Victoria E. Hamilton on sat 14 jan 06
Judy -
Lotion could well be the problem. Also, even when pots come straight from
the bisque to the glaze table, they are covered in ceramic dust. I usually
"dust" my bisque ware with a damp sponge - a little more vigorously if
they've been sitting for a while.
My mantra for all my beginning glaze workshops is "clean hands, clean work
surface, clean pots, clean tools."
I hope you find "the answer" soon.
Vicki Hamilton
Millennia Antica Pottery
Seattle, WA
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Judy Rohrbaugh
Sent: Saturday, January 14, 2006 11:33
To: CLAYART@LSV.CERAMICS.ORG
Subject: another question on glazes crawling
I have been recently working with dipping /layering glazes. I have learned
to not fire until everything is very dry, and for the past few months all
has been going well.
Now, in the past two glaze loads, I have 3-6 pots each time coming out
with crawling near the rim, usually about 1/2 from the top.
There is usually a total of three glazes here, both inside and out, all on
very thin. I have managed to glaze like this for several loads just fine,
now it's just started to happen, and I don't know why.
I am positive things are dry enough. Too thick? Doesn't seem any thicker
than before?
Dirt?
Next load, I plan to wash my pots to the "extreme." Any suggesstion as to
how? Use laundry detergent? Some of the bisque comes straight from the
kiln, and some has been sitting here, but that doesn't seem to influence
which pots get hit.
I have also wondered if I am contaminating the pots when I handle them-
hand lotion in the dead of winter?
Also, as a precaution, I thought of reheating any bisque that has been
here for awhile-maybe to get off any oils from my hands- how hot?
I don't think it's the glaze, I think it's the pots.
Has this ever happened to anyone else? I never had crawling, ever, until
recently.
Any suggestions, I appreciate.
Thanks,
Judy Rohrbaugh
Fine Art Stoneware
Ohio
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Judy Rohrbaugh on sat 14 jan 06
I have been recently working with dipping /layering glazes. I have learned to not fire until everything is very dry, and for the past few months all has been going well.
Now, in the past two glaze loads, I have 3-6 pots each time coming out with crawling near the rim, usually about 1/2 from the top.
There is usually a total of three glazes here, both inside and out, all on very thin. I have managed to glaze like this for several loads just fine, now it's just started to happen, and I don't know why.
I am positive things are dry enough. Too thick? Doesn't seem any thicker than before?
Dirt?
Next load, I plan to wash my pots to the "extreme." Any suggesstion as to how? Use laundry detergent? Some of the bisque comes straight from the kiln, and some has been sitting here, but that doesn't seem to influence which pots get hit.
I have also wondered if I am contaminating the pots when I handle them- hand lotion in the dead of winter?
Also, as a precaution, I thought of reheating any bisque that has been here for awhile-maybe to get off any oils from my hands- how hot?
I don't think it's the glaze, I think it's the pots.
Has this ever happened to anyone else? I never had crawling, ever, until recently.
Any suggestions, I appreciate.
Thanks,
Judy Rohrbaugh
Fine Art Stoneware
Ohio
Mildred Herot on sat 14 jan 06
Hi Judy: I also have had a lot of problems with crawling but discovered I
can eliminate this by glazing the interiors and wait a day or so before
glazing the exteriors,
-.....Mildred Herot---- Original Message -----
From: "Judy Rohrbaugh"
To:
Sent: Saturday, January 14, 2006 2:33 PM
Subject: another question on glazes crawling
>I have been recently working with dipping /layering glazes. I have learned
>to not fire until everything is very dry, and for the past few months all
>has been going well.
> Now, in the past two glaze loads, I have 3-6 pots each time coming out
> with crawling near the rim, usually about 1/2 from the top.
> There is usually a total of three glazes here, both inside and out, all
> on very thin. I have managed to glaze like this for several loads just
> fine, now it's just started to happen, and I don't know why.
>
> I am positive things are dry enough. Too thick? Doesn't seem any thicker
> than before?
> Dirt?
> Next load, I plan to wash my pots to the "extreme." Any suggesstion as
> to how? Use laundry detergent? Some of the bisque comes straight from the
> kiln, and some has been sitting here, but that doesn't seem to influence
> which pots get hit.
> I have also wondered if I am contaminating the pots when I handle them-
> hand lotion in the dead of winter?
