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Enamel back setting


#1

Hi Everyone,

I am new to this forum as a participant.

I am having a problem with setting an enamel from the back. After
the enamel is done, I make a bezel for it, I solder it to a sheet and
I cut out a space which is slightly smaller than my enamel. It’s like
a bezel for a stone, the only difference being that the prongs are on
the back on the piece. I then saw most of the bezel away, keeping 6
prongs. I keep those small - they are 1.5 mm wide and 3.5 mm long.
Today, the enamel chipped during setting, so I started all over and
the second time the enamel chipped again. I do not see a solution.
Can someone please help?

Kind regards,
Alicia Webb


#2
Today, the enamel chipped during setting, so I started all over
and the second time the enamel chipped again. I do not see a
solution. 

What you are doing is no different from the problems posed by prong
setting fragile stones, even though your prongs are at the back. The
key to most good prong setting is the seat and the preparation of the
prong. For the seat, first be sure the opening in the front sheet is
beveled appropriately to fit the surface of the enamel, so it’s not a
sharp edge in contact, but rather decent surface contact. Then you
need to fit the prongs. If you think for a moment what happens when
you bend a piece of metal, you realize the outside surface of the
metal stretches, while the inner surface compresses. The outside,
while stretching, sometimes gets an orange peel look, but otherwise,
unless it cracks, isn’t important. But the inside, when it
compresses, well, the metal has to go somewhere. It bulges inwards
toward your stone, or your enamel. What this does is to make the
prong contact the metal down low on the prong before you’ve bent the
prong all the way. Further bending can create fairly high and
damaging pressures at the point, even though the prong might have
started out not a tight fit to the stone/enamel, and isn’t yet
"down". The key is to shape the inner surface of the prong so that it
takes this compression into account, as well as controlling where the
prong bends, and when. Visualize what the prong would look like if
fully set and finished, how it would be shaped on the inside. Then
imagine what it would look like if you then pulled it back. You’d
see a hollow sort of space there. So before bending the prong, use a
bur (ball bur, etc) to hollow out the inner surface of the prong a
bit, especially a bit near the bottom where it will first contact the
stone/enamel. Then thin the prong’s end, sides and back a bit. This
allows you to control where the prong bends. Otherwise all the
bending is as close to the base of the prong as possible, and then
the enamel or stone will be forced to act as a fulcrum for the prong.
The aim here is to shape the prong so that, if you were to push it
over without the enamel or stone in place, it would still end up as
the correct shape. Done this way, you don’t end up with this fulcrum
point of pressure halfway down the prong’s inside. That’s likely
what’s chipping your enamel. What you want is for the prong to gently
conform to the enamel without pressure as you bend it, becoming fully
tight only at the end.

Needless to say, this takes some practice in judging just how to
shape the prong so it will do this. But try a couple test prongs.
Make one of your bezel preshapes, don’t bother to pierce the opening,
but cut the bezel away to leave as many prongs as you can. Use them
just bending over air to practice getting them to bend so as to reach
the correct final shape just from the setting tools pressure, without
needing the enamel or stone there to act as a fulcrum.

One other little trick. When you hollow out the prong, use a bur
that is a smaller/tighter diameter than the stone or enamel surface.
This way, as the prong contacts the piece, it first contacts just
with it’s edges, which exert less pressure, and can deform slightly,
flaring as you bend further, without putting lots of pressure on the
piece, while still letting you get the prong down flush to the
surface of the piece. Don’t hollow it out too much, as you don’t want
to make it deceptively weaker than it looks. Just enough so the
edges will contact first, not the whole inner surface of the prong.

You should also consider whether some of the problem might be that
your enamel is especially prone to cracking due to stresses in the
glass. Are you counter-enameling the piece? Do you perhaps need to
let the enamel cool more slowly after the final firing to let the
glass anneal a bit? Any other reason the enamel might be unusually
fragile?

Hope that helps.
Peter Rowe


#3

Think of the enamel as a delicate stone and try marking the bends of
the tabs and doing the bending when the enamel is not in place. Then
open them just enough to slip the enamel in and close them gently
until they just touch the glass.

Because this would result in a loose setting with the enamel piece
probably rattling around a bit, I am under the impression that in the
enameling world we might actually go ahead and use a 2-part epoxy
(like PC7, available in hardware stores) to secure it when using a
tab or prong setting. The point, of course, is that you cannot
tighten the tabs and prongs on glass like you can on a stone. (And
those who really don’t ever want to use epoxy probably don’t use tabs
and prong settings? I hope I’m not getting a glue war going here.)

And then as a last thought, you might also like to visit
grainsofglass.ning.com where everyone is an enamel artist and you
can post pictures of your piece and they might be able to give you
tips on how to make the edges less prone to chipping, in case that is
part of the problem.

good luck, vera


#4

Alicia- This is a good time to use an old skill.

In the old days when we set really fragile cameos and the like from
the back, we never put pressure directly on the stone. No prongs
needed. Just have the front part like you described.

Then roll out a thin flat wire of .999 or pure silver or 24 kt gold.
Shape and solder it to fit on the back of your enamel. Put the enamel
in place and the slide the soft metal rim behind it.

Then on the inside side of the bezel raise some beads up against the
soft metal rim to secure it against the enamel. Thus you are only
putting real pressure on the soft metal and not your enamel.

If this is confusing, email me off group and I can scan and send you
drawings.

Have fun and make lots of jewelry.
Jo Haemer
www.timothywgreen.com


#5

Alicia

When setting an enamel I like to give the edges as much protection as
possible. Therefore I bezel set it just as I would a cabochon. I
bring the bezel up just a smidgen over the edges of the enamel, and
burnish it down This gives full protection to the edges of the
enamel. I have never had any cracking of the enamel when I use this
method.

Sometimes I make a double sided cloisonne and want both sides
visible. In this case I make a bezel to fit the enamel, and solder a
square wire inside the bezel for the enamel to rest on. Then I set
the enamel on the square wire and burnish the bezel down over the
enamel fully enclosing and therefore protecting the sides of the
enamel.

There are may ways one can set an enamel. This happens to be my
favorite as I don’t have to worry about the enamel getting chipped or
cracked.

Alma


#6

Alicia,

Upload a photo to www.alihilanidesigns.com and I would be happy to
help you. Are you using fine silver for the bezel. Did you sand and
polish the girdle the outside edge of the enamel? How are you pushing
over the bezel? I find it is best to have a bit of height to the
enamel at the edge a girdle just like setting a stone. If the enamel
slopes down to meet the fine silver to a point and the fine silver is
soft it is very easy to crack.

Patsy Croft