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Granulation without a backsheet


#1

Hi everybody

Sometime in the future, I would like to try granulation without a
backsheet. I have a book where the author uses mica sheets to protect
the spheres from melting while in the kiln. Wood working suppliers
sell sheets of mica, but it is used to make lamp shades…is this
the same? If not, does anyone know where I can get sheet mica to use
as a heat insulator? Is there an alternative to mica?

Thanks
Kim Starbard
http://www.kimstarbarddesigns.com


#2

Kim

Try these guys, when I was in their shop they had some very large
pieces for sale and I don’t recall the prices being that much.

The Quartz Source
503 Nashua St. 101A
Milford, NH 03055
603 673-0481

I can get Mica here in Colorado, but no where near as large as the
sheets they had, they were about the size of dinner plates and very
solid.

Terry


#3

I tried the thin mica sheet used in enameling. It swells up when
torched and the granulation overheats. There is an alternative that
works. William Haendel, in his 1961 paper on granulation, observed
that granulation designs were pre-fabricated. Although he could only
speculate about the granulation techniques he studied in museums
pieces, in his own granulation work he used steel sheet. I can
confirm that fine silver granules, plated with copper, will “eutectic
solder” together on steel sheet. When cooled, the granule design as a
unit will release from the steel sheet. Without adding more copper,
the “pre-fabricated” granule unit will “eutectic solder” to fine
silver sheet (using a torch, not a kiln). You do not pre-heat the
fine silver sheet. You only heat the granules until you see a flash.

I think using (non-galvanized) steel sheet not only works as a heat
sink to prevent the granules from collapse, but also makes a more
efficient use of the copper. Only a small amount of copper is left by
the time the granule unit is placed on the fine silver sheet (using
only glue and flux), and, after “eutectic soldering” this second
time, all of the copper is absorbed.

I have not tried gold/copper granulation on steel sheet but I believe
Haendel has. The exciting part for me is that Argentium sterling
granules can be pre-fabricated on steel sheet just by fusing (no
copper added). By pre-fabricating designs, it is easier to fuse
granules to a vertical or curved surface without risk of granules
drifting out of place. The pre-fabricated units are not structurally
sound until fused (or granulated) ontoa back piece. You can bend them
to fit up to a point. I have just completed an 18-gauge fused
Argentium sterling bangle bracelet with pre-fabricated fused
Argentium granules. A photo of it is

http://www.psi-design.com/granbangle.jpg

Hope this helps.

Nancy
www.psi-design.com


#4

Nancy,

Thanks for the info on pre-fabricating granules on steel sheet. Could
you please follow up with a couple more bits of info? How do you set
up the fusing process? Do you place the steel sheet on a charcoal
block, brick, or a tabletop kiln? Also, what is the thickness of the
sheet.

Bonnie Cooper


#5

Bonnie,

This is the fusing process I use for Argentium Sterling granules.
The steel sheet is from the hardware store and in the thinnest gauge
I could buy so that it could be cut with shears. The sheet is
approximately 12" X 24" and is about 1.5mm thick, if I recall
correctly about 22-gauge in steel sheet measurements. This steel
sheet is called “welding sheet” because it is not galvanized.

Cut 1 1/2" X 1 1/2" squares of steel sheet. Glue one granule unit
design to each square. As each design unit is done, place it on an
old (level) solderite pad until you have 4-6 squares. Allow to dry.
Darken the room so you can see the fusing. Use a small torch flame.
Fire each square until the granules are red hot (the steel sheet
also will be red hot) and you can see a small amount of liquid silver
on the tops of the granules. Move the flame across the granules. Hold
the heat for a second or two at this high heat (this might vary
depending on the torch). After firing, move the square to a cold
steel block. When the steel sheet cools, the granule unit releases
from the sheet. When all are fired and cooled, check each design
unit to make sure the fuse is solid. With magnification, you want to
see a small bridge of metal fuse between each touching granule (and
the wire, if any). If you cannot see this bridge, wet with the glue
mixture and re-fire the design right away. Try to avoid over-firing
because you will lose granule definition. Do not pickle until after
all the design units have been fused to a back piece. Just before
final placement, lightly sand the underside of the granule unit with
600-grit sandpaper and more aggressively sand the surface of the back
piece with 400-grit paper. If the back piece is thicker than
26-gauge, cut a steel sheet back piece for the back piece to prevent
slumping or overheating. For example, on the 18-gauge (1/4" wide)
bracelet, I cut a 1" strip of steel sheet to conform to the inside of
the bracelet.

After each use, clean the steel sheet squares with a steel wire
brush on the flex-shaft and store in a plastic bag to prevent rust.

I hope this answers your questions.

Nancy
www.psi-design.com