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RE: Polymer Clay

Thomas Connors asked for opinions on using Plastalina Modelling Clay in his
substrate. this stuff sounds pretty much like Play Dough. I guess he wants
to form "Artistic Dupla Style Fertilizer Balls"?

Some days when I think I've just about heard everything, along comes a new

I just finished doing a bit of Web surfing. On "Polymer Clay Central", in
their Safety section (http://www0.delphi.com/polymerclay/safety.html), I
came across the following little snippet:

"Polymer clay is a part of the vast family of plastics known as PVC
(polyvinyl chlorides), and is a relative newcomer to the art world. Invented
in Germany and refined in it's multi-use capabilities in the 1930's, PVC is
a product that can take many shapes and forms. It can be hard and rigid, or
soft and malleable, and pretty much any degree in between."

"PVC is created in a 5 step process, and when using Polymer clay, the artist
is performing the last two! These steps are synthesis, polymerization,
compounding, forming, and fusing. The first two steps create the PVC in the
form of granules of varying sizes (depending on the processing). When
creating for polymer clay, the PVC is a fine powder. The third step,
compounding, is where colors, stabilizers, and plasticizers are added. It's
the plasticizers that give the PVC it's softness and malleability, the
"clay" feel, and they aid in the heating and fusing at low temperatures. The
last two steps, forming and fusing, are accomplished by the artist when he
works the clay and makes the item, and then when he bakes it to turn it into
a hard permanent plastic."

"For our use, there are two areas of concern. The plasticizers added to the
clay are classified as hazardous chemicals by OSHA. If you leave a piece of
unbaked clay on a sheet of paper for awhile, you'll notice an oily ring left
on the paper. This is the plasticizer leaching out of the clay. Because of
this, you should never work clay in the vicinity of food, and any utensils
used on the clay should never be returned to the kitchen. You might also ask
"what about my hands?". The average user would have no need for concern as
long as the hands are thoroughly washed after working the clay. Those
artists who work with the clay on a daily basis often make the concession of
wearing surgical gloves during the softening, mixing, and kneading
processes, and remove them for the detail work. Thus, exposure to the
plasticizers is minimized."

"The second area of caution is when baking the clay. In the baking process,
the individual grains of PVC held in suspension in the plasticizer begin to
swell into a gel and they fuse with other grains until the whole piece is
turned into hard, fused plastic. After baking, the plasticizers are inert
and the clay is considered non-toxic. We've found that using a temperature
about 225-240 degrees for an hour thoroughly hardens the clay and does not
cause burning. Burning the clay during the baking procedure produces very
noxious fumes that are unhealthy to breathe, so remember to have adequate
ventilation in your baking area. Ovens can be used, and some artists have
toaster ovens dedicated to the clay. And while baking makes the clay
basically inert plastic, it should never be used for anything that would
contact food, because some residual plasticizers could be released by the
acidity of certain foods."

Sorry for the extensive quote, but I think this is one idea which has to be
quashed before anyone causes unintentioned damage to the health of their
aquariums. Now, I don't know about you, but I don't think I'd use anything
in my aquariums which carried those sorts of warnings. What is the
"plasticizer" going to do to your underwater ecology? Think about it, long
and hard.

The idea of mixing clay with some fertilizer and micronized iron and forming
balls out of it is an excellent one, actually rather "tried and true" as
many people, me included, have been doing it for a while with very good
results. But please, use "real" clay, not an artifical byproduct of the
petrochemical industry.

James Purchase