Whether you are a studio artist or an art educator, at some time
you have to face the job of recycling or mixing your clay. Mixing or
recycling clay by hand is a fairly simple process but it also can
be: physically demanding, take up a fair amount of studio space and
it requires keen attention to protecting yourself from the hazards
of airborne dusts and flying bits of clay, etc... The same personal
protection issues pertain to mixing with the assistance of mixers
and pugmills. You need appropriate ventilation, masks and eye
protection for working with powdered or dry clay materials.
D.I.Y. = The Cheap Method
The following is a minimally dusty method to recycle clay trimmings
and other clay scrap. (This does not mean that you can skimp on
safety devices, put that mask back on!) While your clay scrap is
still moist, roll it into thumb thickness coils and place it on a
tray to dry. Remove the tray from your studio area (like a garage),
or place it in an area that has very little air movement. The key is
not to create an exposure to the finest clay dusts - they are the
ones most readily moved into room air and these dusts are the most
hazardous to your lungs. When the clay is absolutely dry, carefully
place the coils into a heavy clay bag (3 mil. or thicker), and break
the clay coils into small pieces with a mallet.
Again, we’re trying to keep dust to a minimum here, so it’s best to
wear all the safety devices mentioned, provide adequate ventilation
to remove fugitive dusts. This is an operation that can also be
performed outside.
Now, fill a 5 gallon bucket half full of water. Pour the crushed
clay into the water approximately 5 pounds per 15 minutes. Layering
in this way will allow the clay chunks to saturate with water before
they are submerged under another layer of dry clay pieces. Continue
this layering until the bucket is half full of clay.
After 4 days there will be a layer of clear water on top of the
bucket. Decant as much of this water as possible from the bucket.
Now, you will need to have a plaster tray prepared on which to
spread out the clay slurry. A framed window screen with canvas laid
across it will also function as a suitable tray. Unload the wet
slurry on to your tray to a thickness of about 2 inches (5cm). If
you notice chunks of hard clay during this process, they should be
set aside and sent through the process from the start again. Also,
be cautious when unloading the slurry, sometimes sharp tools can
make into reclaimed clay and finding them with a bare hand can
really ruin your day!
Monitor the drying process over the next two days. Remove the clay
from the trays slightly damper than you normally use it. Wedging
will cause the clay to stiffen slightly. Store reclaimed clay in
heavy weight plastic bags.
Hand Mixing from Scratch
Hand mixing from scratch follows the reclaiming process fairly
closely but you start with already dry powdered constituent
materials. The trick is getting the dry powder materials blended
without raising a lot of dust. I have seen dry clay blended outside
in a kiln yard using hoes, rakes and other farm implements. This is
messy and of course a respiratory hazard. (Anyone recognize a theme
here?) Dry materials can be sealed in a large bag and massaged about
in an effort to blend the materials, but you will be limited by how
much clay you’re physically capable of wrestling with! If you have a
ball mill, the dry materials can be loaded into a large container,
sealed and placed on the mill to turn...
By now you’ve decided to get some mixing equipment.
Rule number 1: Do not buy a pugmill when you need a mixer! Most pugmills
do not mix clay effectively, they perform other very beneficial
operations; most notably they compress and they can de-air the clay.
The augers in a pugmill perform very little in the way of a mixing
action. Augers move the clay forward through a shredder, some models
then provide a de-airing vacuum chamber and finally through a nozzle
opening.
Mixers, on the other hand continuously work the clay, distributing
water throughout the mixture until the clay is one homogenous, moist
consistency. Clay that is completely mixed is then either wedged or
then sent through a pugmill.
Selecting Mixing Equipment
There are a number of manufacturers of studio quality equipment.
Among the more popular brands are Bluebird, Soldner, Shimpo and Peter Pugger. Each has excellent safety features and this should be
number 1 in your evaluation criteria. Check the specifications:
mixers are often rated by the total batch weight the machine can
handle, and pugmills are measured in the amount of clay they can
process in an hour. Evaluate your studio’s clay use: a smaller
capacity mixer or pugmill will cost somewhat less than larger
machines, but will require a greater investment of time and energy.
A de-airing pugmill is more likely to allow the user to use the clay
without wedging right away, but most non-deairing pugmills will
provide a dense extrusion that requires only minimal wedging.
No matter which method you use, keep in mind that clay is a
wonderful material because it never needs to go to waste.
Click here to see our Clay Mixer Selection
Click here to see our Pugmill Selection |