> Also, as a precaution, I thought of reheating any bisque that has been
> here for awhile-maybe to get off any oils from my hands- how hot?
> I don't think it's the glaze, I think it's the pots.
>
> Has this ever happened to anyone else? I never had crawling, ever, until
> recently.
> Any suggestions, I appreciate.
> Thanks,
> Judy Rohrbaugh
> Fine Art Stoneware
> Ohio
>
> ______________________________________________________________________________
> 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.
>
Lori Doty on sat 14 jan 06
Judy,
The biggest culprit I can think of is the hand lotion. It will work
similar to wax resist and not allow the glaze to absorb into the piece
as it should. I had a couple of pieces that had crawling after I glazed
with well lotioned hands and could almost see the fingerprints. Wearing
thin cotton gloves might work to keep hands with lotion on and not on
the pots. Then again I might be wrong and a guru might give you the
answer you are looking for.
Lori Doty
Nurse/Potter
Slowly turning the tide.
Rolla, Missouri
On Jan 14, 2006, at 1:33 PM, Judy Rohrbaugh wrote:
> I have been recently working with dipping /layering glazes. I have
> learned to not fire until everything is very dry, and for the past few
> months all has been going well.
> Now, in the past two glaze loads, I have 3-6 pots each time coming
> out with crawling near the rim, usually about 1/2 from the top.
> There is usually a total of three glazes here, both inside and out,
> all on very thin. I have managed to glaze like this for several loads
> just fine, now it's just started to happen, and I don't know why.
William & Susan Schran User on sun 15 jan 06
On 1/14/06 2:33 PM, "Judy Rohrbaugh" wrote:
> Now, in the past two glaze loads, I have 3-6 pots each time coming out with
> crawling near the rim, usually about 1/2 from the top.
> There is usually a total of three glazes here, both inside and out, all on
> very thin. I have managed to glaze like this for several loads just fine, now
> it's just started to happen, and I don't know why.
Why do glazes crawl?
Usually due to something on the bisque ware that prevents the glaze from
adhering to the clay, materials in the glaze that have high
expansion/contraction rate or simply too thick a glaze application that
cracks while drying and these cracks in the dry glaze surface may open up
when the glaze melts & shrinks.
In your instance, it appears the 3 layers of glazes are too thick and crack
on drying.
I'd suggest allowing your glazes to dry on the pots at least 24 hours prior
to loading in the kiln. Examine the pots carefully, especially where you've
seen the crawling occur, and if you see a crack wipe over that area with
your dry finger to heal it over.
CAUTION - You should do this outside and wear a respirator as you would when
weighing out the materials to mix the glaze.
-- William "Bill" Schran
Fredericksburg, Virginia
wschran@cox.net
wschran@nvcc.edu
Judy Rohrbaugh on sun 15 jan 06
Thanks. Now I am thinking. I thought I was keeping things dry enough, but perhaps not. Dry, but maybe not quite dry enough?
I don't think the glazes are too thick, there is no cracking, and I have been watching for that, although in a few spots, I guess that is still possible.
I decided that it's not dirt. I wash my bisque and let dry overnight before glazing. I always need a lot of lotion in the winter, my hands are quite chapped, but I think I am careful to not wear it when I glaze, although I could have (?) once or twice?
Thanks all. It is good to troubleshoot with help.
One more question: could a glaze crawl if it is put on too thinly? I am thinking of the glaze I use underneath. I never use it alone. It gives nice color, but never seems to stay a total 100% reliable consistency, close but not perfect to be the only glaze on the pot. I put it on first to get a solid blue color, then put another glaze on top that has copper and rultile in it for the texture/depth.
Thanks again, next load I will keep good notes, making sure it is not mositure, too thick, or lotion.
Judy Rohrbaugh
Fine Art Stoneware
Ohio
William & Susan Schran User wrote:
Why do glazes crawl?
Usually due to something on the bisque ware that prevents the glaze from
adhering to the clay, materials in the glaze that have high
expansion/contraction rate or simply too thick a glaze application that
cracks while drying and these cracks in the dry glaze surface may open up
when the glaze melts & shrinks.
In your instance, it appears the 3 layers of glazes are too thick and crack
on drying.
I'd suggest allowing your glazes to dry on the pots at least 24 hours prior
to loading in the kiln. Examine the pots carefully, especially where you've
seen the crawling occur, and if you see a crack wipe over that area with
your dry finger to heal it over.
