[meteorite-list] Re:Silica Gel Drying

From: FERNLEA4_at_aol.com <FERNLEA4_at_meteoritecentral.com>
Date: Thu Apr 22 09:49:02 2004
Message-ID: <11b.4b7450b.28dcac20_at_aol.com>


silica gel desiccant contains thousands of inter-connected microscopic pores,
giving a relatively huge surface area that wicks up water vapour through
absorption and capilliary action. It can hold up to 40% of it's weight as
water vapour.
When saturated, I can't help thinking that re-charging in a microwave is
going to heat the desiccant beads/granules far too rapidly and harshly, and
probably result in the bursting of those microscopic pores that you need to
preserve intact.
A slowly rising heat in an oven would be best ....allowing the trapped
moisture to evaporate in it's own time, and at it's own pace. Start by
warming it gently in an oven, then slowly ramp up the heat to about 80 - 90C
(190F) which can be maintained over a period of an hour (or more for thicker
layers) to drive off the trapped moisture. There's little reason to increase
the temperature above boiling point, as re-charging is never going to be 100%
efficient anyway.
One thing that's often forgotten during the re-charging process is that after
heating, the desiccant must be allowed to cool in an AIRTIGHT container,
otherwise it'll be part spent before you even get to use it again.

Rob Elliott
Fernlea Meteorites,
The Wynd,
Off Dickson Lane,
Milton of Balgonie,
Fife. KY7 6PY
United Kingdom
Tel: +44-(0)1592-751563
Fax: +44-(0)1592-751991
Email: fernlea4_at_aol.com
Received on Fri 21 Sep 2001 10:43:44 AM PDT

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