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woooo!!! fired strength surprise (let me add...) 'corrected'

updated mon 31 mar 97


Talbott on wed 5 mar 97

Tony Hansen's hypothesis: ... "In a worst case scenario here a potter
could increase his ware strength 6-fold by a simple glaze recipe
adjustment!" ...

Want proof? If these tests can be duplicated by you and others and
repeated with similar results time after time, then this hypothesis could
be validated... otherwise there are other forces at work that go beyond
glaze fit... and that is my nickels worth on that!!! ....Marshall
WOOOO!!! ... How many glazed bars broke at 250 lbs? Could there be
some variable other than glaze fit that caused perhaps only that one bar to
break? How many bars were in each test group? Seems out of line, as in
the laws of physics. Do not remember the stress and strain formulas but
the glazed surface can exert only so much force. I think there must be
some variable that you are overlooking that causes these results to vary so
much. What were the dimensions of these bars and what was the average
glaze (vitreous) thickness after firing? Something does not seem to add
up... think about it.... Is there a physicist in the house? ... Marshall

>----------------------------Original message----------------------------
>I did some fired strength testing bars today that were incredible.
>I had about 6 different sets of cone 06 glazed bars, all the glazes were
>beautiful, no crazing or shivering. The bar groups broke very consistently
>indicating reliable results.
>The glazeless bars broke at 1200 lbs.
>The strongest glazed bars were 1600 lbs.
>The weakest were 250!
>Again it appears that the single most profound effect on ware strength
>is glaze fit. And you simply cannot determine if your glazed ware is
>strong or weak by simply doing a visual inspection. In a worst case
>scenario here a potter could increase his ware strength 6-fold by a
>simple glaze recipe adjustment!
>Tony Hansen, IMC - Get INSIGHT 5 beta or The Magic of Fire II at
> or

{contact me directly for more information}
Celia & Marshall Talbott
Pottery By Celia
Route 114
P.O. Box 4116
Naples, Maine 04055-4116
(207)693-6100 voice and fax

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