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bisque firing question

updated mon 9 feb 04

 

Patrick Logue on tue 11 dec 01


Hi
I would like to know how you folks judge when the
moisture is sufficiently burned away to allow a turn
up in bisque .( I know, thats a run on. its early)
I usually get it right but every now and then, BAM.
I know there are many variables too, just wondered if
there were any reliable tricks out there.
thanks
Pat

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Sarah House on tue 11 dec 01


I hold a piece glass near the top peep and watch for steam to condense on
it. If there is any fog it's not ready to turn up.
Sarah House

> I would like to know how you folks judge when the
> moisture is sufficiently burned away to allow a turn
> up in bisque





--

www.SKHPottery.com

PO Box 84
Little Switzerland, NC 28749

828-756-1191

Cindy Strnad on tue 11 dec 01


Dear Pat,

The most important thing in bisque firing is to
keep the pots at below boiling temperature
(whatever that may be at your altitude) until all
the free moisture has burned off. If I'm firing a
large sculptural piece, I may hold for as long as
12 hours. If I did thicker work, I would hold it
longer. It's a judgement call, and my methods
aren't chosen by the scientific method but purely
by intuition. (and fear) If I spent a lot of time
on the stuff in the kiln and if it has thick
joints or whatevers, I will hold longer than usual
(4 hours). If the stuff is pretty normal, I'll
hold 2 hours. If it's all thin candle cups or
plates or something, I'll only hold an hour. After
that, I fire at 150/hr up to 500 F, then at
200/hr to my final temperature, then hold an
hour.

Best wishes,

Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
USA
cindy@earthen-vessels-pottery.com
http://www.earthen-vessels-pottery.com

Ron Roy on thu 13 dec 01


There is no pat answer to this - it depends.

Moisture at the spy means there is still water in the clay and/or the kiln.
If the clay inside is all fairly thin (1/4 inch) it may still be safe to
turn up the heat even if the ware is not completely dry.

Either there is moisture or there is not although you will see less as it
dissipates. If you want to be sure - no mater how thick the clay is wait
till no moisture is coming out. If your ware is well dried it will not take
long - perhaps a couple of hours.

If humidity is high there will be lots of atmospheric H2O in the bricks
you have to realize - that will slow down evaporation from the ware - so
the whole process takes longer.

One switch on low over night with the lid just cracked is a safe way to do it.

just remember - the thicker the clay the more danger and the longer it will
take.

Ware that is not cool on your cheek (face) is dry - no evaporation going on.

RR

>I hold a piece glass near the top peep and watch for steam to condense on
>it. If there is any fog it's not ready to turn up.
>Sarah House
>
>> I would like to know how you folks judge when the
>> moisture is sufficiently burned away to allow a turn
>> up in bisque

Ron Roy
RR# 4
15084 Little Lake Rd..
Brighton,
Ontario, Canada
KOK 1H0
Residence 613-475-9544
Studio 613-475-3715
Fax 613-475-3513

Barry Howe Photography on thu 5 feb 04


Ellie,
I would guess that the pug mill that your your clay supplier is using is getting pieces of metal in the clay. If you have been using porcelain for 5 years without contamination, then it has to be the clay mixing machine.

-----Original Message-----
From: Ellie Blair
Sent: Feb 5, 2004 9:16 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: bisque firing question

GH,

I am positive. I only use porcelain clay and have been buying the same clay for 5 years. I have talked to the supplier about it but to no avail. It may be speckled but not intentionaly.
Thanks for the response.
Ellie
----- Original Message -----
From: Gary Harvey
To: CLAYART@LSV.CERAMICS.ORG
Sent: Thursday, February 05, 2004 7:06 PM
Subject: Re: bisque firing question


Are you sure you aren't buying speckled clay? That clay is designed that
way.GH
----- Original Message -----
From: "Ellie Blair"
To:
Sent: Thursday, February 05, 2004 9:38 AM
Subject: bisque firing question


Hi all,

I have a question on bisque firing. I have been having problems with the
clay I get from my local supplier. It has little tiny specks of what looks
like rust or metal. It is all through the clay and is impossible to sand
out. I do crystalline and need a nice smooth body to glaze. I have tried
everything that has been suggested to me and so far I am stil seeing bits in
my bisque. These little bits either pit or serve as a nucelous for the
crystal which is fine if you want one there but when you are dealing with a
lot it has a dramatic effect on the glazes and the results aren't a sellable
pot. I am currently bisque firing to 08 and am doing a slow fire in my
Skutt 1028. I clean my area and tools after each set down at my wheel.
This hasn't made any difference either. I would welcome any suggestions the
group may have. I am not in a position to make my own clay and have to rely
on a local supplier because it is so expensive to ship clay.

