BVCuma on sun 22 dec 02
Yup..petroleum jelly...it works!
Making a quantity of plaster masters
for various number of squares grid glaze testing tiles...
I happened to try vasoline to seal
the gaps in the outer mould wood/formica/clamp frame...
It did not work so I resumed using the coil of clay
smeared into the corners with a finger tip method.
I noticed how greasy the clay became
when "contaminated" by the substance.
So I wanted to see how strange throwing
might be if I wedged it into the body...
just for fun.. as I figured it would not work at all.
Testing started at 3 grams per 1 kg plastic clay.
The body was radically altered until well wedged/blended...
which rendered it unnoticable except for improved plasticity.
The body I was working with had 1/2 percent cotton fibre,
4% 200 mesh ground hard fire brick (kyanite I'm told)
10% dust to 100's mix mesh hard fire brick grog.
Upon throwing I found a strong tendancy
to slump and compensated with thicker thrown walls.
Now this was good because the next batch
could be boosted with non plastic fines/grogs
to create a more heavy duty robust body.
Upping the cotton strand content to 1 % dry weight
(though I feel dropping back down to .75% will be optimum)
and maintaining the 4% 200 mesh kyanite brick fines,
the dust/100 mix mesh boosted upto 13%
and an additional 7% sillimanite grog straight 100's
Thereby doubling the quantity of grog and cotton fibre.
So without the benifit of aging I tested it out
and found it ungainly and difficult...
particularly when throwing large forms.
Whereupon the pulled wall loses integrity
and becomes lumpy in sections...
like continental drift, large sections shifting...distorting
(too much fibre content)
Overnight I recalled that the body was designed
as such to use the petroleum jelly addition...
I had got caught up in the before vasoline testing
for comparison and its dissapointing outcome.
Today wedging in the 3 gram/1Kg ..
I was very impressed with the near ideal results...
thin walled, tough as nails, do as you please perfomance...
trimming is just fine too....no tool clogging.
I simply did not realize how radical the impact could be!
Anyone can try this...
just wedge in a small amount of PJ..
It will feel really weird till fully blended.
(no not peanutbutter and jelly)
If your body is well balanced, 3 grams
will generate a slumping quality...use 1 gram
If you are working with a short body..
this should improve the condition...
test it out.
Bvcuma
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