Earl Brunner on wed 25 may 05
I think we are both right, Lee reposted the original message as a quote in his message. It appears that Phil was talking about bubbles in the applied glaze, and if I get his drift, he seemed to think that they were related to the pinholes in the fired pots?
Steve Slatin wrote: Earl --
Maybe I misread the question! I remember it was
someone named Phil, and he mentioned that he had tried
a 20-minute soak, and the way I read it he
was referring to a glaze-after-firing flaw, but
maybe he was talking about an application issue.
The question was from someone named Phil; I can't
remember his surname. Phil, are you there? Did I
misunderstand you?
With apologies -- Steve Slatin
Earl Brunner
e-mail: brunv53@yahoo.com
Lee Love on wed 25 may 05
Steve Slatin wrote:
>The theory was that the extra bisque heat burned out
>the last of the combustibles from the clay so they
>didn't interfere with the formation of the glaze,
>
One person's "lore" is another person's "theory" it appears. ;-)
Combustibles have no effect on bubbles that appear before the glaze
firing. Common sense will tell you this much.
It is dependent upon the absorbency of the bisque, which can be
controlled by applying water with a sponge before glazing or by firing
to a higher temperature.
You can bisque at dull read heat and have absolutely no pinholing,
because I do and so does anybody who bisques in a noborigama. If you
know the factors that actually cause it, you can create it when you want
it and get rid of it when you don't. I don't want pinholing on my Nami
Jiro but I try to get it on my shinos.
When experience and theory/lore are in conflict, which should we
believe? It depends on if you value theory or if you value empirical
results more.
Of course, fast cone 6 firings are not as forgiving as longer firings.
It isn't higher temps that eliminate pinholing, because some areas of
some traditional glaze fired kilns don't get over cone 3 or 4. The
unglazed woodfired kilns frequently don't go above cone 1, but the long
firings at low temperature do more heatwork.
Another thing I have noticed that can cause pinholing (which I try to
get on my shinos) is the texture caused by trimmed surface on the lower
part of the pot, and also a large amount of kaolin in the glaze. You can
see examples of this kind of pinholing here:
Before glaze firing:
http://claycraft.blogspot.com/2005/04/this-was-low-temp-woodfired-bisque.html
After glaze firing:
http://claycraft.blogspot.com/2005/04/it-has-40-korean-kaolin.html
--
李 Lee Love 大
愛 鱗
in Mashiko, Japan http://mashiko.org
http://hankos.blogspot.com/ Visual Bookmarks
http://ikiru.blogspot.com/ Zen and Craft
"With Humans it's what's here (he points to his heart) that makes the difference. If you don't have it in the heart, nothing you make will make a difference." ~~Bernard Leach~~ (As told to Dean Schwarz)
Steve Slatin on wed 25 may 05
Lee, you're trying too hard. The pinholes don't
appear before the glaze firing, they appear in the
glaze firing. That's what the question was, and
that's what my answer replied to. The question is
why.
The proposed solution was same glaze firing ramp,
higher cone in bisque. The solution worked. That was
lore. The theory was gasses from incompletely
combusted materials in the bisqued body. Because I
don't have the equipment to test (you'd have to fire
two essentially identical pots, one to 04, one to 06,
then find a way to seal them during a firing to 6, and
test for CO and CO2 gas concentration and see if there
is a difference) I can't say I can prove that there's
a relationship. It does, however, make sense -- if a
pot distorts in bisque and I hammer it I can see with
the unaided eye the difference between the surface
clay and the clay at the center, especially if I have
a wall that's more than about 3/16 of an inch,
bisqued.
You can't compare results from wood-firing because the
length of the firing is so different. Extended glaze
firings have different characteristics on clay bodies
than shorter ones. The question was from someone using
MC6G glazes, so it's presumably someone using an
oxidation kiln firing with quicker temp changes and
shorter firings.
Again, an excellent example of how Mashiko methods are
not universal, and thanks for making my point for me.
Regards -- Steve S.
--- Lee Love wrote:
> Steve Slatin wrote:
>
> >The theory was that the extra bisque heat burned
> out
> >the last of the combustibles from the clay so they
> >didn't interfere with the formation of the glaze,
> >
> One person's "lore" is another person's "theory" it
> appears. ;-)
>
> Combustibles have no effect on bubbles that appear
> before the glaze
> firing. Common sense will tell you this much.
> It is dependent upon the absorbency of the bisque,
> which can be
> controlled by applying water with a sponge before
> glazing or by firing
> to a higher temperature.
