u7211aa at sunmail_lrz-muenchen.de (Michael Irlbeck) wrote:
>Date: Fri, 09 Jun 95 08:10:12 EDT
>Can someone please explain what Vermiculite is. I don't know this word
>and it would be easier to follow the discussion.
Vermiculite is a form of mica, probably mostly aluminum silicate, that
has microscopic amounts of water between the thin sheets. When baked,
it puffs up as the water is boiled out, and, as it cools, air gets in
to replace the water vapor. Chopped into tiny pieces, it makes for a
very high surface-area/volume material. Unfortunately, all that air
makes it float, when contact of all that surface with water is actually
needed for ion bonding.
It certainly is not clay, as was stated here earlier. Pumice (volcanic
SiO2) is often used in the same way, for it is very porous with lots of
surface area. It, too, unfortunately, floats.
Has anyone tried displacing the air under partial vacuum, and forcing
water into the voids? A "wetted" vermiculite could be a very nice
material for substrates. Extremely inert chemically, but providing huge
area for surface interactions. If no one has tried this, maybe I will,
and report back here. Maybe boiling, as with peat, is all the force
needed to get the water into the spaces between the leaves.