Fine silver cloisonne wires and cracking

Jewelry Discussion
#21 
and yes..there can be a problem mixing leaded and unleaded enamels.
You have just been lucky. Speaking to the experts at Thompson
enamel, where unleaded enamel is manufactured, they advised me not
to use unleaded on the back as counter enamel if I am going to use
leaded on the front.

From Thompson Enamel’s WORKBOOK regarding using lead-free and
lead-bearing enamel, “Certainly, lead bearing can be applied to one
side of a form and lead free on the other side, if the expansions are
close.” In addition, “…if lead free is applied underneath, lead
bearing enamel can be fired on top (after firing the lead free)
within the same cloison.”

Regarding circular-type cracks, as I recall, Darty states that this
type of crack is due primarily to COE (expansion) incompatibilities
(metal vs. enamel -OR- enamel vs. enamel).

BTW, Thompson’s WORKBOOK has a chart of all of the COE’s, Fusion
Flow, and Dilatometric temperatures for each of their enamels. Very
helpful. Ellis, Helwig and Carpenter wrote the WORKBOOK and at $9.98
it’s jam-packed with enameling (not well edited, but
every sentence has value). Highly recommended for any enamellist.

Regards,
Jamie

1 Like
#22

Many years ago I studied with Margaret Seeler and she said that if
you put flux under the opaques there will be less chance of getting
pits. Been doing it that way ever since. I sift the flux and then
the color on top. All one firing.

I have never had the enamel bleed through the flux. Maybe I am
firing at a lower temperature since I do cloisonne most of the time
and don;t want those wires to sink. I usually fire to 1450. If’s a
hard color, I go a little higher, but not too much.

Donna

#23

Jamie is absolutely right. Lead bearing applied over lead free will
cause no problems. I have been doing this for years as recommended
by the Thompson Workbook.

Also, I am very careful to watch the COE (Expansion rates of my
enamels.

Thompson has a chart of the COE’s in their workbook. I write the COE
on each jar of enamel so that I don’t have to check the chart each
time.

For those using the Thompson enamels I join Jamie in recommending
the Workbook.

Alma Rands

1 Like