kathleen gordon on mon 8 oct 07
Hello clayarters.. anyone else been using frost the ^6 porcelain from
laguna? I have been using it lately to make plates and bowls ...
plates are all great .. they are made on plaster molds with
slabs.Bowls are thrown and trimmed 1 or 2 days later after being left
in the drying cabinet on their plastic bats.I am finding alot of
cracking in the bottom of my bowls... some before and some after
trimming ..these cracks do not go all the way through to the inside of
the bowls... is it possible they can make it through the glaze
firing? what is causing this? i have used bmix for a long time and
have never had this trouble before ...someone suggested that perhaps i
was trimming too dry? but several of them were cracked before i even
started to trim them.. since i was new to the clay i trimmed anyway
just to see what would happen. anyone have any thoughts..I would
appreciate suggestions
--
kathleen gordon
'if things seem under control you are not going
fast enough" mario andretti
John Rodgers on tue 9 oct 07
Kathleen,
My experience has been that if a crack occurs in the bottom of a bowl
when drying, then put it back in reclaim. I have never been really
sucessful with patching cracks in bowl bottoms. Usually what happens,
even when an attempt is made to trim out the crack, when it is fired, it
will still open up, and then because the bowl is bisque, the clay is
wasted. No, don't waste your time on a cracked bowl. For the time spent
messing with it, you can throw another bowl.
Crack control - first of all, I use plaster bats, not plastic bats. Why?
As a bowl drys, that portion of the bowl sticking up in the air drys
much faster that than portion down next to the plastic bat. This
differential sets up a lot of stress in the clay - top to bottom,
contributing to the tendency to crack. To dry, the moisture must migrate
or wick up the walls of the bowl from the bottom in order to dry well.
The more evenly the moisture can be removed, the less likely there will
be cracking. I use the palster bats because the plsster bats draw the
moisture from the bottom of the bowl as the upper portion of the bowl
drys in the air. This helps even out the moisture levels and equilizes
the stresses on the clay. In time, enough moisture will be drawn by the
plaster bats to get the bowl to self release. After throwing a bowl, I
allow the bowl to air dry until the plaster releases the bowl. Then I
turn the bowl over to dry upside down on a bat until I am ready to trim
it. If the rim of the bowl is drying to fast, I will put a plastic bag
over the bowl and allw it to sit over night. This helps keep the
moisture pretty uniform though the clay. The plaster will continue
pulling moisture until it releases the bowl. Then I will uncover the
bowl and allow air crying to continue.
One thing, be sure the bottom of the bowl is well compressed. Throw with
a minimum of water - preferably with a clay slurry of the same clay as
you are throwing with. To much water tends to encourage cracking.
This is my way, based on long experience.
BTW, some potters don't like plaster bats. Claim they have problems with
plaster chips getting in the clay. I've never had that problem. I trim
my plaster bats so they do not chip.
Good luck,
Regards,
John Rodgers
Chelsea, AL
kathleen gordon wrote:
> Hello clayarters.. anyone else been using frost the ^6 porcelain from
> laguna? I have been using it lately to make plates and bowls ...
> plates are all great .. they are made on plaster molds with
> slabs.Bowls are thrown and trimmed 1 or 2 days later after being left
> in the drying cabinet on their plastic bats.I am finding alot of
> cracking in the bottom of my bowls... some before and some after
> trimming ..these cracks do not go all the way through to the inside of
> the bowls... is it possible they can make it through the glaze
> firing? what is causing this? i have used bmix for a long time and
> have never had this trouble before ...someone suggested that perhaps i
> was trimming too dry? but several of them were cracked before i even
> started to trim them.. since i was new to the clay i trimmed anyway
> just to see what would happen. anyone have any thoughts..I would
> appreciate suggestions
> --
> kathleen gordon
>
> 'if things seem under control you are not going
> fast enough" mario andretti
>
> ______________________________________________________________________________
> Clayart members may send postings to: clayart@lsv.ceramics.org
>
> You may look at the archives for the list, post messages, or change your
> subscription settings here: http://www.acers.org/cic/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at melpots2@visi.com
>
>
>
Charles Hightower on tue 9 oct 07
Kathleen,
I just ordered some frost with my next clay shipment. I have been throwing
Bmix for years. How does it throw against Bmix? Tall stuff? I make a lot of
large bulbous pots with lids. Bmix was firing too dirty in reduction.
Lynn Goodman Porcelain Pottery on tue 9 oct 07
On Oct 9, 2007, at 12:55 AM, kathleen gordon wrote:
> Hello clayarters.. anyone else been using frost the ^6 porcelain from
> laguna? I have been using it lately to make plates and bowls ...
> plates are all great .. they are made on plaster molds with
> slabs.Bowls are thrown and trimmed 1 or 2 days later after being left
> in the drying cabinet on their plastic bats.I am finding alot of
> cracking in the bottom of my bowls... some before and some after
> trimming ..these cracks do not go all the way through to the inside of
> the bowls... is it possible they can make it through the glaze
> firing? what is causing this? i have used bmix for a long time and
> have never had this trouble before ...someone suggested that perhaps i
> was trimming too dry? but several of them were cracked before i even
> started to trim them.. since i was new to the clay i trimmed anyway
> just to see what would happen. anyone have any thoughts..I would
> appreciate suggestions
> --
> kathleen gordon
Hi Kathleen,
I tried Frost and can't stand it. I also got cracking with it, plus a
hefty dose of warpage. Not to mention that I couldn't make large
things to save my life (I often throw very large). Yes, it's white
and lovely--but it aggravates me! You could try more compression on
the bottom and throwing everything on plaster bats; that's the only
thing that helped for me.
