|The following is reprinted with permission from the
Questions Department of the January 2003 issue of "Ceramics Monthly",
page 118. Copyright 2003 by The American Ceramic Society. All Rights
Reserved. Visit "Ceramics Monthly" at www.ceramicsmonthly.org.
||I am an elementary art teacher. I need to know what
can prevent mold from growing on the clay. I have a bucket lined
with two bags, and it is always covered. I have heard Epsom
salt is a better alternative than vinegar, but would like some
||I have been a potter for over 40 years now
and I always welcome that smell when I open a box of clay. It
means the clay has "aged" – enough time has
passed between the mixing of the clay and its use for bacteria
and mold to develop. This is a good thing, because mold and
bacteria contribute to the workability of the clay.
The way these by-products of the aging process contribute to
workability is by increasing the flocculation of the clay body.
This means that the clay particles will stay together better.
Handles and other attachments will stick on better and the clay
has less of a tendency to crack. The clay’s strength,
plasticity, and resistance to stress are improved. Some potters
even add some of their aged clay to freshly mixed batches to
get the new clay to produce bacteria and mold faster than it
would if left on its own.
My answer to your question is: Welcome that smell! Whenever
you smell it, it means that your job as a potter has just become
Some clay makers will occasionally add vinegar to clay to improve
its workability. However, if clay that has had vinegar added
is not used within a few weeks, then the smell can get to be
too much. I don’t recommend it at all, because if you
are trying to get rid of the smell, this will make it worse
in the long run. Epsom salts will not cause the strong odor
associated with vinegar, but will have the beneficial effect
of helping to flocculate the clay body. Keep in mind that clay
may contain bacteria anyway, and Epsom salts will not prevent
There are some individuals who are allergic to molds and mildew.
They should not be around clay to start with. If aged clay is
making anyone sick, and for some reason they have to be there,
I suggest using bleach to cut down the bacterial and mold activity.
This is not the best solution, because chlorine has its own
drawbacks. Perhaps a few drops of diluted bleach in the bucket
now and then might be a solution, but it might cause reactions
more than the mold or bacteria. I certainly would not use bleach
unless I absolutely had to.
In the end, my suggestion would be to get used to the moldy
smell. Or, do as most potters do – welcome it!
Brighton, Ontario, Canada