Ty Brunson on sat 15 jun 02
Just finished a group of terrasig horsehair pots only to discover weeks
later that the pots are suffering from pop outs. Have used 35 mesh
hawthorne bond successfully before but I suspect that it is the culprit.
Clay formula is as follows;
50lbs Hawthorne Bond 35 Mesh
50lbs Goldart
10lbs om4
10lbs 35 mesh flint (grog flint)
10lbs Custer Feldspar
Terra sig is based on Om4
Any suggestions short of changing the entire clay body ? I need a
multipurpose body that will go to cone 10 and serve as lowfire body as
well. Will going to 50 mesh HB eliminate the pop outs in an 06 soft
firing. I have isolated all of the ingredients and I am in the process of
testing them individually. Has anyone else had the same problem?
I have also noticed a degradation of the value of the carbon trailing
that happens slowly after the horsehair firing is completed. Seems to
me the black carbon trail especially the faint wispy blushing that
happens as a result of the terrasig surface starts to dissappear after
several weeks of exposure to sunlight. Eventually only the stong line
directly under the spot where the hair was placed is left. Also a color
shift from black to sepia starts to take place. Could it be residual
sulfur from the Goldart that is causing the fading and sepia shift. Is
that what causes the pots to yellow if washed off and dried while still
in the bisque state? I am testing a variety of finishes for the surface
ranging from Thompson's water seal UV protection (I know it sounds
crazy) to silicon based grout sealers and the more traditional paste
wax solution. Any advice appreciated. Thanks
Ron Roy on thu 20 jun 02
Hi Ty,
this is going to be somewhat redundant as I just posted on this subject -
but - I think you are doing exactly the right thing - test all the
materials till you find the lime - and it could be coming in the Hawthorn,
the GoldArt or the grog. When you find it simply sieve the material through
30 mesh.
By the way - vinegar or hydrofluoric acid will make lime efferves.
Lime will show up in bisque pots if they are on the shelf long enough to
absorb H2O from the air - and certainly when glaze is applied - it take a
little time and sometimes it happens during the initial stages of a glaze
firing. It can even happen after a glaze firing if the clay is not
vitrified enough.
I agree the 50 mesh Hawthorn is probably a good idea - but test it anyway -
even if you have sieved it - because your pots are nowhere near
vitrification you may still find you have a problem.
RR
>Just finished a group of terrasig horsehair pots only to discover weeks
>later that the pots are suffering from pop outs. Have used 35 mesh
>hawthorne bond successfully before but I suspect that it is the culprit.
>
>Clay formula is as follows;
>
>50lbs Hawthorne Bond 35 Mesh
>50lbs Goldart
>10lbs om4
>10lbs 35 mesh flint (grog flint)
>10lbs Custer Feldspar
>
>Terra sig is based on Om4
>
>Any suggestions short of changing the entire clay body ? I need a
>multipurpose body that will go to cone 10 and serve as lowfire body as
>well. Will going to 50 mesh HB eliminate the pop outs in an 06 soft
>firing. I have isolated all of the ingredients and I am in the process of
>testing them individually. Has anyone else had the same problem?
>
> I have also noticed a degradation of the value of the carbon trailing
>that happens slowly after the horsehair firing is completed. Seems to
>me the black carbon trail especially the faint wispy blushing that
>happens as a result of the terrasig surface starts to dissappear after
>several weeks of exposure to sunlight. Eventually only the stong line
>directly under the spot where the hair was placed is left. Also a color
>shift from black to sepia starts to take place. Could it be residual
>sulfur from the Goldart that is causing the fading and sepia shift. Is
>that what causes the pots to yellow if washed off and dried while still
>in the bisque state? I am testing a variety of finishes for the surface
>ranging from Thompson's water seal UV protection (I know it sounds
>crazy) to silicon based grout sealers and the more traditional paste
>wax solution. Any advice appreciated. Thanks
>
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Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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