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Vermiculite
Vermiculite is a mineral that is mined throughout the world.
Often sold as potting soil in garden shops, its industrial uses
range from insulation to absorbent packaging to filtration to
fireproofing. It's even used for fireproofing doors and safes
and for fading and aging "stonewashed" denim jeans.
From a glass perspective, vermiculite's refractory properties
make it ideal for use in the glass studio. Bead makers often
plunge hot beads into loose vermiculite as a way to slow down the
rate of temperature decrease. Loose vermiculite can also be
added to molds to increase strength and reduce the likelihood of
thermal shock.
Vermiculite can also be pressed and glued into board form (not
unlike pressed wood or particle board). Vermiculite boards,
which are most frequently marketed by a Danish company named Skamol,
can be used as dam material or as a kiln shelf.
From a health perspective, vermiculite is considered a nuisance
dust. Small particles can irritate the eyes or lungs, but
careful handling (and a dust mask and safety glasses) will eliminate
this concern. On some occasions in the past vermiculite
deposits in mines have been contaminated by adjacent asbestos
deposits, but this is relatively rare. Most vermiculite mines
are tested for asbestos and in most cases vermiculite is no more
risky than any other nuisance dust.
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Copyright 2005 Brad Walker.
All rights reserved.
This article is one of a series
on refractory materials for the kiln worker. Future tips will deal
with vermiculite board and with other refractory materials such as
mica, plaster, and various metals.
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