>
> You can bisque at dull read heat and have absolutely
> no pinholing,
> because I do and so does anybody who bisques in a
> noborigama. If you
> know the factors that actually cause it, you can
> create it when you want
> it and get rid of it when you don't. I don't want
> pinholing on my Nami
> Jiro but I try to get it on my shinos.
>
> When experience and theory/lore are in conflict,
> which should we
> believe? It depends on if you value theory or if you
> value empirical
> results more.
>
> Of course, fast cone 6 firings are not as forgiving
> as longer firings.
> It isn't higher temps that eliminate pinholing,
> because some areas of
> some traditional glaze fired kilns don't get over
> cone 3 or 4. The
> unglazed woodfired kilns frequently don't go above
> cone 1, but the long
> firings at low temperature do more heatwork.
>
> Another thing I have noticed that can cause
> pinholing (which I try to
> get on my shinos) is the texture caused by trimmed
> surface on the lower
> part of the pot, and also a large amount of kaolin
> in the glaze. You can
> see examples of this kind of pinholing here:
>
> Before glaze firing:
>
>
http://claycraft.blogspot.com/2005/04/this-was-low-temp-woodfired-bisque.html
>
> After glaze firing:
>
>
http://claycraft.blogspot.com/2005/04/it-has-40-korean-kaolin.html
>
> --
> 李 Lee Love 大
> 愛 鱗
> in Mashiko, Japan http://mashiko.org
> http://hankos.blogspot.com/ Visual Bookmarks
> http://ikiru.blogspot.com/ Zen and Craft
>
> "With Humans it's what's here (he points to his
> heart) that makes the difference. If you don't have
> it in the heart, nothing you make will make a
> difference." ~~Bernard Leach~~ (As told to Dean
> Schwarz)
>
>
______________________________________________________________________________
> 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.
>
Steve Slatin --
Some men will do here for diamonds what some men will do here for gold
__________________________________________________
Do You Yahoo!?
Tired of spam? Yahoo! Mail has the best spam protection around
http://mail.yahoo.com
Earl Brunner on wed 25 may 05
Steve, I seem to remember the original message referencing bubbles or pinholes in the applied glaze. Without digging for the original, I remember thinking it was odd, because with most glazes, that doesn't much matter.
Steve Slatin wrote:Lee, you're trying too hard. The pinholes don't
appear before the glaze firing, they appear in the
glaze firing. That's what the question was, and
that's what my answer replied to. The question is
why.
Earl Brunner
e-mail: brunv53@yahoo.com
Steve Slatin on wed 25 may 05
Earl --
Maybe I misread the question! I remember it was
someone named Phil, and he mentioned that he had tried
a 20-minute soak, and the way I read it he
was referring to a glaze-after-firing flaw, but
maybe he was talking about an application issue.
The question was from someone named Phil; I can't
remember his surname. Phil, are you there? Did I
misunderstand you?
With apologies -- Steve Slatin
--- Earl Brunner wrote:
> Steve, I seem to remember the original message
> referencing bubbles or pinholes in the applied
> glaze. Without digging for the original, I remember
> thinking it was odd, because with most glazes, that
> doesn't much matter.
>
> Steve Slatin wrote:Lee,
> you're trying too hard. The pinholes don't
> appear before the glaze firing, they appear in the
> glaze firing. That's what the question was, and
> that's what my answer replied to. The question is
> why.
>
>
>
>
> Earl Brunner
> e-mail: brunv53@yahoo.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.
>
Steve Slatin --
Some men will do here for diamonds what some men will do here for gold
__________________________________________________
Do You Yahoo!?
Tired of spam? Yahoo! Mail has the best spam protection around
http://mail.yahoo.com
Ann Brink on thu 26 may 05
Hi Phil,
I have found that it's helpful to have my glazes rather thinly mixed, and
hold the pieces in longer, rather than have the glaze thicker and immersing
the pieces very quickly. My logic here is that a thin glaze can get into
the "pores" of the clay more readily than a thick glaze.
One person wrote in that she dunks the pot first; I think this promotes
wicking of the glaze to the pot. I do this sometimes too, but am careful to
quickly set the pot upright, to let the rims dry a bit before glazing,
otherwise not enough glaze will adhere to any very smooth rims.
Ann Brink in Lompoc CA- finishing a glaze firing, with some tests in it I'm
eager to see. (So what's new?)
Phil wrote:> I am seeing pin holes at two stages of the glazing process----
>
> 1. After I have glazed the pot (the pot is either dipped or the glaze
> is poured) small pin holes appear in the dried glaze. I will use my
> finger like a piece of sandpaper and rub the surface of the pot. This
> does appear to eliminate the pin holes (I think).
