[Clayart] Recycled Southern ice porcelain clay.
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Clay art
Jul 28, 2013, 8:09:59 AM7/28/13
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I wonder if one of you ever experienced an acne type appearance ( tiny
spots the size of pinheads over broad surfaces) on the final fired porcelain
works from reclaimed clay. I sanded one of them, just to discover a tiny
hole underneath.
This is on unglazed surfaces, although I suspect it may do the same on
glazed surfaces.
I soak my bisque firing to get rid of impurities.
I cannot recall that I had that problem when I first started using Southern
Ice so I contacted Les Blakebrough about it and the advice that I got from
him is not to use recycled porcelain. That is very difficult to do, since
my clay is so expensive and I recycle about half off the clay that I use on
the wheel from trimming.
I recycle and throw on plaster bats.
Thanks.
Antoinette Badenhorst
www.porcelainbyAntoinette.com
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spots the size of pinheads over broad surfaces) on the final fired porcelain
works from reclaimed clay. I sanded one of them, just to discover a tiny
hole underneath.
This is on unglazed surfaces, although I suspect it may do the same on
glazed surfaces.
I soak my bisque firing to get rid of impurities.
I cannot recall that I had that problem when I first started using Southern
Ice so I contacted Les Blakebrough about it and the advice that I got from
him is not to use recycled porcelain. That is very difficult to do, since
my clay is so expensive and I recycle about half off the clay that I use on
the wheel from trimming.
I recycle and throw on plaster bats.
Thanks.
Antoinette Badenhorst
www.porcelainbyAntoinette.com
_______________________________________________
Clayart mailing list
Cla...@ceramicist.org
Make changes to your subscription, or unsubscribe, at: http://lists.ceramicist.org/mailman/listinfo/clayart
William & Susan Schran User
Jul 28, 2013, 10:15:34 AM7/28/13
to New ClayArt Mailing List
Can't answer your question of specifically what is causing the problem,
but either a contaminant or a separation of materials in the porcelain
while at the slurry stage might be things to look at first.
Several years ago I took a group of students to a workshop with Tom
Turner. We used his porcelain and he spoke about his reclaim process. He
built a special wooden box splash pan on his wheel he used for trimming.
It was built larger than normal pans to catch all his trimmings. Any
trimmings that went on the floor he would throw out. He allowed all the
trimmings to dry until he had a larger amount. He would add the dried clay
to water, soak a bit, then use mixer on a drill to beat into a smooth
slurry. He would then dry the slurry until correct moisture content. He
said this method kept out contaminants and did not allow materials in the
porcelain to separate out as the slurry sat over time.
Hope this helps.
Bill
--
William "Bill" Schran
wsc...@cox.net
wsc...@nvcc.edu
http://www.creativecreekartisans.com
On 7/28/13 8:09 AM, "Clay art" <clayart...@gmail.com> wrote:
>I wonder if one of you ever experienced an acne type appearance ( tiny
>spots the size of pinheads over broad surfaces) on the final fired
>porcelain
>works from reclaimed clay. I sanded one of them, just to discover a tiny
>hole underneath.
but either a contaminant or a separation of materials in the porcelain
while at the slurry stage might be things to look at first.
Several years ago I took a group of students to a workshop with Tom
Turner. We used his porcelain and he spoke about his reclaim process. He
built a special wooden box splash pan on his wheel he used for trimming.
It was built larger than normal pans to catch all his trimmings. Any
trimmings that went on the floor he would throw out. He allowed all the
trimmings to dry until he had a larger amount. He would add the dried clay
to water, soak a bit, then use mixer on a drill to beat into a smooth
slurry. He would then dry the slurry until correct moisture content. He
said this method kept out contaminants and did not allow materials in the
porcelain to separate out as the slurry sat over time.
Hope this helps.
