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Re:bleaching vs baking.

James Purchase wrote:

.....I like Paul's suggestion of baking the material in order to sterilize it.
The highest temperature possible in a domestic oven (around 500F) is not
likely to damage the chemical or physical properties of the Flourite, but it
should be more than enough to kill anything living in the gravel. Just make
sure that you choose a fine day to do it - you might want to keep the
windows open for ventilation.

But you can't bake any gravel which is coated with plastic...

My suggestion was to cook it in a crock pot for a day.  The long cooking
time is to insure that all of the gravel-fluorite mixture gets heated to
boiling.  I suppose that an oven at 350 degrees F would work, too.  It
might be a bit more smelly, as James suggested.

I have never cooked gravel.  Since I use local soil, I don't have any need
to save it.  I just wash out the dirt, pour about 5% bleach on the gravel,
let it sit for a day or two, rinse, drain, and dry.  While the gravel is
drying, I notice that the smell changes from an anaerobic mud sort of smell
to a "sulfurous" kind of smell, like that of a burning kitchen match.  My
hypothesis is that bacteria, introduced after the bleach is rinsed away,
have colonized the gravel and oxidized a number of reduced sulfur
compounds.  Since the bacteria are present, I can assume that the bleach is

Paul Krombholz, in dry central Mississippi