CAUTION - You should do this outside and wear a respirator as you would when
weighing out the materials to mix the glaze.
-- William "Bill" Schran
Fredericksburg, Virginia
wschran@cox.net
wschran@nvcc.edu
______________________________________________________________________________
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.
Mildred Herot on sun 15 jan 06
Hi Judy: I don't know if anyone else does this but I put a coat of glaze on
greenware and then another coat after a bisque firing and my crawling
problems related to putting the pots in the kiln to soon. Once I stopped
that, that took care of the crawling....Mildred Herot
----- Original Message -----
From: "Judy Rohrbaugh"
To:
Sent: Sunday, January 15, 2006 4:13 PM
Subject: Re: another question on glazes crawling
> Thanks. Now I am thinking. I thought I was keeping things dry enough,
> but perhaps not. Dry, but maybe not quite dry enough?
> I don't think the glazes are too thick, there is no cracking, and I have
> been watching for that, although in a few spots, I guess that is still
> possible.
> I decided that it's not dirt. I wash my bisque and let dry overnight
> before glazing. I always need a lot of lotion in the winter, my hands are
> quite chapped, but I think I am careful to not wear it when I glaze,
> although I could have (?) once or twice?
>
> Thanks all. It is good to troubleshoot with help.
>
> One more question: could a glaze crawl if it is put on too thinly? I am
> thinking of the glaze I use underneath. I never use it alone. It gives
> nice color, but never seems to stay a total 100% reliable consistency,
> close but not perfect to be the only glaze on the pot. I put it on first
> to get a solid blue color, then put another glaze on top that has copper
> and rultile in it for the texture/depth.
> Thanks again, next load I will keep good notes, making sure it is not
> mositure, too thick, or lotion.
> Judy Rohrbaugh
> Fine Art Stoneware
> Ohio
>
> William & Susan Schran User wrote:
> Why do glazes crawl?
>
> Usually due to something on the bisque ware that prevents the glaze from
> adhering to the clay, materials in the glaze that have high
> expansion/contraction rate or simply too thick a glaze application that
> cracks while drying and these cracks in the dry glaze surface may open up
> when the glaze melts & shrinks.
>
> In your instance, it appears the 3 layers of glazes are too thick and
> crack
> on drying.
> I'd suggest allowing your glazes to dry on the pots at least 24 hours
> prior
> to loading in the kiln. Examine the pots carefully, especially where
> you've
> seen the crawling occur, and if you see a crack wipe over that area with
> your dry finger to heal it over.
> CAUTION - You should do this outside and wear a respirator as you would
> when
> weighing out the materials to mix the glaze.
>
> -- William "Bill" Schran
> Fredericksburg, Virginia
> wschran@cox.net
> wschran@nvcc.edu
>
> ______________________________________________________________________________
> 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.
>
Snail Scott on mon 16 jan 06
At 01:13 PM 1/15/2006 -0800, you wrote:
>...could a glaze crawl if it is put on too thinly? I am thinking of the
glaze I use underneath. I never use it alone...
Thin coatings seldom have trouble, even when
a thicker coating might. If you are using a
double coating, though, that may be the root
of the difficulty.
When the first layer goes on, everything is
usually fine, but when a second layer is
applied, the moisture from that second layer
can re-moisten the first layer and cause it to
expand. If this happens, it's got nowhere to
expand but outward, away from the clay. The
result can be invisible under the outer layer,
but that inner layer just isn't really stuck
on to the clay like it was, and when it starts
to melt, may not flow enough to re-cover the
unstuck areas. I think it's worst with slips,
since they melt even less and seldom re-stick
themselves, but this can happen with glazes,
too. It seems to happen most with high-clay
recipes, since they expand more when
re-wetted.
It helps to apply the second coat while the
first is still damp.
-Snail
Ruth Ballou on mon 16 jan 06
Another thought. Since you're using multiple glazes, I think you need
to look at the individual recipes. I had a glaze that never crawled
by itself, but tended to crawl badly on top of another glaze. Both
were high in alumina, though not high in clay (around 10%). One used
grolleg and the other EPK. I was able to solve it by dipping in the
second glaze before the first was dry, so that it was more like one
glaze, rather than one high alumina glaze on top of another. I might
have tried calcining part or all of the clay if that didn't work.
