Manual Glass Kiln

Enameling
on Metal
Preparing the Copper
Enamels come in transparent or opaque. They can be
purchased directly from Thompson Enamel, P.O. Box 310,
Newport, Kentucky41072. Their LeadFree Enamels come
readytouse.Noenamelwashingisrequiredfortheseenam
-
els.
Startwithoneofthemanypre-shapedcopperformsavail
-
able, or shape and trim the copper to your own design.
1 Heat the copper on an enameling rack to about
1400°F/760°C to burn off oil or grease. Heat the
copper to just until smoke from oil or grease stops
coming offthe metaland its color has changed to a
purple-red-pale green iridescence that moves
across the copper. This indicates that the grease
hasvaporized.Do not fire the copper any longer than
this point. Otherwise excess fire scale will form,
making the next cleaning step difficult.
2 After the copper cools, brush any loose scale from
the copper. Usea brush or paper towel, being sure
thatyoudonotputanygreaseoroilontothecopper,
such as fingerprints. Clean the copper with a 3M
Scotch-Brite® pad. This pad does such a good job
that in most cases no further cleaning will be re
-
quired. Additional copper cleaning products are
availableintheThompsonEnamelCatalog,includ
-
ing Sparex No. 2.
Itisbesttocleanthecopperjustbeforeyoudecorateit.If
youwaittoolongtodecorateaftercleaning,thecoppercould
get dirty again.
Decorating the Copper
Counter Enameling
Most enameled pieces should be counter enameled on
the back side. This gives the piece a much more finished
look, it eliminates a great deal of fire-scale cleaning, and it
controls the chipping and cracking that can result from the
different rates of expansion and contraction in copper and
enamel after the enamel has been fired.
Counter or backing enamel, a mixture that gives a mot
-
tled effect, can be used for counter enameling. Or you can
useregularenamel.Counterenamelisappliedbythesifting
method described below.
When firing counter enamel, underfire it so that the fire
scale on the front of the piece isn’t too difficult to remove.
Youcanpurchaseamaskingpreparationfromyoursupplier
tohelp prevent firescale. Youmust placethe pieceon astilt
whenfiringthe other (front) sideofthepiece.Thestiltpre-
vents the back of the counter enameled piece from sticking
to the enameling rack.
Applying Enamels
Apply enamelover aclean sheetof paperso youcan pour
theexcessbackintothebottleforreuse.Transparentenam
-
els should be applied in several thin coats. Transparent
enamels can be mixed with fairly good results. If opaque
enamelsaremixed,however,agrainyeffectresults.Thetwo
basic methods of applying enamels are sifting and spatula.
Sifting Enamel
SprayorbrushThompsonholdingagentontothecopper.
Thensifta1/32”layerofenamelontothe copper.Usea#60
meshsifter.Ifthecoatistoothin,youcaneasilyaddanother
coat after firing. But a coat that is too thick will bubble and
crack. The enamel must dry completely before firing.
Spatula or Inlaid Method
You can use this method to decorate a small area with
manydifferentcolors.UsingadilutedsolutionofThompson
holding agent, dampen the enamels just to the saturation
point, and maintain this moisture while working with the
enamels. Apply the enamels onto the copper with a small
spatula, and spread them out with a spreader to a coat of
about 1/32” thick. Lines of contact can be formed by the
spatula blade. Then spray the enamels with the holding
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