With regard to Iris Cohen's warning [OGD V6 #366, message 4, repeated as
message 8, I presume for emphasis] about cleaning pots in bleach, from my
background in Chemistry and Biophysics, as well as long personal experience, it is
nonsense! I have no idea where the idea of saturated calcium chloride
contaminating the pots comes from. Calcium chloride is a very soluble substance
and washes out of pots easily. I cannot conceive of any reason why it should
concentrate in the pots. Moreover, far from calcium being injurious to orchid
roots, it is an essential nutrient of plants, more likely to do damage by
its absence than by its presence. I suspect Iris' observation was based on
some other coincidental factor that insulted the roots of her orchids. Each
spring, when I repot my Catasetums, I have hundreds of pots to clean, and the
thought of dragging them into the kitchen and cauterizing them in our oven is
a prescription for divorce and hernias.
I have been cleaning my pots in bleach for over 20 years and my orchid
roots have never objected, nor can I figure out any rational basis for why
they should. I use a 1:10 dilution of pool chlorine [calcium hypochlorite], in
an 18 gal plastic tub, which holds more pots than our oven. Although the
chlorine kills all virus, fungi bacteria and algae within seconds, I leave the
pots in over night, which removes all traces of algae and turns pot-clinging
roots to jelly, easily washed out during rinsing by hose. I then leave the
pots to dry and air out another day, thereby removing all traces of chlorine,
which might conceivably be harmful, and voila, clean and reusable pots. If I
need to process several batches of pots in succession, I simply recharge the
previously used bath with a couple of quarts of fresh chlorine solution.
One key to success of the process is a pair of long handled stainless
steel "crucible tongs," which can be obtained from a chemical supply dealer.
As for the ability of chlorine to attack metal, I have been using the same
tongs for 20 years and nary a speck of corrosion. Likewise I find no evidence
for bleach corroding stainless steel cutting edges, hence it is a marvelous
dip for sterilizing cutting tools when taking precautions against virus
contamination. About 30 seconds of contact with a 1:10 dilution of pool chlorine
does the trick. If Chlorox is used, the equivalent dilution is 1:5.
I have intuitive reservations about using muriatic acid in place of
bleach. It does not destroy organic tissue with the efficiency of chlorine
bleach and it must be washed out much more thoroughly, lest traces remain in the
clay pots which really would discourage plant roots. Bert
Pressman
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