Bill
--
William "Bill" Schran
wsc...@cox.net
wsc...@nvcc.edu
http://www.creativecreekartisans.com
On 7/28/13 8:09 AM, "Clay art" <clayart...@gmail.com> wrote:
>I wonder if one of you ever experienced an acne type appearance ( tiny
>spots the size of pinheads over broad surfaces) on the final fired
>porcelain
>works from reclaimed clay. I sanded one of them, just to discover a tiny
>hole underneath.
Gayle Bair
Jul 28, 2013, 2:04:38 PM7/28/13
to New ClayArt Mailing List
Hi Antoinette,
I experienced the "acne" with Coleman clay and was told it was from the wee
dry bits of clay inside the plastic bag.
When opening the bag the dried bits on the inside of the bag would fly off
onto the moist clay. I noticed it but didn't think it would be an issue.
The "acne" didn't show up until it was fired. I didn't sand them so don't
know if there were holes under those ugly bumps on my piece.
After that I made sure to keep a damp cloth on top the the clay and/or
spray the inside of the bag to keep the bits wet. Wiping the inside of the
bag after using the clay might help or make your balls of clay and keeping
them damp wrapped might work too.
hope this helps,
Gayle
Gayle Bair Pottery
ga...@claybair.com
www.claybair.com
I experienced the "acne" with Coleman clay and was told it was from the wee
dry bits of clay inside the plastic bag.
When opening the bag the dried bits on the inside of the bag would fly off
onto the moist clay. I noticed it but didn't think it would be an issue.
The "acne" didn't show up until it was fired. I didn't sand them so don't
know if there were holes under those ugly bumps on my piece.
After that I made sure to keep a damp cloth on top the the clay and/or
spray the inside of the bag to keep the bits wet. Wiping the inside of the
bag after using the clay might help or make your balls of clay and keeping
them damp wrapped might work too.
hope this helps,
Gayle
Gayle Bair Pottery
ga...@claybair.com
www.claybair.com
Clay art
Jul 29, 2013, 2:36:50 PM7/29/13
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Hmmm, I will pay attention to this Gayle. Thanks.
Antoinette Badenhorst
www.porcelainbyAntoinette.com
Antoinette Badenhorst
www.porcelainbyAntoinette.com
Clay art
Jul 29, 2013, 2:51:23 PM7/29/13
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Bill I do wonder if it is not some kind of contamination, but for sure not
from collecting clay from the floor. My guess is it may be from plaster (
but it is too evenly spread), or something that leak out in the water and
get lost, or vinegar that I add to my clay water.
Another problem that I have, is that sometimes where I "cut and paste" new
clay, it creates a little ridge. I mentioned that to Les too and he could
not give me an answer, except for saying that SI does not handle attachments
well.
Here is a quote from his letter to me:
"Now this is not to say there are no difficulties. Attaching one piece to
another can be tricky - but not impossible. It 'settles" in a strange way
i.e. the silica settles out and is not easy to incorporate back into the
body, When you try it defies attempts to do so. In part it is to do with the
bentonite we use, but if you allow that the clay can be wedged, kneaded, etc
in the raw state, and so much easier that other porcelain clays, it is not
so much of a price to pay at the end of the day.
As a researcher one has to accept that what one strives for in the raw state
is in conflict with requirements in the fired state, and it is a fine
balancing act to get the two to work together. Also I never score or cutup
the surface as in attachments - the face of the piece to be attached is
dipped in casting slip and placed in position. The stickiness of the casting
slip is enough to keep the two surfaces bonded. A sponge wipes the excess
slip away and no marks show up after firing"
So I wonder if the answer is not in that silica/ bentonite composition. I
already changed my way that I paste the clay in where I cut it, so will see
how that will act in future. I am wondering if one of our scientists do not
have some answers.
By the way, I just came back from Touchstone after presenting a very
successful workshop. Eric bragged with your little red pot from your
workshop there. I loved it!
Best wishes
from collecting clay from the floor. My guess is it may be from plaster (
but it is too evenly spread), or something that leak out in the water and
get lost, or vinegar that I add to my clay water.
