Susan Fox Hirschmann on sun 11 sep 11
already bisqued pieces?
Yep...I fire on a bed of alumina hydrate, for them to move easily during fi=
=3D
ring.
Thanks!
Susan
susan fox hirschmann
www.potteryart.biz
=3DC2=3DA0
--- On Sun, 9/11/11, William & Susan Schran User wrote:
From: William & Susan Schran User
Subject: Re: Do you need to slow down firings at quartz inversion temp for =
=3D
already bisqued pieces?
To: "Susan Fox Hirschmann"
Date: Sunday, September 11, 2011, 2:11 PM
Susan,
As with anything else there is always a but...
Large flat forms, fired in an electric kiln, elements around the perimeter,=
=3D
heat transmitted from edges to center of kiln =3DE2=3D80=3D93 yes, a slowe=
r firi=3D
ng indeed.
Placing large flat forms on bed of fine grog or the like also allows for fr=
=3D
eedom of movement while form is shrinking, and more even heat across the su=
=3D
rface.
Some forms do requires special handling & firing.
Bill
On 9/11/11 1:39 PM, "Susan Fox Hirschmann" wr=
=3D
ote:
Bill.....but with larger =3DC2=3DA0porcelain plates.....
I find slow is better.
Do you do any plate forms with that quick=3D20
a ramp to 1500??
I find slow up and slow down, prevents any possible quartz inversion
cracking on larger plates (14" and bigger.) I also go very slow with large =
=3D
porcelain tiles.
Jeff Zamek once advised me that 50 degrees an hour was best for glaze firin=
=3D
g for those to ^6....I didn't go quite that slow....but found that my firin=
=3D
gs running 20 hrs, full kiln, electric 10 cu ft....all porcelain tile forms=
=3D
(commissioned for large wall installation) prevented both cracking and war=
=3D
ping.=3D20
So I think slower firings are necessary when doing larger porcelain flat fo=
=3D
rms. At least for me.
Regards,
Susan
susan fox hirschmann
www.potteryart.biz =3D20
=3DC2=3DA0
--- On Sun, 9/11/11, William & Susan Schran User wrote:
From: William & Susan Schran User
Subject: Re: Do you need to slow down firings at quartz inversion temp for =
=3D
already bisqued pieces?
To: Clayart@LSV.CERAMICS.ORG
Date: Sunday, September 11, 2011, 10:05 AM
On 9/11/11 4:50 AM, "DJ Brewer" =3D
ail.yahoo.com/mc/compose?to=3D3Ddjbrewer88@COMCAST.NET> > wrote:
> I follow that basic guideline for both greenware and bisqueware. =3DC2=3D=
A0Is=3D
it
> an unnecessary slowdown for already bisqued pieces?
> Advice and info? =3DC2=3DA0(are my quartz inversion temps off? I'm just f=
ollo=3D
wing
> what I learned from my ceramics professor)
For greenware in bisque firing, ok.
For glazed bisque ware in a glaze firing, I just crank it up.
At school in gas kiln, we're up to 1400F in two hours.
At home in crystalline glaze firings, 1500F in two hours.
Never had any cracking issues.
Bill
--
William "Bill" Schran
wschran@cox.net co=3D
x.net>=3D20
wschran@nvcc.edu @n=3D
vcc.edu>=3D20
http://www.creativecreekartisans.com =3D
>=3D20
William & Susan Schran User on sun 11 sep 11
already bisqued pieces?
On 9/11/11 4:50 AM, "DJ Brewer" wrote:
> I follow that basic guideline for both greenware and bisqueware. Is it
> an unnecessary slowdown for already bisqued pieces?
> Advice and info? (are my quartz inversion temps off? I'm just following
> what I learned from my ceramics professor)
For greenware in bisque firing, ok.
For glazed bisque ware in a glaze firing, I just crank it up.
At school in gas kiln, we're up to 1400F in two hours.
At home in crystalline glaze firings, 1500F in two hours.
Never had any cracking issues.
Bill
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
Ron Roy on sun 11 sep 11
already bisqued pieces?
Hi DJ,
I have never slowed down at the quartz inversion on the way up in 50
years of firing - I say it doesn't matter.
I have cured quartz dunting on the way down by slowing the cooling
around the quartz inversion.
RR
Quoting DJ Brewer :
> Once a piece is bisqued, do you need to slow down the firing ramp at
> quartz inversion? I always slow down my firings from around 950 to 1250
> to between 75 to 100 degrees an hour, then pick it up to 250 to 300 an
> hour til I reach 200 degrees less than the target cone, then slow it
> down to 100 degrees an hour til it reaches cone.