Thanks
Ellie Blair
Blair Pottery

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Ellie Blair on thu 5 feb 04


Hi all,

I have a question on bisque firing. I have been having problems with =
the clay I get from my local supplier. It has little tiny specks of =
what looks like rust or metal. It is all through the clay and is =
impossible to sand out. I do crystalline and need a nice smooth body to =
glaze. I have tried everything that has been suggested to me and so far =
I am stil seeing bits in my bisque. These little bits either pit or =
serve as a nucelous for the crystal which is fine if you want one there =
but when you are dealing with a lot it has a dramatic effect on the =
glazes and the results aren't a sellable pot. I am currently bisque =
firing to 08 and am doing a slow fire in my Skutt 1028. I clean my area =
and tools after each set down at my wheel. This hasn't made any =
difference either. I would welcome any suggestions the group may have. =
I am not in a position to make my own clay and have to rely on a local =
supplier because it is so expensive to ship clay.

Thanks
Ellie Blair
Blair Pottery

logan johnson on thu 5 feb 04


Hi Ellie,
It doesn't sound like your firing process is your issue . It sounds like your clay of choice is . If changing your clay isn't an option then try to find a compatable WHITE clay body & brush a thick enough( only found through testing) coating of the slip on top of your pieces before the firing. A little burnishing might be nice after the slip application.
Hope this helps!! LOL!!

Ellie Blair wrote:
Hi all,

I have a question on bisque firing. I have been having problems with the clay I get from my local supplier. It has little tiny specks of what looks like rust or metal. It is all through the clay and is impossible to sand out. I do crystalline and need a nice smooth body to glaze. I have tried everything that has been suggested to me and so far I am stil seeing bits in my bisque. These little bits either pit or serve as a nucelous for the crystal which is fine if you want one there but when you are dealing with a lot it has a dramatic effect on the glazes and the results aren't a sellable pot. I am currently bisque firing to 08 and am doing a slow fire in my Skutt 1028. I clean my area and tools after each set down at my wheel. This hasn't made any difference either. I would welcome any suggestions the group may have. I am not in a position to make my own clay and have to rely on a local supplier because it is so expensive to ship clay.

Thanks
Ellie Blair
Blair Pottery

______________________________________________________________________________
Send postings to clayart@lsv.ceramics.org

You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/

Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.

Logan Johnson Audeo Studios
www.audeostudios.com
"Carpe Argillam!!"

Jan L. Peterson on thu 5 feb 04


Any other local suppliers? Jan the Alleycat

Gary Harvey on thu 5 feb 04


Are you sure you aren't buying speckled clay? That clay is designed that
way.GH
----- Original Message -----
From: "Ellie Blair"
To:
Sent: Thursday, February 05, 2004 9:38 AM
Subject: bisque firing question


Hi all,

I have a question on bisque firing. I have been having problems with the
clay I get from my local supplier. It has little tiny specks of what looks
like rust or metal. It is all through the clay and is impossible to sand
out. I do crystalline and need a nice smooth body to glaze. I have tried
everything that has been suggested to me and so far I am stil seeing bits in
my bisque. These little bits either pit or serve as a nucelous for the
crystal which is fine if you want one there but when you are dealing with a
lot it has a dramatic effect on the glazes and the results aren't a sellable
pot. I am currently bisque firing to 08 and am doing a slow fire in my
Skutt 1028. I clean my area and tools after each set down at my wheel.
This hasn't made any difference either. I would welcome any suggestions the
group may have. I am not in a position to make my own clay and have to rely
on a local supplier because it is so expensive to ship clay.

Thanks
Ellie Blair
Blair Pottery

____________________________________________________________________________
__
Send postings to clayart@lsv.ceramics.org

You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/

Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.

Ellie Blair on thu 5 feb 04


GH,

I am positive. I only use porcelain clay and have been buying the same =
clay for 5 years. I have talked to the supplier about it but to no =
avail. It may be speckled but not intentionaly.
Thanks for the response.
Ellie
----- Original Message -----=20
From: Gary Harvey=20
To: CLAYART@LSV.CERAMICS.ORG=20
Sent: Thursday, February 05, 2004 7:06 PM
Subject: Re: bisque firing question


Are you sure you aren't buying speckled clay? That clay is designed =
that
way.GH
----- Original Message -----
From: "Ellie Blair"
To:
Sent: Thursday, February 05, 2004 9:38 AM
Subject: bisque firing question


Hi all,

I have a question on bisque firing. I have been having problems with =
the
clay I get from my local supplier. It has little tiny specks of what =
looks
like rust or metal. It is all through the clay and is impossible to =
sand
out. I do crystalline and need a nice smooth body to glaze. I have =
tried
everything that has been suggested to me and so far I am stil seeing =
bits in
my bisque. These little bits either pit or serve as a nucelous for =
the
crystal which is fine if you want one there but when you are dealing =
with a
lot it has a dramatic effect on the glazes and the results aren't a =
sellable
pot. I am currently bisque firing to 08 and am doing a slow fire in =
my
Skutt 1028. I clean my area and tools after each set down at my =
wheel.
This hasn't made any difference either. I would welcome any =
suggestions the
group may have. I am not in a position to make my own clay and have =
to rely
on a local supplier because it is so expensive to ship clay.

