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Fractured Enamel


#1

Hello,

I’ve been having repeated fractures on my leaded enamels during the
last stage of transparent enamel application. A lot of it chips off.
Any suggestions?

Sheridan in Chicago


#2

Fracturing of the enamels can be caused by a number of things. Can
you give us some more What metal, and what gauge are
you using. What is the size of the piece you are working on? Are you
counterenameling?. Are you using flux under the colored enamel,and if
so, are you making sure that you are paying attention to the
coefficents of expansion. (higher goes under the lower). This is
particularly crucial if you are layering different shades of
transparents over one another. If you give us some specifics those
of us who enamel will be better able to diagnose the problem.

Alma


#3
I've been having repeated fractures on my leaded enamels during the
last stage of transparent enamel application. A lot of it chips
off. 

Hi Sheridan,

This could be caused in several ways…e.g. the enamel might be too
thick with too many layers, the enamelled undercoats may not be
compatible with the final transparent coat, the metal may be too
thin, the piece may not be counter-enamelled, perhaps the piece has
cooled too quickly from the iln. Without knowing all your procedures
it is hard to tell. If you can give some more perhaps I
could be more helpful.

Cheers, Jenny Gore, South Oz.


#4

Sheridan,

I've been having repeated fractures on my leaded enamels during
the last stage of transparent enamel application. A lot of it chips
off. Any suggestions? 

Some questions for you:

What kind of leaded enamels are you using? and what are their melting
points? Not all enamels are created equal.

Are you counter enamelling?

a. First?
b. last?
c. how thick is your enamel on the top of your piece?
d. is your counter enamel as thick as the enamel on the top?

Is your last layer of transparent enamel of like and kind (melting
point) as the rest of your enamel?

Jennifer Friedman
enamellist, jewelry artisan, ceremonial judaica
Ventura, CA
@jennifer_friedman


#5
repeated fractures on my leaded enamels during the last stage of
transparent enamel application

You didn’t say, but you are counter enamelling the pieces, right?
I’ve seen fracturing and flaking of enamel if the metal is not
counter enamelled or if the counter enamel is a great deal thinner
than the front enamel. At one workshop I took, the finished piece
was pulled from the kiln and immediately placed into a small
firebrick enclosure to moderated the speed of cooling and thus avoid
cracking.

Donna in VA


#6

What gauge fine silver or copper are you enameling on? I find that
if my counter enamel is not thick enough I tend to get fractures. Add
another coat of counter-enamel, bake, then reapply where it fractured
and chipped off. Hopefully this will remedy the problem.

Lisa Hawthorne
@Lisa_Hawthorne1


#7

often], it sounds as though it may be a tension issue. Are you back
enameling your pieces? How thick are the pieces that you are
enameling? If your piece is very thin there may be too much stress on
the enamel from the unenameled side. This can cause the enamel to
break away as the metal cools. You may need to counter enamel the
other side]. If it is not this then perhaps during the polishing
processes you are flexing the piece during handling.

Good luck Dennis


#8

Thank you all for your replies to my question re the fracturing of
my top coat on recent enamel work.

Alma asked:

Fracturing of the enamels can be caused by a number of things. Can
you give us some more What metal, and what gauge are
you using. What is the size of the piece you are working on? Are
you counterenameling?. Are you using flux under the colored
enamel,and if so, are you making sure that you are paying attention
to the coefficents of expansion. (higher goes under the lower).
This is particularly crucial if you are layering different shades
of transparents over one another. If you give us some specifics
those of us who enamel will be better able to diagnose the problem. 

I’m using 1" soft triangles of 24 ga. sterling with leaded enamel
and cloisonne wires. Yes, I counter enameled. Yes, I fluxedbefore
putting down my cloison wires and wet packing the enamels. No…I did
not remember to check the hardness of the enamels before laying them
on. Everything was going quite well (no pitting, no cracks, no
chipping, no color changes) until I attempted to “finish” the piece
with transparent flux. I didn’t want to add any more color so I chose
to bring up the height with leaded transparent. I stoned the work
before this last coat, washed thoroughly in distilled water and let
it dry before putting on the flux. The “chipping off” was over the
brick red opaque. The transparents in the other areas were fine.