>
> 2. The second time I see pinholes is after the pots have been glaze
> fired. They vary in size and location. A lot of them appear in the
> trimmed section of each piece. Others appear at any location.
> Presently I am doing a 20 minute soak, at the end of the firing. I am
> not doing a ramp firing.
>
>
> Some of the pieces have been bisque fired to cone 04 and others at 06.
> I usually do the 04 firing but have recently gone down to 06. I think I
> will go back to 04 and see if that eliminates some of the problem.
>
> I try and not handle the bisque ware, much, because of body oils. I
> also do a damp sponge wash just before I glaze each piece.
>
> Thanks for the help and I hope my answers clear up some of the
> misunderstandings.
>
> Phil Davenport
Chris Schafale on thu 26 may 05
For pinholes in the trimmed areas, here is a solution that works well for
me. After trimming, I take a wide paintbrush and brush thin slip from the
upper layers of my throwing bucket over the trimmed area with the wheel
turning. I then take a flexible rubber rib and smooth over it, again with
the wheel turning, removing the excess slip. This fills in the grog
scratches and the little holes that seem to be revealed when you remove the
clay's "skin" during trimming. Since doing this I have many fewer pinholes
in these areas of my pots, and if I forget, I see the results after
glazing. Hope this helps.
Chris
At 10:51 AM 05/26/2005, you wrote:
>I am seeing pin holes at two stages of the glazing process----
>
>1. After I have glazed the pot (the pot is either dipped or the glaze
>is poured) small pin holes appear in the dried glaze. I will use my
>finger like a piece of sandpaper and rub the surface of the pot. This
>does appear to eliminate the pin holes (I think).
>
>2. The second time I see pinholes is after the pots have been glaze
>fired. They vary in size and location. A lot of them appear in the
>trimmed section of each piece. Others appear at any location.
>Presently I am doing a 20 minute soak, at the end of the firing. I am
>not doing a ramp firing.
Jean Cochran on thu 26 may 05
Hi Folks,
Talking about pin holing, For many years I have known to clean my pots with
water before glazing. However, only in the last two or three firings, I
have begun dipping each pot in a vat of water, waiting a couple of instances
and then dipping immediately in the glaze. What a huge difference. Just
when I think I know something, I find out that I do not know it after all.
Jean Wadsworth Cochran
www.foxhollowpottery.com
www.kycraft.ky.gov/craftcgi-bin/index.cgi?busid=186
Earl Brunner on thu 26 may 05
I admit, as I was writing the reply below, the one glaze that I thought of that I felt might do this was shino. Shinos don't move much at all. I suspect that other glazes which are sensitive to thickness, might as well. Glad to see you verify that thought.
Lee Love wrote:Earl Brunner wrote:
>I think that one of the problems is that the bubbles you see in dipped glaze probably have little or no bearing on the pinholing you are seeing in the fired glaze. At least i know that is the case with most of the glazes I fire. Most of the glazes I use flow enough that any bubbles in the application will smooth out during the melt.
>
>
Trust me, they can be related, because I was taken to task when ever
pinholes appeared after the firing at my teacher's workshop. Rubbing the
bubbles out are not the best way to get rid of them, because you are
also thinning the glaze at that spot. It is better to take a small brush
and dab the pinholes.
Here is an example of glaze application pinholing that results in
pinholing after the firing. In Japan, pinholing and crawling in glazes
like shino is desireable, so it is good to know how to make it happen.
Hi kaolin in the glaze seems to help as well as a low temp bisque. Also
note that the glaze is very clear and has absolutely no carbon trapping.
Please look and see for yourself:
Glaze just applied:
http://claycraft.blogspot.com/2005/04/this-was-low-temp-woodfired-bisque.html
Same pot fired:
http://claycraft.blogspot.com/2005/04/desired-pinholing.html
Earl Brunner
e-mail: brunv53@yahoo.com
Phil Davenport on thu 26 may 05
I am seeing pin holes at two stages of the glazing process----
1. After I have glazed the pot (the pot is either dipped or the glaze
is poured) small pin holes appear in the dried glaze. I will use my
finger like a piece of sandpaper and rub the surface of the pot. This
does appear to eliminate the pin holes (I think).
2. The second time I see pinholes is after the pots have been glaze
fired. They vary in size and location. A lot of them appear in the
trimmed section of each piece. Others appear at any location.
Presently I am doing a 20 minute soak, at the end of the firing. I am
not doing a ramp firing.
Some of the pieces have been bisque fired to cone 04 and others at 06.