>
> I follow that basic guideline for both greenware and bisqueware. Is it
> an unnecessary slowdown for already bisqued pieces?
>
> Advice and info? (are my quartz inversion temps off? I'm just following
> what I learned from my ceramics professor)
>
> DJ
>
Michael Wendt on sun 11 sep 11
already bisqued pieces?
DJ,
Since the bisque temperature normally does not
vitrify the clay, quartz inversion happens every
time the piece goes through that range.
I found that I could tell when a piece cracked
(on the way up or on the way down) by things
like location of crack or if the crack was open or
nearly invisible.
Ultimately, I discovered that large platters could
be fired safely by making sectional saggars slightly
shorter than the kiln posts (this avoids rocking
or shelf support issues) to ring the piece and slow
edge cooling.
Slowing cooling through this temperature range is a
good way to vaoid quartz inversion caused cracking
but too fast cooling can crack a piece vitually at any
temperature if the edge is heated or cooled substantially
faster than the center so slow heat and cool profiles
as a must for these types of items.
I will post a photo of the saggar parts I make on my clayart
page when I get the cahnce.
Regards,
Michael Wendt
DJ wrote:
Once a piece is bisqued, do you need to slow down the firing
ramp at
quartz inversion? I always slow down my firings from around
950 to 1250
to between 75 to 100 degrees an hour, then pick it up to 250
to 300 an
hour til I reach 200 degrees less than the target cone, then
slow it
down to 100 degrees an hour til it reaches cone.
I follow that basic guideline for both greenware and
bisqueware. Is it
an unnecessary slowdown for already bisqued pieces?
Advice and info? (are my quartz inversion temps off? I'm
just following
what I learned from my ceramics professor)
DJ
Susan Fox Hirschmann on sun 11 sep 11
already bisqued pieces?
Bill.....but with=3DA0larger =3DA0porcelain plates.....
I find slow is better.
Do you do any plate forms with that quick=3D20
a ramp to 1500??
I find slow up and slow down, prevents any possible quartz inversion
cracking on larger plates (14" and bigger.) I also go very slow with large =
=3D
porcelain tiles.
Jeff Zamek once advised me that 50 degrees an hour was best for glaze firin=
=3D
g for those to ^6....I didn't go quite that slow....but found that my firin=
=3D
gs running 20 hrs, full kiln, electric 10 cu ft....all porcelain tile forms=
=3D
(commissioned for large wall installation) prevented both cracking and war=
=3D
ping.=3D20
So I think slower firings are necessary when doing larger porcelain flat fo=
=3D
rms. At least for me.
Regards,
Susan
susan fox hirschmann
www.potteryart.biz
=3DA0
--- On Sun, 9/11/11, William & Susan Schran User wrote:
From: William & Susan Schran User
Subject: Re: Do you need to slow down firings at quartz inversion temp for =
=3D
already bisqued pieces?
To: Clayart@LSV.CERAMICS.ORG
Date: Sunday, September 11, 2011, 10:05 AM
On 9/11/11 4:50 AM, "DJ Brewer" wrote:
> I follow that basic guideline for both greenware and bisqueware.=3DA0 Is =
it
> an unnecessary slowdown for already bisqued pieces?
> Advice and info?=3DA0 (are my quartz inversion temps off? I'm just follow=
in=3D
g
> what I learned from my ceramics professor)
For greenware in bisque firing, ok.
For glazed bisque ware in a glaze firing, I just crank it up.
At school in gas kiln, we're up to 1400F in two hours.
At home in crystalline glaze firings, 1500F in two hours.
Never had any cracking issues.
Bill
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
DJ Brewer on sun 11 sep 11
already bisqued pieces?
Whoa!!!! that's FAST!!!
still, I am doing facemugs and facejugs of uneven thicknesses. I think
I'll take a slightly more cautious approach when I'm doing those.
DJ
On 9/11/2011 9:05 AM, William & Susan Schran User wrote:
> On 9/11/11 4:50 AM, "DJ Brewer" wrote:
>> I follow that basic guideline for both greenware and bisqueware. Is it
>> an unnecessary slowdown for already bisqued pieces?
>> Advice and info? (are my quartz inversion temps off? I'm just following
>> what I learned from my ceramics professor)
> For greenware in bisque firing, ok.
> For glazed bisque ware in a glaze firing, I just crank it up.
> At school in gas kiln, we're up to 1400F in two hours.
> At home in crystalline glaze firings, 1500F in two hours.
> Never had any cracking issues.