Sheridan in Chicago


#9

Dear Sheridan,

I once had a commission to make a band ring (in 18k gold special
alloy for lead enamel) and the desired color was “lipstick red”. I
had infinite trouble trying to get opaque red to work – and that was
on gold, which I consider to be more friendly to enamel than silver.
I never could get the opaque red to work and I tried every type of
enamel in my arsenal. I don’t remember all of the things that went
wrong as it was many years ago and not a happy memory but I do
remember I could not create the ring as it was originally envisioned.
I never did work much with opaques, except black, as I was usually
enameling on gold and usually didn’t want to hide the metal so I
don’t know if the problems were particular to reds or if there would
be problems with other opaques also. I do think your problem has
something to do with the opaque red…

Good luck to you. Let us know what you figure out.

Janet


#10

Hi Sheridan. I’ll address your response one item at a time.

  1. It isnt the Hardness or softness of the enamel that causes
    problems. It is their COE (coefficent of expansion )rates. Hardness
    and softness, and COE’s are two different things. If you are working
    with Thompson enamels you can check with Thompson to find out the COE
    for each of the enamels you are working with. In fact, if you do not
    already have it, get their Workbook. It costs about $10.00 and is an
    invaluable source of

2). 24 gauge is very thin. for a triangle of 1" I use 18 gauge.

3). I avoid sterling, as even if you bring the fine silver to the
surface before beginning to enamel, you usually run into problems
around the 3rdor 4th firing. I much prefer fine silver to sterling,
as one does not have discoloration problems. Sometimes I use copper
covered with gold, or silver foil–depending on what I am making.

4). Regarding the flux you used as the final layer---- it may have
had a COE lower than that of the enamel below it.

Also,remember that the thickness of the counterenamel on the back
shouldbe equal to the amount of enamel you are applying to the face
of your piece.

To sum up, I would suggest you use a heavier gauge metal, and watch
those expansion rates, and the thickness of the counterenamel. Hope
this helps.

Alma


#11
I didn't want to add any more color so I chose to bring up the
height with leaded transparent.  

From the colors you’re using, they must be Thompson’s. There are
three varieties of flux, soft, medium and hard…which were you
using? Brick is one of the colors which can’t stand a lot of heat.

Donna in VA


#12

Hi Alma,

24 gauge is very thin. 

Your are implying that it is too thin to enamel.

In general, I would agree with you. However, I have been successful
in enameling gilding metal and copper at this gauge by first making
line folds in it. Consequently the cloisonnes or cells are integral
part of the piece and cannot be sheared off.

In addition I have enamelled 24 gauge sterling that I first “chased
in air”. The subsequent pits filled with “midnight blue” had no
spalling, although the flat surface did.

David


#13

Opaque red enamels have the highest melting temperature due to the
iron ingredient.

There are several problems that you’ll face. The first is the fact
that different suppliers use different ingredients and therefore
your temperatures may vary. To overcome that I make test (and keep
for future records) samples of each supplier’s enamel upon on
different karat gold surfaces.

It’s best to enamel onto 18kt gold but with experience 14kt gold can
also be used.

Another consideration is whether or not you use kiln or hand-firing
methods to melt your enamels. A direct flame during hand-firing,
will burn the enamels. So you may want to kiln fire your reds.

Finally…review all the steps of enameling process: make sure the
metal is clean and not pitted, shallow areas for enameling, grind
the enamels finely and wash thoroughly with distilled water.

If all else fails make an offering to your Deity of choice.

Good luck.
Kim.
www.kimericlilot.com


#14

Ah, using sterling, and a fine gauge for enamel as well. Have you
depletion gilded the sterling to bring the fine silver to the
surface? 24 ga. Is rather thin unless your pieces are very small. It
sounds like your enamel is too thick for the gauge of metal you’re
using, also if you didn’t bring the fine silver to the surface I
think fracturing could be expected.

Lisa

Lisa Hawthorne
@Lisa_Hawthorne1


#15

Hello All Who Answered

I appreciate the wisdom of you who helped me out with your analysis
of my fractured enamel problem. I heeded your advice and put on more
counter enamel coats. I then ground out the fractured opaque red
color, washed with distilled water (using a glass brush) and
reapplied the red. I also applied a very, very thin top coat of
transparent. I then fired it at 1450 for several minutes and
VIOLA…all 5 of the pieces are OK. Thank you

Sheridan