Another problem that I have, is that sometimes where I "cut and paste" new
clay, it creates a little ridge. I mentioned that to Les too and he could
not give me an answer, except for saying that SI does not handle attachments
well.
Here is a quote from his letter to me:
"Now this is not to say there are no difficulties. Attaching one piece to
another can be tricky - but not impossible. It 'settles" in a strange way
i.e. the silica settles out and is not easy to incorporate back into the
body, When you try it defies attempts to do so. In part it is to do with the
bentonite we use, but if you allow that the clay can be wedged, kneaded, etc
in the raw state, and so much easier that other porcelain clays, it is not
so much of a price to pay at the end of the day.
As a researcher one has to accept that what one strives for in the raw state
is in conflict with requirements in the fired state, and it is a fine
balancing act to get the two to work together. Also I never score or cutup
the surface as in attachments - the face of the piece to be attached is
dipped in casting slip and placed in position. The stickiness of the casting
slip is enough to keep the two surfaces bonded. A sponge wipes the excess
slip away and no marks show up after firing"
So I wonder if the answer is not in that silica/ bentonite composition. I
already changed my way that I paste the clay in where I cut it, so will see
how that will act in future. I am wondering if one of our scientists do not
have some answers.
By the way, I just came back from Touchstone after presenting a very
successful workshop. Eric bragged with your little red pot from your
workshop there. I loved it!
Best wishes
Antoinette Badenhorst
www.porcelainbyAntoinette.com
-----Original Message-----
From: clayart...@ceramicist.org [mailto:clayart...@ceramicist.org]
On Behalf Of William & Susan Schran User
Sent: Sunday, July 28, 2013 9:16 AM
To: New ClayArt Mailing List
Subject: Re: [Clayart] Recycled Southern ice porcelain clay.
www.porcelainbyAntoinette.com
-----Original Message-----
From: clayart...@ceramicist.org [mailto:clayart...@ceramicist.org]
On Behalf Of William & Susan Schran User
Sent: Sunday, July 28, 2013 9:16 AM
To: New ClayArt Mailing List
Subject: Re: [Clayart] Recycled Southern ice porcelain clay.
William & Susan Schran User
Jul 29, 2013, 5:21:53 PM7/29/13
to New ClayArt Mailing List
I had a great time at Touchstone.
Was Lee Bishop (volunteer studio asst) there with you?
She was a student of mine back in 1979!
Something you might consider: I have been using paperclay for ALL of my
attachments using B-Mix/Little Loafers type clays.
Wonder if this might be a good way for you to join SI together?
With SI the silica (and feldspar probably) give the whiteness and
translucency and the bentonite for plasticity.
Many porcelains suffer from the issue of silica separating out when
sitting in the slurry state.
That is why one must dry the trimmings, then soak in water and blend right
away. Might want to dry out porcelain hanging in a pillow slip instead of
on plaster.
It is hard to see if one picks up tiny bits of plaster when recycling
clay, but tiny bits will outgas at high fire and create little bubbles.
Bill
Was Lee Bishop (volunteer studio asst) there with you?
She was a student of mine back in 1979!
Something you might consider: I have been using paperclay for ALL of my
attachments using B-Mix/Little Loafers type clays.
Wonder if this might be a good way for you to join SI together?
With SI the silica (and feldspar probably) give the whiteness and
translucency and the bentonite for plasticity.
Many porcelains suffer from the issue of silica separating out when
sitting in the slurry state.
That is why one must dry the trimmings, then soak in water and blend right
away. Might want to dry out porcelain hanging in a pillow slip instead of
on plaster.
It is hard to see if one picks up tiny bits of plaster when recycling
clay, but tiny bits will outgas at high fire and create little bubbles.
Bill
Robert Harris
Jul 29, 2013, 6:47:16 PM7/29/13
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I've seen this too. I don't think it's little bits of plaster. My private
theory is that you get microscopic bits that haven't been thoroughly wetted.