Thanks
Ellie Blair
Blair Pottery

=
_________________________________________________________________________=
___
__
Send postings to clayart@lsv.ceramics.org

You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/

Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.

=
_________________________________________________________________________=
_____
Send postings to clayart@lsv.ceramics.org

You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/

Moderator of the list is Mel Jacobson who may be reached at =
melpots@pclink.com.

Ellie Blair on thu 5 feb 04


Hi Logan,
Any idea how burnishing will effect crytalline? I know that testing is =
the best way but the process is so complex that adding burnishing would =
be so much more work per piece.

Thanks
Ellie
----- Original Message -----=20
From: logan johnson=20
To: CLAYART@LSV.CERAMICS.ORG=20
Sent: Thursday, February 05, 2004 4:23 PM
Subject: Re: bisque firing question


Hi Ellie,
It doesn't sound like your firing process is your issue . It sounds =
like your clay of choice is . If changing your clay isn't an option =
then try to find a compatable WHITE clay body & brush a thick enough( =
only found through testing) coating of the slip on top of your pieces =
before the firing. A little burnishing might be nice after the slip =
application.
Hope this helps!! LOL!!

Ellie Blair wrote:
Hi all,

I have a question on bisque firing. I have been having problems with =
the clay I get from my local supplier. It has little tiny specks of what =
looks like rust or metal. It is all through the clay and is impossible =
to sand out. I do crystalline and need a nice smooth body to glaze. I =
have tried everything that has been suggested to me and so far I am stil =
seeing bits in my bisque. These little bits either pit or serve as a =
nucelous for the crystal which is fine if you want one there but when =
you are dealing with a lot it has a dramatic effect on the glazes and =
the results aren't a sellable pot. I am currently bisque firing to 08 =
and am doing a slow fire in my Skutt 1028. I clean my area and tools =
after each set down at my wheel. This hasn't made any difference either. =
I would welcome any suggestions the group may have. I am not in a =
position to make my own clay and have to rely on a local supplier =
because it is so expensive to ship clay.

Thanks
Ellie Blair
Blair Pottery

=
_________________________________________________________________________=
_____
Send postings to clayart@lsv.ceramics.org

You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/

Moderator of the list is Mel Jacobson who may be reached at =
melpots@pclink.com.

Logan Johnson Audeo Studios
www.audeostudios.com
"Carpe Argillam!!"

=
_________________________________________________________________________=
_____
Send postings to clayart@lsv.ceramics.org

You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/

Moderator of the list is Mel Jacobson who may be reached at =
melpots@pclink.com.

Ellie Blair on thu 5 feb 04


The only other one is 110 miles to the southwest.
Ellie
----- Original Message -----=20
From: Jan L. Peterson=20
To: CLAYART@LSV.CERAMICS.ORG=20
Sent: Thursday, February 05, 2004 4:27 PM
Subject: Re: bisque firing question


Any other local suppliers? Jan the Alleycat

=
_________________________________________________________________________=
_____
Send postings to clayart@lsv.ceramics.org

You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/

Moderator of the list is Mel Jacobson who may be reached at =
melpots@pclink.com.

william schran on fri 6 feb 04


Ellie wrote:>I have been having problems with the clay I get from my
local supplier. It has little tiny specks of what looks like rust or
metal. It is all through the clay and is impossible to sand out.
I am currently bisque firing to 08 and am doing a slow fire in my
Skutt 1028.<

Could very well be some contaminant from the clay supplier. It'll
certainly be very noticeable in porcelain or white stoneware. Talk to
your supplier about the problem - could be as simple as better
clean-up between runs of clay.
If you have a large quantity of this clay, how about mixing up some
white slip to see if that will resolve the issue?
FYI - as a separate issue - may I suggest you bisque fire at a higher
temperature - cone 06 or 04. This won't resolve the spotting problem,
but may resolve other potential problems.
Bill

william schran on fri 6 feb 04


Ellie wrote:>Any idea how burnishing will effect crsytalline?<

Should be just fine. A smooth surface is certainly a plus with
crystalline glazes. Probably would not have to burnish much - just
enough to get a smooth surface - eliminating any brush marks.
Bill

