gives enameling a bad reputation.

I am a strong advocate of testing all enamels prior to using them,
and making sure that they are compatible with each other. Also, it is
essential to make note of their coefficients of expansion to make
sure that there will be no problems down the road. It is most
disheartening to spend hours on a piece only to have cracks and
popping off of the enamel due to carelessness.

Only those just playing around with enamels as a hobby can afford to
take a chance with them and hope for the best.

Those who sell them need to make sure that their client is getting
an enamel that has been given the same respect and care that one
would give a precious gem.

My apologies if I sound self-righteous and preachy. However, I never
could understand why some think that enameling takes less study and
care than any other jewelry technique? Enameling is a fine art and
should be treated as such.

O.K. I am off my soap box. Thanks for bearing with me.

Alma

14

Ok I’ll bite. I understand the testing but how do you determine the
coe? I have the tables for the Thompson stuff but what about the
others? And what is hard enamel versus soft - is that related to the
softening temperature?. I’ve read Thompson’s work book and for every
definitive statement given there seems to be a but.

15

Alma,

Since the Japanese enamels that Alicia mentioned that she likes to
use don’t give about COE’s (co-efficients of expansion),
how would she go about testing them? Do people who use Japanese
enamels have a lot of failures because they don’t have this

just wondering, vera

16

Belinda,

The expansion rates (COE’) have all been determined for you and are
listed in the workbook on pages 3 & 4. for each enamel. They also
list the fusion flow, and dilatometic softening point. However, the
important numbers for enamelists are the expansion rates. People
working with glass need to be aware of the softening points and
fusion flows.

The numbers listed in the Thompson workbook are for the lead free
enamels. For the old discontinued lead bearing enamels, you will have
to ask Thompson to send you the chart with that

As I do a lot of layering of transparent enamels in order to achieve
certain effects,I find that it is essential to know the COE, so that
I will not be putting one with a high expansion over one with a low
expansion as to do so, invariably results in cracking, and even
popping off. Sometimes this will happen days after one has completed
the enamel…

Also, when I am working with colors having a high expansion rate, I
make sure that I am putting them over a flux that has an even higher
rate of expansion.

Regarding hard and soft enamels. This is indicated for each
flux–hard, medium, soft.so you don’t have to do any research on
that. Regarding the various colored enamels. Fortunately almost all
of the enamels fuse at the same temperature and length of time. So
you don’t have to concern yourself too much about it. There are a few
exceptions—one being the old lead bearing Amber. It takes longer to
fuse, so, when I use it on a piece that has a number of other colors,
I put the amber on early in the enameling process so that it fully
fuses, then work with the other colors.

Reds are notorious for burning out (turn ugly brown, or blackish).
These go on for the last firing.

Much of my work consists of commissioned large wall enamels. I can’t
afford to take a chance with these and have to be very careful about
the COE, and other factors.

I am just as careful with small jewelry items, as nothing is more
disappointing than putting in hours of work on a special cloisonne
enamel, only to find hairline cracks appearing just when one is
nearing completion of the piece.

If you run into any special problems or have questions not answered
in the Workbook, give Tom Ellis, or Bill Helwig at Thompson enamel a
call. They are the experts, and are always willing to answer
questions.

Alma Rands

17 
Some would like to take short cuts and skip a lot of the work of
testing enamels and watching their co-efficients of expansions.
However such a practice leads to many failures and sloppy work, and
gives enameling a bad reputation.

Wait a minute. I am a professional enamellist and goldsmith. There is
absolutely no sloppy work and my enamels have an excellent
reputation. What I said was that there should be tests. And there
should be failures, in the tests, so you learn something. To hell
with coefficients of expansion. They tell you something you need to
know in the beginning which experience will eventually take over. As
I said earlier, I often use many different enamels in one piece -
lead free as well as lead bearing ones and from different companies.
If I need to check the CoE’s of all those enamels, I can sit here all
day. Your post gives people the incorrect impression that it is
absolutely necessary to check CoEs, otherwise no decent work can be
done. For people who want to progress in enamelling, I am urging them
to forget about CoE’s, to buy some copper sheet and try things out
until they have it perfectly right. Granted, this takes a long time.
When you do this, you will see the relativity of CoE’s and you will
discover a lot of things. If you don’t, your work will remain
mediocre forever. One is, of course, completely free to make the one
billionth piece of cloisonne (c) - this is exactly the reason why so
many of those pieces look the same.

Cheers,
Leach

1 Like
18

Vera.

I have never worked with the Japanese enamels,so really can’t tell
you whether or not people using them have failures due to not having
access to the COE’s.

For about the Japanese enamels, I suggest you contact
Coral Schafer (Sp), at Enamelworks. Coral sells the Japanese enamels
and may have charts giving essential abut them. Coral
also makes extensive tests on everything that she sells, and
willingly shares this

Alma.

19

I use the Japanese enamels, and my understanding is that they are
formulated in such a way that their Coefficients of Expansion do not
vary much. I don’t give any thought to COE’s in layering my enamels,
and have had no issues. In general the Japanese colors are less
finicky, and also with fewer problems with reds and oranges turning
to brown as well.

It is important to note that because they contain lead ( and other
heavy metals) you must take proper safety precautions when using
them. These include wearing a respirator when sifting or grinding
them, and mopping the floor rather than vacuuming. Do not pour water
from grinding or washing enamels down the sink–instead leave it to
evaporate, and dispose of the dry residue in an appropriate
hazardous waste site.

There are many things to know about working with enamels that can
only be learned through experience. Make color tests of each color
over copper, silver foil, silver foil with a layer of flux, and gold
foil, and with these as a guide, just start using them. There are no
short cuts–your technique will improve as you gain experience. I
think this goes for your challenge of depth of etch vs. intensity of
color. You will need to do testing, etching for various lengths of
time, producing cavities of different depths. Keep careful notes!
Then fill all the cavities with your enamel, and thus determine the
length of time which produces the color that you prefer.

By the way, one can enamel on sterling silver. It has been done
successfully in many commercial applications. It is simply easier to
enamel on fine silver. Some colors don’t work on sterling, and you
have to do tests to determine which ones.

Amy Roper Lyons

20

Alicia,

My sincere apologies if my comments offended you. In no way was I
referring to you or your work. I am sure that you are an excellent
enamelist and do professional work.

My comments were meant for those just starting out and who were
having problems with cracking and chipping of enamels.

You obviously have developed a keen knowledge of the characteristics
of the enamels with which you are working and have avoided so many of
the problems that those new to enameling encounter.

Again, please accept my apology if it seemed my remarks were
directed at you They certainly were not.

Alma