I completely dry out my porcelain in a 3 gallon sterilite box. I then add
water until it sits an inch above the surface of the clay. I then let it
sit for 24 hours, and add more water if necessary. I then let it thoroughly
slake until most of the water has evaporated off the top (but the top isn't
drying) - say about 1 week. I then dry on plaster bats (after stirring up
well with a hand or sometimes a drill mixer) until it is very moist but not
sticky. Then I wedge it up - if it's still sticky I let it dry for a bit
longer, until it's moister than I'd throw with (but not sticky). Then I'll
stick it in a bag and set it aside for a month or so. After that I usually
dry it in the air just before I use it (often wedging it up with fresh out
of the bag porcelain).
Sounds a bit complicated, but it's not really, on the other hand it's not
an instant recycle.
I would also say that recycled porcelain needs to be properly kneaded
(spiral or bull's head), not just slap and slice wedging. (I count at least
60+ turns per piece)
Just my tuppen'worth
Robert
--
----------------------------------------------------
theory is that you get microscopic bits that haven't been thoroughly wetted.
I completely dry out my porcelain in a 3 gallon sterilite box. I then add
water until it sits an inch above the surface of the clay. I then let it
sit for 24 hours, and add more water if necessary. I then let it thoroughly
slake until most of the water has evaporated off the top (but the top isn't
drying) - say about 1 week. I then dry on plaster bats (after stirring up
well with a hand or sometimes a drill mixer) until it is very moist but not
sticky. Then I wedge it up - if it's still sticky I let it dry for a bit
longer, until it's moister than I'd throw with (but not sticky). Then I'll
stick it in a bag and set it aside for a month or so. After that I usually
dry it in the air just before I use it (often wedging it up with fresh out
of the bag porcelain).
Sounds a bit complicated, but it's not really, on the other hand it's not
an instant recycle.
I would also say that recycled porcelain needs to be properly kneaded
(spiral or bull's head), not just slap and slice wedging. (I count at least
60+ turns per piece)
Just my tuppen'worth
Robert
----------------------------------------------------
Benjamin Kant
Jul 29, 2013, 11:47:56 PM7/29/13
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Robert,
That's exactly what I do, too. Simon Leach has a video on this as well, and
as far as I can remember, he takes it one step further by letting it dry in
the sun (I think in Spain).
Ben
That's exactly what I do, too. Simon Leach has a video on this as well, and
as far as I can remember, he takes it one step further by letting it dry in
the sun (I think in Spain).
Ben
Clay art
Jul 29, 2013, 11:54:01 PM7/29/13
to New ClayArt Mailing List
Robert, this sounds much like some of what I was wondering about, somewhat
similar to what I think they call a filter pressing method, except to do it
by hand. At this stage I recycle every day, to keep the workload down, but
I wonder if you may not be right. I am going to try that. Thanks.
similar to what I think they call a filter pressing method, except to do it
by hand. At this stage I recycle every day, to keep the workload down, but
I wonder if you may not be right. I am going to try that. Thanks.
Antoinette Badenhorst
www.porcelainbyAntoinette.com
-----Original Message-----
From: clayart...@ceramicist.org [mailto:clayart...@ceramicist.org]
www.porcelainbyAntoinette.com
-----Original Message-----
From: clayart...@ceramicist.org [mailto:clayart...@ceramicist.org]
On Behalf Of Robert Harris
Clay art
Jul 30, 2013, 12:00:32 AM7/30/13
to New ClayArt Mailing List
Yes Lee was there. We had a group of 5; small, but had good quality time.
Thanks. I will consider all of what you suggest. It is heart wrecking if I
spent 18 hours on a peace and it comes out a mess, particularly just before
a big show..........
Thanks. I will consider all of what you suggest. It is heart wrecking if I
spent 18 hours on a peace and it comes out a mess, particularly just before
a big show..........
ivor and olive lewis
Jul 30, 2013, 2:22:47 AM7/30/13
to New ClayArt Mailing List
Dear Antoinette.