>
> Bill
>
marci Boskie's Mama =3D^..^=3D on mon 12 sep 11
already bisqued pieces?
> DJ Brewer said:
>Once a piece is bisqued, do you need to slow down the firing ramp at
>quartz inversion? I always slow down my firings from around 950 to 1250
>to between 75 to 100 degrees an hour, then pick it up to 250 to 300 an
>hour til I reach 200 degrees less than the target cone, then slow it
>down to 100 degrees an hour til it reaches cone.
All I can speak to is porcelain . I refire both my own cone 6
porcelain and commercially made cone 10 porcelain multiple times...(
sometimes as many as 7 or 8 times ) to as low as cone 018 (
approximately 1320 F / 715 C ) and as high as cone 015 (
approximately 1480 F / 800 C ) to china paint them . I ve done
this with bisque and with glazed pieces and I often fire in
my Paragon Home Artist kiln which I can fire in about 45 minutes (
and also can crash cool by opening the lid. ) so I set the kiln for
1 ramp and crack it as fast as it will go ... I do that in my large
Olympic as well but it takes about 3 hours to fire because of the
size of the kiln .
I have only ever had one piece crack and that was an 8 x 10
commercially made porcelain ( not earthenware) tile. I do try to put
stilts under larger pieces so they arent sitting directly on the kiln
shelf.. but I often do just set them on the shelf...
So.............for me , quartz inversion has not been an issue...
but again , it may be just my circumstances and it may be a real
issue with other clays..... Your mileage may vary .
marci the chinapainter
Ron Roy on tue 13 sep 11
already bisqued pieces?
Ivor makes a good point here about recognizing the kind of crack you
are looking at and why it happened.
The crack that happen on the way up in a bisque kiln looks different
than one that happens on the way down - same for cracks in a glaze
firing.
The Hamer dictionary has 10 pages on cracks - you match the picture of
the crack in the book with the crack in your pot and there is the
explanation of how it happened.
RR
Quoting ivor and olive lewis :
> Dear DJ Brewer,
> Have faith in your Ceramics Professor ? Provided your teacher was using =
the
> F scale then range you give seem to be OK.
> The important thing is, were you taught how to recognise the difference
> between a Dunt that happens when you are refiring your bisque ware to
> vitrification and a Dunt that happens when residual Quartz in the vitrifi=
ed
> body changes phase during cooling.
> Regards,
> Ivor Lewis,
> REDHILL,
> South Australia
>
ivor and olive lewis on thu 15 sep 11
already bisqued pieces?
Thanks Ron,
One of the first things I did when I found out about Hamer's Dictionary was
to photocopy that section on cracks and cracking. Invaluable information
when dealing with mature students. I would recommend all clay arts students
to do likewise if they cannot afford to buy the volume.
I was lucky to find a copy on a second hand stall at a local cultural
festival. It was half price, a bargain for a first edition. I obtained a 1s=
t
edition of Rhodes Clay and Glazes from the same source a couple of years ag=
o
for $5.50 and a couple of weeks ago our local travelling library gave me a
copy of Pioneer Pottery. My original copy is much the worse for wear,
falling apart after thirty five years of fair wear and tear.
If claywork is being abandoned in schools and institutions librarians will
start to weed unneeded books from library shelves. Some of our community
might consider making pre-emptive bids for potential "throwaways".
Best regards,
Ivory
----- Original Message -----
From:
To: "ivor and olive lewis"
Cc:
Sent: Wednesday, September 14, 2011 3:06 AM
Subject: Re: Do you need to slow down firings at quartz inversion temp for
already bisqued pieces?
> Ivor makes a good point here about recognizing the kind of crack you are
> looking at and why it happened.
>
> The crack that happen on the way up in a bisque kiln looks different tha=
n
> one that happens on the way down - same for cracks in a glaze firing.
>
> The Hamer dictionary has 10 pages on cracks - you match the picture of
> the crack in the book with the crack in your pot and there is the
> explanation of how it happened.
>
> RR
>
>
> Quoting ivor and olive lewis :
>
>> Dear DJ Brewer,
>> Have faith in your Ceramics Professor ? Provided your teacher was using
>> the
>> F scale then range you give seem to be OK.
>> The important thing is, were you taught how to recognise the difference
>> between a Dunt that happens when you are refiring your bisque ware to
>> vitrification and a Dunt that happens when residual Quartz in the
>> vitrified
>> body changes phase during cooling.
>> Regards,
>> Ivor Lewis,
>> REDHILL,
>> South Australia
>>
>
>
>
>
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