Jim Tabor on mon 9 dec 02
I visited the Clayart info page for testing clays and thought I would
see if anyone had a suggestion for making clay bars. I've seen press
molds made to create a standard size but I have settled on a more simple
method which I think may be better than the clayart method. Any
suggestions to improve what I do would be appreciated.
For the claybody development activity, students are given a list of
materials we have that has a grid to enter amounts in parts or
percentage to columns for each body they want to make.
Materials are measured, dry blended and water is added until it is a
pliable ball the size of a cantaloupe. I check it before the bars are made.
At least 3 lumps are weighed to 100 grams each. They have to make at
least 3 bars for each claybody.
They are rolled into a ball and then a thick coil about 1" x 3.5"+-.
Double spread newspaper is laid out so 2 pages will be under the bars
and when rolled out and the paper is folded over so two pages will cover
the bars.
The first coil is placed near the fold on the paper with 3/8" dowels on
either side of the clay to be rolled into a uniform thickness.
The next bar is laid near the first and a dowel moved over so it can be
rolled out. Repeat for third and more bars. Bars are never moved on the
paper.
A very thin line is drawn lightly down the center and thin marks at 10cm
are added.
Identity added and the paper is folded over to allow more even drying in
the cabinet.
The paper is lifted by the sides that will not allow the bars to bend
when moved.
Dry shrinkage is recorded. Bisque shrinkage recorded and after firing to
cone 1 (our normal firing temp) the shrinkage is measured again.
Bars are weighed when they are removed from the final firing and again
after they are soaked 24+ hours (no hot plate to boil them).
Extra clay that wasn't used in the bars is made into small pots for
testing glaze fit. Our house base is used for a single dip and partial
cross dip with insides poured. Ink test and 50x reflective microscope.
Notes are entered into the computer to compare compositions.
jt
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