The fact that your crawling is occurring near the rims makes me
wonder if there isn't a thickness differential in the glaze
application. Is the rim thinner than the rest of the pot, causing the
pot to glaze to apply unevenly, thus changing the surface tension of
the glaze in that area? Sometimes the solution to these kinds of
problems involves a couple of different changes. In addition to
looking at the recipes, I would also look very carefully at the
sequence of glazing and exactly what happens at each stage, how even
the thickness of the glazes are over the total pot, and whether the
underlying glaze is dry or damp when applying the next layer. I think
it's unlikely that you're selectively getting hand lotion on the rim
only. If that were the case, the crawling should occur where ever you
might touch the pot.
Good luck!
Ruth Ballou
Belgium
On Jan 15, 2006, at 4:13 PM, Judy Rohrbaugh wrote:
> Thanks. Now I am thinking. I thought I was keeping things dry
> enough, but perhaps not. Dry, but maybe not quite dry enough?
> I don't think the glazes are too thick, there is no cracking, and
> I have been watching for that, although in a few spots, I guess
> that is still possible.
> I decided that it's not dirt. I wash my bisque and let dry
> overnight before glazing. I always need a lot of lotion in the
> winter, my hands are quite chapped, but I think I am careful to not
> wear it when I glaze, although I could have (?) once or twice?
>
> Thanks all. It is good to troubleshoot with help.
>
> One more question: could a glaze crawl if it is put on too
> thinly? I am thinking of the glaze I use underneath. I never use it
> alone. It gives nice color, but never seems to stay a total 100%
> reliable consistency, close but not perfect to be the only glaze on
> the pot. I put it on first to get a solid blue color, then put
> another glaze on top that has copper and rultile in it for the
> texture/depth.
> Thanks again, next load I will keep good notes, making sure it is
> not mositure, too thick, or lotion.
> Judy Rohrbaugh
> Fine Art Stoneware
> Ohio
>
> William & Susan Schran User wrote:
> Why do glazes crawl?
>
> Usually due to something on the bisque ware that prevents the glaze
> from
> adhering to the clay, materials in the glaze that have high
> expansion/contraction rate or simply too thick a glaze application
> that
> cracks while drying and these cracks in the dry glaze surface may
> open up
> when the glaze melts & shrinks.
>
> In your instance, it appears the 3 layers of glazes are too thick
> and crack
> on drying.
> I'd suggest allowing your glazes to dry on the pots at least 24
> hours prior
> to loading in the kiln. Examine the pots carefully, especially
> where you've
> seen the crawling occur, and if you see a crack wipe over that area
> with
> your dry finger to heal it over.
> CAUTION - You should do this outside and wear a respirator as you
> would when
> weighing out the materials to mix the glaze.
>
> -- William "Bill" Schran
> Fredericksburg, Virginia
> wschran@cox.net
> wschran@nvcc.edu
>
> ______________________________________________________________________
> ________
> 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.
>
Ron Roy on tue 17 jan 06
One of the reasons subbing in ball clay for kaolin works - the ball clay
will be much less powdery than kaolin - which gives the upper glaze
something better to hold on to.
All glazes go through some cracking as they sinter - how wide the cracks
get and how able the glaze is to heal over when melted make all the
difference.
Lichen glazes rely on light Magnesium carb - magnesium shrinks a lot as it
sinters - the more MgCO3 the more the cracking - and because magnesium
oxide has a very high viscosity and surface tension in glazes - the
cracking cannot heal over.
RR
>Thin coatings seldom have trouble, even when
>a thicker coating might. If you are using a
>double coating, though, that may be the root
>of the difficulty.
>
>When the first layer goes on, everything is
>usually fine, but when a second layer is
>applied, the moisture from that second layer
>can re-moisten the first layer and cause it to
>expand. If this happens, it's got nowhere to
>expand but outward, away from the clay. The
>result can be invisible under the outer layer,
>but that inner layer just isn't really stuck
>on to the clay like it was, and when it starts
>to melt, may not flow enough to re-cover the
>unstuck areas. I think it's worst with slips,
>since they melt even less and seldom re-stick
>themselves, but this can happen with glazes,
>too. It seems to happen most with high-clay
>recipes, since they expand more when
>re-wetted.
>
>It helps to apply the second coat while the
>first is still damp.
>
> -Snail
>
>______________________________________________________________________________
>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.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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