[Clayart] Healing blisters and pinholes
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Robert L. Johnson
Jul 15, 2022, 7:39:30 PM7/15/22
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Does overfiring cause pinholes and blisters? And can firing a little hotter
heal them?
heal them?
Occasionally my gas kiln gets out of control, and cone 7 goes down when I’m
targeting cone 6. Inevitably, I get blisters and pinholes. But the reason I
ask is that I was talking to another potter who uses many of the same
glazes and combinations that I do (Ron’s Mastering Cone Six Glazes and
Steven Hill’s cone 6 recipes), and she said she takes the same glazes all
up to cone 8 and the blisters and holes heal over.
Is she crazy? Is it possible that firing cone 6 glazes to cone 7 causes
blisters but firing a little hotter can heal them?
I don’t want to waste a kiln load if someone already knows the answer!
Thanks!
Bob in Southern Oregon
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David Woof
Jul 16, 2022, 9:13:05 AM7/16/22
to Clayart international pottery discussion forum
Hi Bob, all I know for sure is that I get perfect results by firing a Family of glazes I've developed from the same base glaze so that all mature at the same cone bending position and thus are all compatible with each other.
Combining or overlapping Glaze recipes on the same pot, from different sources that vary too much in Maturation rate (heat-work) and a compounding of divergent raw materials and fluxes cause fluxing eutectics to form during the firing and this opens the door for all sorts of crazy "bleep" to happen.
If I let it happen, I could let it drive me nuts to hear folks say: " I fire my cone 5 glazes to cone 6." Or I fire my ^6 glaze to ^7 or ^8 etc. etc.
Then isn't it logical that what they really have is a cone 7 or 8 glaze? For the "terminally unique" folks this idea seems to gain traction and a modicum of self-congratulatory fame of "I Did It My Way"
Just like we discuss the foolishness of claims for a ^6 to ^10 clay body. Isn't it equally stupid to claim a glaze as truly "broad range?" Is a person ever "kinda pregnant?" One either is or isn't. Right?
Bob, you ask "is this woman crazy?" I think that would be for you to decide after you take Ron and John's glazes (no one else's for this test) and fire a load until Large cone 6 touches its tip on the shelf with no subsequent soak hold. Then shut down, or crash Drop the firing down to 1900f and hold several hours at 1900f before shutting down. You can get more experimental after you have Mastered Ron and John's Cone 6 Glazes.
Read and understand their whole book.
Don't just copy a recipe from them and shoot from the hip. They state that all of their glazes in the book were formulated and tested to mature at Large cone 6 with tip just touching the shelf.
Baby sit your kiln, watch the cones. Let the kiln "go wild" as you say because nothing matters at this point except what the cones indicate as far as "heat work." You can fine tune the kiln later.
***Right now, apply heat and watch the cones.
I could go on and on about overfired/underfired, blistering and pinholes, and healed pinholes, and devitrified glazes etc. etc. but I've watched you struggle with these issues for a number of years and the advice I feel to offer is that you need to back up and start with applying the basics found in Ron and John's "Mastering Cone 6 Glazes."
For all the difficulties you've expressed....You don't give up! And I respect you deeply for that.
If you ever come over to Myrtle Point or Bandon by the Sea, please consider this an invitation to come sit by my fire awhile.
Misneach,
David Woof..........................................................................................................................................
************************************************************************************
________________________________
From: Clayart <clayart...@lists.clayartworld.com> on behalf of Robert L. Johnson <impal...@gmail.com>
Sent: Friday, July 15, 2022 2:20 PM
To: cla...@lists.clayartworld.com <cla...@lists.clayartworld.com>
Subject: [Clayart] Healing blisters and pinholes
URL: <https://lists.clayartworld.com/pipermail/clayart/attachments/20220716/ab6c77e8/attachment.htm>
Combining or overlapping Glaze recipes on the same pot, from different sources that vary too much in Maturation rate (heat-work) and a compounding of divergent raw materials and fluxes cause fluxing eutectics to form during the firing and this opens the door for all sorts of crazy "bleep" to happen.
If I let it happen, I could let it drive me nuts to hear folks say: " I fire my cone 5 glazes to cone 6." Or I fire my ^6 glaze to ^7 or ^8 etc. etc.
Then isn't it logical that what they really have is a cone 7 or 8 glaze? For the "terminally unique" folks this idea seems to gain traction and a modicum of self-congratulatory fame of "I Did It My Way"
Just like we discuss the foolishness of claims for a ^6 to ^10 clay body. Isn't it equally stupid to claim a glaze as truly "broad range?" Is a person ever "kinda pregnant?" One either is or isn't. Right?
Bob, you ask "is this woman crazy?" I think that would be for you to decide after you take Ron and John's glazes (no one else's for this test) and fire a load until Large cone 6 touches its tip on the shelf with no subsequent soak hold. Then shut down, or crash Drop the firing down to 1900f and hold several hours at 1900f before shutting down. You can get more experimental after you have Mastered Ron and John's Cone 6 Glazes.
Read and understand their whole book.
Don't just copy a recipe from them and shoot from the hip. They state that all of their glazes in the book were formulated and tested to mature at Large cone 6 with tip just touching the shelf.