I have done some reading without reaching any defining conclusion about the
cause of your white Acne on Southern Ice. One difficulty is not having the
recipe or a list of ingredients of the clay body.
One dead end I considerer was that rather than using the classic 50/25/25
porcelain model Les Blakebrough worked from the classic Bone China recipe
and made modifications to that. However he does admit to employing Bentonite
and the makers of his product deny that Bone Ash is an ingredient.
Bentonites are clay minerals that are capable of changing their physical
properties through a process called "Ion exchange".
It could be that when reclaiming your turnings some have not fully dried. If
insufficient time is allowed for the clay to fully slake and it is disturbed
a phenomenon called "Water Impedance" is activated and fresh water cannot
penetrate the partially dry fragments. Perhaps you need to allow a longer
period of time for your reclaim to slake then blunge it well and follow up
with screening through a 80 or 100 mesh sieve..
I am still working on the influence of Plaster Slabs and Bats on clay and
will get back to you in a week or so. Problem is how to put the Ion
Exchange information into plain speaking
Sincere regards,
Ivor Lewis,
REDHILL,
South Australia
I have done some reading without reaching any defining conclusion about the
cause of your white Acne on Southern Ice. One difficulty is not having the
recipe or a list of ingredients of the clay body.
One dead end I considerer was that rather than using the classic 50/25/25
porcelain model Les Blakebrough worked from the classic Bone China recipe
and made modifications to that. However he does admit to employing Bentonite
and the makers of his product deny that Bone Ash is an ingredient.
Bentonites are clay minerals that are capable of changing their physical
properties through a process called "Ion exchange".
It could be that when reclaiming your turnings some have not fully dried. If
insufficient time is allowed for the clay to fully slake and it is disturbed
a phenomenon called "Water Impedance" is activated and fresh water cannot
penetrate the partially dry fragments. Perhaps you need to allow a longer
period of time for your reclaim to slake then blunge it well and follow up
with screening through a 80 or 100 mesh sieve..
I am still working on the influence of Plaster Slabs and Bats on clay and
will get back to you in a week or so. Problem is how to put the Ion
Exchange information into plain speaking
Sincere regards,
Ivor Lewis,
REDHILL,
South Australia
Clay art
Jul 30, 2013, 10:11:01 AM7/30/13
to New ClayArt Mailing List
Thank you Ivor. Good to hear from you. It sounds like I have to change my
recycling process. Please let me get your findings about plaster bats for
porcelain. Jack Dorthy said in his book that porcelain should not be dried
on plaster, but does not explain why. I could not find any reason, except
that some say the clay becomes short, which is not a problem I experienced
this far. I do not only throw on plaster, but dry my clay on plaster.
I would love to get that definition of Ion Exchange. Maybe that will help
me find the best way to do the cut and paste thing on my pots and understand
why the silica and bentonite does not work well together.
Best wishes.
recycling process. Please let me get your findings about plaster bats for
porcelain. Jack Dorthy said in his book that porcelain should not be dried
on plaster, but does not explain why. I could not find any reason, except
that some say the clay becomes short, which is not a problem I experienced
this far. I do not only throw on plaster, but dry my clay on plaster.
I would love to get that definition of Ion Exchange. Maybe that will help
me find the best way to do the cut and paste thing on my pots and understand
why the silica and bentonite does not work well together.
Best wishes.
Antoinette Badenhorst
www.porcelainbyAntoinette.com
-----Original Message-----
From: clayart...@ceramicist.org [mailto:clayart...@ceramicist.org]
On Behalf Of ivor and olive lewis
Sent: Tuesday, July 30, 2013 1:23 AM
To: New ClayArt Mailing List
www.porcelainbyAntoinette.com
-----Original Message-----
From: clayart...@ceramicist.org [mailto:clayart...@ceramicist.org]
On Behalf Of ivor and olive lewis
Sent: Tuesday, July 30, 2013 1:23 AM
To: New ClayArt Mailing List
Bryan Johnson
Jul 30, 2013, 10:21:31 AM7/30/13
to New ClayArt Mailing List
On Sun, Jul 28, 2013 at 7:09 AM, Clay art <clayart...@gmail.com> wrote:
> I wonder if one of you ever experienced an acne type appearance ( tiny
> spots the size of pinheads over broad surfaces) on the final fired
> porcelain
> works from reclaimed clay. I sanded one of them, just to discover a tiny
> hole underneath.