Ellie Blair on fri 6 feb 04


Thanks William, =20
I normally bisque to 06 but my supplier suggested I do a slow bisque at =
08 to solve the problem. Since I still have clay I am still dealing =
with the problem. I will go back to my normal way of bisque firing. =20
Thanks
Ellie
----- Original Message -----=20
From: william schran=20
To: CLAYART@LSV.CERAMICS.ORG=20
Sent: Friday, February 06, 2004 6:42 AM
Subject: Re: bisque firing question


Ellie wrote:>I have been having problems with the clay I get from my
local supplier. It has little tiny specks of what looks like rust or
metal. It is all through the clay and is impossible to sand out.
I am currently bisque firing to 08 and am doing a slow fire in my
Skutt 1028.<

Could very well be some contaminant from the clay supplier. It'll
certainly be very noticeable in porcelain or white stoneware. Talk to
your supplier about the problem - could be as simple as better
clean-up between runs of clay.
If you have a large quantity of this clay, how about mixing up some
white slip to see if that will resolve the issue?
FYI - as a separate issue - may I suggest you bisque fire at a higher
temperature - cone 06 or 04. This won't resolve the spotting problem,
but may resolve other potential problems.
Bill

=
_________________________________________________________________________=
_____
Send postings to clayart@lsv.ceramics.org

You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/

Moderator of the list is Mel Jacobson who may be reached at =
melpots@pclink.com.

Snail Scott on sat 7 feb 04


At 09:38 AM 2/5/04 -0600, you wrote:
>...the clay I get from my local supplier...has little tiny specks of what
looks like rust or metal. It is all through the clay and is impossible to
sand out. I do crystalline and need a nice smooth body to glaze.


Is the clay you are using supposed to be smooth
and white? If so, you have some grounds for
complaint. If it's not represented to be such,
(either porcelain or near-porcelain) then you
simply need to try a different, whiter clay body.
Generally speaking, the effect you've described
it why most crystalline-glaze folks stick to good
porcelain, so if your current supplier is calling
what you're getting 'porcelain', ask if they will
order another, cleaner porcelain for you. If not,
(and since you said shipping costs are an issue,)
maybe order just a little 'good' porcelain from a
mail-order supplier and use it as a slip over your
present body. Just get a little, and order various
types until you find something you can work with.
Then order more of the best. Shipping will still
cost $$, but at least the total quantities will
be smaller.

-Snail

william schran on sat 7 feb 04


Ivor wrote: > Following on from what you say, it is possible burnishing will
eliminate points or exposed minerals which would act as sites for the
nucleating of crystals.<

I suppose it's possible, but from the process that Fara Shimbo
describes in her new ebook on crystalline glazes, of inserting a tiny
piece of mineral, to form the nucleus of a crystal, in moist clay and
making certain that it is level with the clay surface and not covered
by any clay, I would think that if the exposed mineral is not covered
by burnished clay it would still create a site for a crystal.
Having not attempted this test yet, I can only speculate.
Bill

Ivor and Olive Lewis on sun 8 feb 04


Well William,
I have not accessed that book yet but it sounds like a good technique.
Did you know that about thirty or so years ago a manufacturer of
synthetic Gemstone Rough produce some remarkable raw material for the
fashion market based on Zinc silicate.
Interesting Stuff.
Best regards
Ivor Lewis. Redhill, South Australia

Ellie Blair on sun 8 feb 04


I took a workshop with Fara last summer and we did the seeding of =
crystals buy carefully inserting a very small piece of zinc crystalite. =
It was placed into the clay as soon as the piece was dry enough to =
handle. You wanted the crystallite to be flush and not raised above the =
body. Ideally a crystal would grow from the seeded site. It worked =
very well. I found that if the crystallite was raised at all it did not =
seed a crystal but just made an unsightly spot but the ones that were =
buried a little deeper did fine. I agree doing a test of burnishing a =
piece would tell the tale.
Ellie
----- Original Message -----=20
From: william schran=20
To: CLAYART@LSV.CERAMICS.ORG=20
Sent: Saturday, February 07, 2004 4:10 PM
Subject: Re: bisque firing question


Ivor wrote: > Following on from what you say, it is possible =
burnishing will
eliminate points or exposed minerals which would act as sites for the
nucleating of crystals.<

I suppose it's possible, but from the process that Fara Shimbo
describes in her new ebook on crystalline glazes, of inserting a tiny
piece of mineral, to form the nucleus of a crystal, in moist clay and
making certain that it is level with the clay surface and not covered
by any clay, I would think that if the exposed mineral is not covered
by burnished clay it would still create a site for a crystal.
Having not attempted this test yet, I can only speculate.
Bill

=
_________________________________________________________________________=
_____
Send postings to clayart@lsv.ceramics.org

You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/

Moderator of the list is Mel Jacobson who may be reached at =
melpots@pclink.com.