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mt. st. helens glaze formulas

updated sat 31 may 97


Michael McDowell on fri 2 may 97

Hi gang!

Somebody posted a request for glaze formulas using Mt. Saint Helens
volcanic ash. Mine are always in a state of change it seems, but I thought
I'd offer a few that I am using now.

Mt. St. Helens Herself (^9-^11with some reduction)

97 Mt. St. Helens Ash
3 Bentonite
100 Total

This glaze will not melt to a smooth coat in straight oxidation. It
requires the fluxing action of the iron in the ash when reduced in order to
melt. Very viscous, extremely thick coat still will not run. If reduced
early enough (maybe cone 018) this will be an all over coppery brown gloss
glaze. Reduction later in the fire will yield a black matrix with lots of
little coppery brown spots.

MSH Celedon (^10 reduction)

30 MSH (FFF)
21 Custer Spar
12.6 Silica
11.5 Talc
10.5 OM-4 Ball Clay
8.4 Calcined Kaolin
6 Whiting
100 Total

This glaze depends on the early reduction to develop celdon green. If your
firing schedule produces all over coppery brown with "MSH Herself", then
this will develop for you. Craze free on a low expansion body. If glaze is
spotty, refine your ash.

All Saints Red (^10, light reduction, possibly oxidation)

40 MSH
28 Silica
8 Calcined Kaolin
7 Talc
7 Bone Ash
5 Red Iron Oxide
5 OM-4 Ball Clay
4 Spodumene
104 Total

Have you ever been disappointed by an iron red glaze that looks great, but
is so heavily crazed that the pots lose their ring (all you hear is a thud
when you tap the rim with a stick)? Then try this one. I fire it along with
my celedon, but only on iron free clay body. It should work on most bodies
when there is not a heavy early reduction. Could actually be worth a try in
^10 electric firing.

By the way, there is a lot of testing behind these glazes, credit would be
appreciated, but I know how that goes...

Michael McDowell
Whatcom County, WA USA