I usually do the 04 firing but have recently gone down to 06. I think I
will go back to 04 and see if that eliminates some of the problem.
I try and not handle the bisque ware, much, because of body oils. I
also do a damp sponge wash just before I glaze each piece.
Thanks for the help and I hope my answers clear up some of the
misunderstandings.
Phil Davenport
Garland, Tx.
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Steve
Slatin
Sent: Wednesday, May 25, 2005 8:12 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Pinholing after Glazing.
Earl --
Maybe I misread the question! I remember it was
someone named Phil, and he mentioned that he had tried
a 20-minute soak, and the way I read it he
was referring to a glaze-after-firing flaw, but
maybe he was talking about an application issue.
The question was from someone named Phil; I can't
remember his surname. Phil, are you there? Did I
misunderstand you?
Jeanette Harris on thu 26 may 05
>>
>Rubbing them out often does not get rid of the pinholes.. I know from
>preparing for glazing 10s of thousands of low bisqued pots at my
>teacher's workshop. I would get admonished anytime pinholes appeared
>after glazing . At first, I was told to wash my hands, because
>frequently, the cause was oil on someone's hands. After the first couple
>times, I would just get up and wash my hands with soap when ever
>pinholes appeared before I started wiping again, before anybody could
>say anything.
Wearing surgical gloves while glazing works too. You can get the
lightweight ones in bulk.
Better for your skin too.
I do a quick dip of each piece in a bucket of water. Let it sit a
couple of hours and then glaze. I don't use thin glaze--mine's a bit
thicker--but that method works for me.
--
Jeanette Harris
Poulsbo WA
Potter's Council member
Earl Brunner on thu 26 may 05
I think that one of the problems is that the bubbles you see in dipped glaze probably have little or no bearing on the pinholing you are seeing in the fired glaze. At least i know that is the case with most of the glazes I fire. Most of the glazes I use flow enough that any bubbles in the application will smooth out during the melt.
>>
>Rubbing them out often does not get rid of the pinholes.. I know from
>preparing for glazing 10s of thousands of low bisqued pots at my
>teacher's workshop. I would get admonished anytime pinholes appeared
>after glazing . At first, I was told to wash my hands, because
>frequently, the cause was oil on someone's hands. After the first couple
>times, I would just get up and wash my hands with soap when ever
>pinholes appeared before I started wiping again, before anybody could
>say anything.
Earl Brunner
e-mail: brunv53@yahoo.com
Lee Love on thu 26 may 05
Earl Brunner wrote:
>Steve, I seem to remember the original message referencing bubbles or pinholes in the applied glaze. Without digging for the original, I remember thinking it was odd, because with most glazes, that doesn't much matter.
>
You are right Earl. Here is the original:
> Phil Davenport wrote:
>
>I have done some testing of the glazes listed in the Mastering Cone 6
>book and am seeing a couple of problems. One is pin holes. I am doing
>a 20 minutes soak. Should I go longer? Is anyone else having this
>problem?
>
>I noticed some pin holes, as the glaze dried, and rubbed those areas
>with my finger.
>
>
Rubbing them out often does not get rid of the pinholes.. I know from
preparing for glazing 10s of thousands of low bisqued pots at my
teacher's workshop. I would get admonished anytime pinholes appeared
after glazing . At first, I was told to wash my hands, because
frequently, the cause was oil on someone's hands. After the first couple
times, I would just get up and wash my hands with soap when ever
pinholes appeared before I started wiping again, before anybody could
say anything. Also, we were not allowed to used any kind of hand cream
while we were glazing, because it would cause pinholing on the bisqued
surface. Eating something like potato chips at tea break was also a
hazard.. Also, water that comes from wiping glaze spots on wax resisted
surfaces is never used to sponge bisque before glazing, because the
kerosene in the resist will also cause resisiting and/or pinholing on
the bisque.
Phil's other problem was:
>None of my test pieces had the bare spots and I was doing the 20 minute
>soak. About the only difference is the thickness of the glazes. When
>doing the initial testing the glazes were thicker. Since then I have
>added additional water to the glazes.
>
Glaze thickness may have cause the thin spots on the rims of larger
work. There is no way to attribute this to the firing schedual, unless
it was at a much higher temperature than the test..
I have found that the single biggest difference between test tiles and
putting a new glaze on a whole pot is the difference in thickness
between the small test tile and the larger pot.
Sometimes, when your only tool is a hammer all problems look like nails.
