William & Susan Schran User on thu 13 nov 08
On 11/12/08 4:33 PM, "Ron Roy" wrote:
> The first obvious sign that you are over firing a clay is called blebbing -
> small blisters all over the ware.
Ron,
Have not heard this expression previously.
How is this related or different than bloating?
Is this caused by materials out-gassing when clay is protoplastic?
I would think in this instance the problem is caused, not specifically form
taking the clay to ^10, but the work heat resulting from extended
temperature holds at around 2000F.
Bill
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
Ellie Blair on thu 13 nov 08
Could this be the same thing as I call pimples under the glaze? The ware w=
as over fired and all of my crystalline glaze filled the catchers.
Ellie Blair
Blair Pottery
Lawrence=2C Kansas 66047
> Date: Thu=2C 13 Nov 2008 08:23:34 -0500
> From: wschran@COX.NET
> Subject: Re: over firing/blebbing
> To: CLAYART@LSV.CERAMICS.ORG
>=20
> On 11/12/08 4:33 PM=2C "Ron Roy" wrote:
>=20
> > The first obvious sign that you are over firing a clay is called blebbi=
ng -
> > small blisters all over the ware.
> Ron=2C
> Have not heard this expression previously.
> How is this related or different than bloating?
> Is this caused by materials out-gassing when clay is protoplastic?
>=20
> I would think in this instance the problem is caused=2C not specifically =
form
> taking the clay to ^10=2C but the work heat resulting from extended
> temperature holds at around 2000F.
>=20
> Bill
>=20
> --
> William "Bill" Schran
> wschran@cox.net
> wschran@nvcc.edu
> http://www.creativecreekartisans.com
Taylor Hendrix on thu 13 nov 08
Bill:
I have not heard this in pottery before either but judging by the
word's other uses, I would say that blebbing is caused by air pockets
which remain in the clay after the forming of the piece. Not sure how
this relates to a sign of overfiring.
A quick google check dug up an About.com page with the pottery usage.
I have no idea from where the source of this particular definition
comes. so grain of salt and all.
As my professor Dr. Eselschlager used to say, "If you have a blebben
problem, mit ein pin tool in stecken!" Some days he was more grumpy
than normal.
Taylor, in Rockport TX
wirerabbit1 on Skype (-0500 UTC)
http://wirerabbit.blogspot.com
http://wirerabbitpots.blogspot.com
http://www.flickr.com/photos/wirerabbit/
On Thu, Nov 13, 2008 at 7:23 AM, William & Susan Schran User
wrote:
> On 11/12/08 4:33 PM, "Ron Roy" wrote:
>
>> The first obvious sign that you are over firing a clay is called blebbing -
>> small blisters all over the ware.
> Ron,
> Have not heard this expression previously.
> How is this related or different than bloating?
> Is this caused by materials out-gassing when clay is protoplastic?
>
> I would think in this instance the problem is caused, not specifically form
> taking the clay to ^10, but the work heat resulting from extended
> temperature holds at around 2000F.
>
> Bill
>
> --
> William "Bill" Schran
> wschran@cox.net
> wschran@nvcc.edu
> http://www.creativecreekartisans.com
>
Snail Scott on thu 13 nov 08
...called blebbing -
>> Have not heard this expression previously.
>> How is this related or different than bloating?
>> Is this caused by materials out-gassing when clay is protoplastic?
Yep. think of blebbing as baby bloating.
Neither one can happen unless the clay is vitrified
enough to seal the surface and prevent the escape of
gasses, and pyroplastic enough to distort from the
pressure.
-Snail
Suchman ceramics on fri 14 nov 08
I think I get this at ^6 reduction with b-mix and iron rich stone ware as
well.
On Thu, Nov 13, 2008 at 3:10 PM, Snail Scott wrote:
> ...called blebbing -
>
>> Have not heard this expression previously.
>>> How is this related or different than bloating?
>>> Is this caused by materials out-gassing when clay is protoplastic?
>>>
>>
>
> Yep. think of blebbing as baby bloating.
>
> Neither one can happen unless the clay is vitrified
> enough to seal the surface and prevent the escape of
> gasses, and pyroplastic enough to distort from the
> pressure.
>
> -Snail
>
--
-e-in-o'side-
pagan by nature
Ron Roy on tue 18 nov 08
Hi Bill,
I have just taken a look in my library for the term - a lot more obscure
than I thought - found one mention in Clay and Glazes for the Potter -
Rhodes.
I think it is bloating but in it's first manifestation - the clay has to be
completely vitrified so that - when the clay starts to break down and
produce gas - it first looks like small blisters. If that point is passed
then the blisters become larger.
If the blisters are over the whole pot then it's a sure sign the clay is
the problem - unless it was over fired. This is different from the kind of
bloating you get from black coring - where the blisters tend to form in
certain parts of the ware - like the thicker parts.
Could you cause a clay that was OK for cone 10 to be overfired by holding
it at 2000F for an extended period? It would depend on how long and how
close the clay was to vitrification at cone 10 - do you have any
information on how long that would take? I'm quite sure it would effect the
final vitrification - just not sure about how long it would take.
RR
>On 11/12/08 4:33 PM, "Ron Roy" wrote:
>
>> The first obvious sign that you are over firing a clay is called blebbing -
>> small blisters all over the ware.
>Ron,
>Have not heard this expression previously.
>How is this related or different than bloating?
>Is this caused by materials out-gassing when clay is protoplastic?
>
>I would think in this instance the problem is caused, not specifically form
>taking the clay to ^10, but the work heat resulting from extended
>temperature holds at around 2000F.
>
>Bill
>
>--
>William "Bill" Schran
>wschran@cox.net
>wschran@nvcc.edu
>http://www.creativecreekartisans.com
Ron Roy
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
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