>
> The hole makes me think that it is the flux that has separated. I have to
> I wonder if one of you ever experienced an acne type appearance ( tiny
> spots the size of pinheads over broad surfaces) on the final fired
> porcelain
> works from reclaimed clay. I sanded one of them, just to discover a tiny
> hole underneath.
>
> deal with little lumps that don't slake. I slake dry scap, then mix well
> with a jiffy mixer, then screen, then mix a long time in soldner mixer.
I agree with Ivor's solution of blunging, although the readily available
piece of equipment would be a blender, which is also better at high shear
mixing.
Bryan Johnson.
Gayle Bair
Jul 30, 2013, 12:01:55 PM7/30/13
to New ClayArt Mailing List
Just to be clear..... I experienced what Antoinette described with a new
bag of Coleman porcelain clay. I was not using recycled clay. It occurred
the second time I opened the bag and the little dried bits of clay popped
off the interior of the bag onto the moist clay.
I noticed the dried bits but didn't think it would be an issue as it wasn't
with stoneware.
Like I said keeping the interior surface of the bag wet and a damp cloth
over the clay solved the issue for me.
bag of Coleman porcelain clay. I was not using recycled clay. It occurred
the second time I opened the bag and the little dried bits of clay popped
off the interior of the bag onto the moist clay.
I noticed the dried bits but didn't think it would be an issue as it wasn't
with stoneware.
Like I said keeping the interior surface of the bag wet and a damp cloth
over the clay solved the issue for me.
Clay art
Jul 30, 2013, 4:43:37 PM7/30/13
to New ClayArt Mailing List
Make sense Gayle. You maintained the wetness in the bag, while I seems to
semi dry my clay, and as soon as it allows me to get it back to a plastic
state, I work it again. In effect it appears to be wet, but the finer
particles of bentonite already changed character and did not allow to become
wet throughout. I say it is my own simple terms here. If you ever tried to
mix bentonite (CMC does the same thing) with water, you will know what I
mean. It needs to slake for a day or two or else it does what flour do when
you try to mix it instantly with hot water. It make dry lumps.
Thank you everyone, if this is not the problem, I'll be back with more
questions.
semi dry my clay, and as soon as it allows me to get it back to a plastic
state, I work it again. In effect it appears to be wet, but the finer
particles of bentonite already changed character and did not allow to become
wet throughout. I say it is my own simple terms here. If you ever tried to
mix bentonite (CMC does the same thing) with water, you will know what I
mean. It needs to slake for a day or two or else it does what flour do when
you try to mix it instantly with hot water. It make dry lumps.
Thank you everyone, if this is not the problem, I'll be back with more
questions.
Antoinette Badenhorst
www.porcelainbyAntoinette.com
-----Original Message-----
From: clayart...@ceramicist.org [mailto:clayart...@ceramicist.org]
On Behalf Of Gayle Bair
Sent: Tuesday, July 30, 2013 11:02 AM
To: New ClayArt Mailing List
Subject: Re: [Clayart] Recycled Southern ice porcelain clay.
www.porcelainbyAntoinette.com
-----Original Message-----
From: clayart...@ceramicist.org [mailto:clayart...@ceramicist.org]
On Behalf Of Gayle Bair
Sent: Tuesday, July 30, 2013 11:02 AM
To: New ClayArt Mailing List
Subject: Re: [Clayart] Recycled Southern ice porcelain clay.
Bryan Johnson
Jul 30, 2013, 5:55:49 PM7/30/13
to New ClayArt Mailing List
Gayle, did you notice if the bumps were hollow?
Bryan
Bryan
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