Kate Johnson on fri 25 feb 05
Hello, wise and helpful folk...
I had something very strange happen with my recent firing, and wondered if
you had any theories.
As you may remember, a while back I ran out of earthenware and finished up a
bag of older buff clay that fires at cone six to 8. I made plates, mugs,
and flasks with it, and got it fired a couple of weeks ago.
It came out VERY strangely--still quite absorbent, unvitrified. We thought
the kiln had accidentally been set for earthenware temps, so this week we
refired the ware, at ^8.
It is STILL somewhat absorbent, and feels odd to the touch. Not powdery,
exactly, but very dry, if that makes sense. Not the cool, hard feel that
fired high-temp clay normally has.
I decided to go ahead and glaze some of it--doesn't seem a lot of point in
firing it yet again, and what is DOUBLY odd is that when I wet it with water
to wipe off the excess clear glaze, it turned _yellowish._.
I believe this is Flint Hills buff--that is, I know it was buff, just not
sure it was Flint Hills..I plan to contact the seller to see if anyone else
has experienced such odd results. It WAS old clay, but that shouldn't have
had that kind of results--it handled well, no problems in rolling it out or
forming it.
I have used this same clay with no problems--LITERALLY the same, from the
same box. It was about 2 years old, but as I say, handled fine...
Any ideas about what might have happened?
Regards,
Kate Johnson
Graphics/Fine Arts
http://www.cathyjohnson.info/
http://www.cafepress.com/cathy_johnson/
http://www.epsi.net/graphic/
http://www.ebsqart.com/Artists/cmd_1494_profile.htm
Kate Johnson on fri 25 feb 05
Further information, below my post, snipped...
>
> It is STILL somewhat absorbent, and feels odd to the touch. Not powdery,
> exactly, but very dry, if that makes sense. Not the cool, hard feel that
> fired high-temp clay normally has.
>
> I decided to go ahead and glaze some of it--doesn't seem a lot of point in
> firing it yet again, and what is DOUBLY odd is that when I wet it with
> water
> to wipe off the excess clear glaze, it turned _yellowish._.
So. Got the glazed ware out of the kiln today, and test drove a couple of
the mugs. They work well in the microwave, the handles stay cool (hooray),
but...the bottoms turn yellowish again, and the entire mug appears to be
HEAT SENSITIVE. I made tea in one of them, and at the level of the hot tea,
the mug turned a darker color, with ligher above. This is seriously
strange...I have NEVER had anything like this happen before, and I've been
potting for 4 years or so...
They're very pretty...a nice buff color, tavern mug styles, with cobalt blue
trim, but..._heat_ sensitive?!? I'm making "mood ring" mugs now???
I would LOVE to know if anyone else has experienced anything like this...
Regards,
Kate Johnson
Graphics/Fine Arts
http://www.cathyjohnson.info/
http://www.cafepress.com/cathy_johnson/
http://www.epsi.net/graphic/
http://www.ebsqart.com/Artists/cmd_1494_profile.htm
Cindy in SD on sat 26 feb 05
Dear Kate,
I'm not sure about the color change, but I wonder if you may have
over-fired your clay? I did this once, and everything was kind of
spongy, lava-like. The thing that happened to me . . . I let a friend
into my studio and I found out later that she had put low-fire clay into
the pugmill. Oops! It looked and threw just like my ^6 stuff, but it
sure didn't fire the same.
Best wishes,
Cindy in SD
>>
>> It is STILL somewhat absorbent, and feels odd to the touch. Not
>> powdery,
>> exactly, but very dry, if that makes sense. Not the cool, hard feel
>> that
>> fired high-temp clay normally has.
>>
>> I decided to go ahead and glaze some of it--doesn't seem a lot of
>> point in
>> firing it yet again, and what is DOUBLY odd is that when I wet it with
>> water
>> to wipe off the excess clear glaze, it turned _yellowish._.
>
>
> So. Got the glazed ware out of the kiln today, and test drove a
> couple of
> the mugs. They work well in the microwave, the handles stay cool
> (hooray),
> but...the bottoms turn yellowish again, and the entire mug appears to be
> HEAT SENSITIVE. I made tea in one of them, and at the level of the
> hot tea,
> the mug turned a darker color, with ligher above. This is seriously
> strange...I have NEVER had anything like this happen before, and I've
> been
> potting for 4 years or so...
>
> They're very pretty...a nice buff color, tavern mug styles, with
> cobalt blue
> trim, but..._heat_ sensitive?!? I'm making "mood ring" mugs now???
>
> I would LOVE to know if anyone else has experienced anything like this...
>
> Regards,
> Kate Johnson
> Graphics/Fine Arts
> http://www.cathyjohnson.info/
> http://www.cafepress.com/cathy_johnson/
> http://www.epsi.net/graphic/
> http://www.ebsqart.com/Artists/cmd_1494_profile.htm
>
> ______________________________________________________________________________
>
Kim Hohlmayer on sat 26 feb 05
On Fri, 25 Feb 2005 18:32:09 -0600, Kate Johnson wrote:
> Further information, below my post, snipped...
> >
> > It is STILL somewhat absorbent, and feels odd to the touch. Not powdery,
> > exactly, but very dry, if that makes sense. Not the cool, hard feel that
> > fired high-temp clay normally has.
Kate,
Don't know what the problem is but I know it isn't the age of the clay.
The older clay gets the better it gets!
Asian cultures throughout history would make up a clay body batch and bury
it sometimes for a hundred years so the next generation or so would
have the best possible body available.
The flat platelets that make up the clay line up more and more over time so the
clay becomes more easily and finely workable. Hope this helps at
least a little.
--
Kim Hohlmayer - Stilhaven Studio
Handcraftedthis Ceramic Beads, Jewelry and Buttons
Pleasant Township, OH
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