I use Standard #551 ^6 porcelain. Very white, plastic, well-behaved,
and easy to throw. Also translucent where thin. Every time I try
something else I end up cursing at it then going back to #551.
Lynn
Lynn Goodman
Fine Porcelain Pottery
Cell 347-526-9805
www.lynngoodmanporcelain.com
Forrest on tue 9 oct 07
Are you wiring the bowls and turning them upside down as soon as you can?
This helps reduce nasty bottom cracks.
Rosemary Forrest
On 10/9/07 12:55 AM, "kathleen gordon" wrote:
> Hello clayarters.. anyone else been using frost the ^6 porcelain from
> laguna? I have been using it lately to make plates and bowls ...
> plates are all great .. they are made on plaster molds with
> slabs.Bowls are thrown and trimmed 1 or 2 days later after being left
> in the drying cabinet on their plastic bats.I am finding alot of
> cracking in the bottom of my bowls... some before and some after
> trimming ..these cracks do not go all the way through to the inside of
> the bowls... is it possible they can make it through the glaze
> firing? what is causing this? i have used bmix for a long time and
> have never had this trouble before ...someone suggested that perhaps i
> was trimming too dry? but several of them were cracked before i even
> started to trim them.. since i was new to the clay i trimmed anyway
> just to see what would happen. anyone have any thoughts..I would
> appreciate suggestions
> --
> kathleen gordon
>
> 'if things seem under control you are not going
> fast enough" mario andretti
>
> ______________________________________________________________________________
> Clayart members may send postings to: clayart@lsv.ceramics.org
>
> You may look at the archives for the list, post messages, or change your
> subscription settings here: http://www.acers.org/cic/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at melpots2@visi.com
Maggie Jones on tue 9 oct 07
I would get them off the plastic batts sooner to help with keeping the
moisture content even.
Maggie
On Mon, 8 Oct 2007 21:55:12 -0700 kathleen gordon
writes:
> Hello clayarters.. anyone else been using frost the ^6 porcelain
> from
> laguna? I have been using it lately to make plates and bowls ...
> plates are all great .. they are made on plaster molds with
> slabs.Bowls are thrown and trimmed 1 or 2 days later after being
> left
> in the drying cabinet on their plastic bats.I am finding alot of
> cracking in the bottom of my bowls... some before and some after
> trimming ..these cracks do not go all the way through to the inside
> of
> the bowls... is it possible they can make it through the glaze
> firing? what is causing this? i have used bmix for a long time and
> have never had this trouble before ...someone suggested that perhaps
> i
> was trimming too dry? but several of them were cracked before i
> even
> started to trim them.. since i was new to the clay i trimmed anyway
> just to see what would happen. anyone have any thoughts..I would
> appreciate suggestions
> --
> kathleen gordon
>
> 'if things seem under control you are not going
> fast enough" mario andretti
>
>
_________________________________________________________________________
_____
> Clayart members may send postings to: clayart@lsv.ceramics.org
>
> You may look at the archives for the list, post messages, or change
> your
> subscription settings here: http://www.acers.org/cic/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots2@visi.com
>
>
Michael Wendt on wed 10 oct 07
Kathleen,
Add to your list:
wire wedge the clay 10 or 20
times. Then do a set of drying
trials.
Contrary to popular advice,
super plastic clays can be fast dried
if they are monitored and the drying
is kept uniform. See the process at:
http://www.wendtpottery.com/clayart.htm
We try to keep our Helmer "Porcelain *"
out of the damp box. As soon as the rim
is slightly firm and no longer sticky, the
pots are inverted onto smooth, clean batts.
The bottom is immediately ribbed to a gloss
with a stainless steel rib and the pots are
almost always "safe". That is, you can dry
them at the pace that fits your schedule.
For us, the fan drying continues if the timing
to trimming works, otherwise, we may stall
drying till the next day to better match our
work schedule. Once trimmed, all trim areas
are burnished with the various burnishing
tools to make them smooth and the pots
are dried in the room.
I always recommend drying trials to try to
find the best way to dry pots. Oddly, slower
is not always better with every clay.
Regards,
Michael Wendt
Wendt Pottery
2729 Clearwater Ave.
Lewiston, Id 83501
U.S.A.
208-746-3724
wendtpot@lewiston.com
http://www.wendtpottery.com
http://UniquePorcelainDesigns.com
Bowls are thrown and trimmed 1 or 2 days later after
being left
in the drying cabinet on their plastic bats.I am
finding alot of
cracking in the bottom of my bowls... some before and
some after
trimming ..these cracks do not go all the way through
to the inside of
the bowls... is it possible they can make it through
the glaze
firing? what is causing this? i have used bmix for a
long time and
have never had this trouble before ...someone suggested
that perhaps i
was trimming too dry? but several of them were cracked
before i even
started to trim them.. since i was new to the clay i
trimmed anyway
just to see what would happen. anyone have any
thoughts..I would
appreciate suggestions
--
kathleen gordon
ellen bates on thu 11 oct 07
Kathleen, I have experienced the same sort of cracking after trimming Laguna
Frost, and find that if I trim as soon as the clay can stand up to it, then
dry slowly (especially if handles, finials, etc. are attached) the cracks
can be eliminated. I dry a couple days under loose plastic, and a couple
days under newspaper to keep attachments from cracking. Cracks not
associated with attachments, I think of as "stress" cracks. Perhaps I
should consider a new set of Dolan trimming tools too.
Best, Ellen Bates
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