;-)
--
李 Lee Love 大
愛 鱗
in Mashiko, Japan http://mashiko.org
http://hankos.blogspot.com/ Visual Bookmarks
http://ikiru.blogspot.com/ Zen and Craft
"With Humans it's what's here (he points to his heart) that makes the difference. If you don't have it in the heart, nothing you make will make a difference." ~~Bernard Leach~~ (As told to Dean Schwarz)
Lee Love on fri 27 may 05
Earl Brunner wrote:
>I think that one of the problems is that the bubbles you see in dipped glaze probably have little or no bearing on the pinholing you are seeing in the fired glaze. At least i know that is the case with most of the glazes I fire. Most of the glazes I use flow enough that any bubbles in the application will smooth out during the melt.
>
>
Trust me, they can be related, because I was taken to task when ever
pinholes appeared after the firing at my teacher's workshop. Rubbing the
bubbles out are not the best way to get rid of them, because you are
also thinning the glaze at that spot. It is better to take a small brush
and dab the pinholes.
Here is an example of glaze application pinholing that results in
pinholing after the firing. In Japan, pinholing and crawling in glazes
like shino is desireable, so it is good to know how to make it happen.
Hi kaolin in the glaze seems to help as well as a low temp bisque. Also
note that the glaze is very clear and has absolutely no carbon trapping.
Please look and see for yourself:
Glaze just applied:
http://claycraft.blogspot.com/2005/04/this-was-low-temp-woodfired-bisque.html
Same pot fired:
http://claycraft.blogspot.com/2005/04/desired-pinholing.html
--
李 Lee Love 大
愛 鱗
in Mashiko, Japan http://mashiko.org
http://hankos.blogspot.com/ Visual Bookmarks
http://ikiru.blogspot.com/ Zen and Craft
"With Humans it's what's here (he points to his heart) that makes the difference. If you don't have it in the heart, nothing you make will make a difference." ~~Bernard Leach~~ (As told to Dean Schwarz)
claybair on sat 28 may 05
Jean,
I used to wipe down my bisque with a damp sponge
which became laborious when I was doing production pieces.
So I also started dipping the pieces in water.
All was well until II noticed on some of the pieces
the glaze application seemed too thin.
The cause had several possibilities:
Too long a dip in water
1.The piece was too thin and absorbed more water than glaze
2.The time held in the glaze was too short
3.Thickness of the glaze needed adjusting
My bisque now gets a very quick a water dip.
Thin pieces may get put out in the sun before glazing.
Gayle Bair
Bainbridge Island, WA
Tucson, AZ
http://claybair.com
-----Original Message-----
From:Jean Cochran
Talking about pin holing, For many years I have known to clean my pots with
water before glazing. However, only in the last two or three firings, I
have begun dipping each pot in a vat of water, waiting a couple of instances
and then dipping immediately in the glaze. What a huge difference. Just
when I think I know something, I find out that I do not know it after all.
--
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.322 / Virus Database: 267.1.0 - Release Date: 5/27/2005
dalecochoy on fri 3 jun 05
This thread ( below) got me thinking about the ( at least "MY") ongoing
problem with Standard #266. A while back, maybe two years, I complained
about getting serious bloating on larger 266 pots. I ruined so much work I
threw out the clay I had left. People suggested bisqueing to 04 from 05
which I do always now with everything, and bisqueing/firing slower ( no one
does either slower than me BTW) and not firing it to cone 6 ( still bloated
at cone 5)
Anyway, I didn't use any for some time then decided to try a box again.
Whatever they changed seemed to fix the bloating problem? I don't get ANY at
any size/thickness of pot now, but,.....
EVERY, I repeat EVERY glaze I use on it will pinhole ( bubble) usually near
the top of pot. Always, every glazed pot. Now usually I don't mind a bit on
bonsai pots but some are really bad.
Gosh, I wish they'd thoroughly test this clay some more. Great color for my
uses but forget glazing it.
Regards,
Dale
----- Original Message -----
From: "Steve Slatin"
Subject: Re: Pinholing after Glazing.
>
> The proposed solution was same glaze firing ramp,
> higher cone in bisque. The solution worked. That was
> lore. The theory was gasses from incompletely
> combusted materials in the bisqued body. Because I
> don't have the equipment to test (you'd have to fire
> two essentially identical pots, one to 04, one to 06,
> then find a way to seal them during a firing to 6, and
> test for CO and CO2 gas concentration and see if there
> is a difference) I can't say I can prove that there's
> a relationship. It does, however, make sense -- if a
> pot distorts in bisque and I hammer it I can see with
> the unaided eye the difference between the surface
> clay and the clay at the center, especially if I have
> a wall that's more than about 3/16 of an inch,
> bisqued.
>
| |
|