Baby sit your kiln, watch the cones. Let the kiln "go wild" as you say because nothing matters at this point except what the cones indicate as far as "heat work." You can fine tune the kiln later.
***Right now, apply heat and watch the cones.
I could go on and on about overfired/underfired, blistering and pinholes, and healed pinholes, and devitrified glazes etc. etc. but I've watched you struggle with these issues for a number of years and the advice I feel to offer is that you need to back up and start with applying the basics found in Ron and John's "Mastering Cone 6 Glazes."
For all the difficulties you've expressed....You don't give up! And I respect you deeply for that.
If you ever come over to Myrtle Point or Bandon by the Sea, please consider this an invitation to come sit by my fire awhile.
Misneach,
David Woof..........................................................................................................................................
************************************************************************************
________________________________
From: Clayart <clayart...@lists.clayartworld.com> on behalf of Robert L. Johnson <impal...@gmail.com>
Sent: Friday, July 15, 2022 2:20 PM
To: cla...@lists.clayartworld.com <cla...@lists.clayartworld.com>
Subject: [Clayart] Healing blisters and pinholes
ron...@ca.inter.net
Jul 16, 2022, 1:31:09 PM7/16/22
to Clayart international pottery discussion forum, Robert L. Johnson, cla...@lists.clayartworld.com
Hi Bob,
Sounds like your clay is breaking down because it is over fired. This
causes gas release that results in blisters and pinholes.
If you are using an iron bearing clay it might also be because you are
not firing your bisque in excess oxygen or too fast or not high enough
to burn out any carbonaceous material.
There are ways to deal with some of the causes but if the clay cannot
stand overfiring you may have to change clays.
All that said - why are you not there watching your cones fall?
RR
Quoting "Robert L. Johnson" <impal...@gmail.com>:
> Does overfiring cause pinholes and blisters? And can firing a little hotter
> heal them?
>
> Occasionally my gas kiln gets out of control, and cone 7 goes down when I?m
> Steven Hill?s cone 6 recipes), and she said she takes the same glazes all
ron...@ca.inter.net
Web page ronroy.net
Sounds like your clay is breaking down because it is over fired. This
causes gas release that results in blisters and pinholes.
If you are using an iron bearing clay it might also be because you are
not firing your bisque in excess oxygen or too fast or not high enough
to burn out any carbonaceous material.
There are ways to deal with some of the causes but if the clay cannot
stand overfiring you may have to change clays.
All that said - why are you not there watching your cones fall?
RR
Quoting "Robert L. Johnson" <impal...@gmail.com>:
> Does overfiring cause pinholes and blisters? And can firing a little hotter
> heal them?
>
> targeting cone 6. Inevitably, I get blisters and pinholes. But the reason I
> ask is that I was talking to another potter who uses many of the same
> glazes and combinations that I do (Ron?s Mastering Cone Six Glazes and
> ask is that I was talking to another potter who uses many of the same
> Steven Hill?s cone 6 recipes), and she said she takes the same glazes all
> up to cone 8 and the blisters and holes heal over.
> Is she crazy? Is it possible that firing cone 6 glazes to cone 7 causes
> blisters but firing a little hotter can heal them?
> I don?t want to waste a kiln load if someone already knows the answer!
> Is she crazy? Is it possible that firing cone 6 glazes to cone 7 causes
> blisters but firing a little hotter can heal them?
> Thanks!
> Bob in Southern Oregon
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Ron Roy
> Bob in Southern Oregon
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ron...@ca.inter.net
Web page ronroy.net
Robert L. Johnson
Jul 18, 2022, 1:22:21 PM7/18/22
to cla...@lists.clayartworld.com
Well, Ron, you are going to make me confess a ceramic sin: I use a cone
9-10 B-mix knock-off at cone 6 because I don't like the cone 5-6
version--and the cone 10 clay seems to work pretty well. I suppose therein
could lie another problem. Anyway, I don't think the clay is overfired.
As for not watching my cones: I usually am right there at the right time,
but the last time it happened it was a "dumb user" issue, when I thought I
had 20 minutes to go, cone 6 had not started bending, and so I went back
into the house for a cup of coffee; upon returning to the kiln, cone 7 was
down.
Now you know most of my secrets, but I'm still puzzled about whether firing
up one more cone might heal those blisters. Mel helped about a year ago
with some advice about heat dams I was creating, but I think I solved that
problem.
9-10 B-mix knock-off at cone 6 because I don't like the cone 5-6
version--and the cone 10 clay seems to work pretty well. I suppose therein
could lie another problem. Anyway, I don't think the clay is overfired.
As for not watching my cones: I usually am right there at the right time,
but the last time it happened it was a "dumb user" issue, when I thought I
had 20 minutes to go, cone 6 had not started bending, and so I went back
into the house for a cup of coffee; upon returning to the kiln, cone 7 was
down.
Now you know most of my secrets, but I'm still puzzled about whether firing
up one more cone might heal those blisters. Mel helped about a year ago
with some advice about heat dams I was creating, but I think I solved that
problem.
Bob - with blisters and pinholes in Roseburg, Oregon
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David Woof
Jul 19, 2022, 7:25:22 AM7/19/22
to Clayart international pottery discussion forum, Robert L. Johnson
Bob asks us for advice regarding his "glaze problems" and then sez: < "Anyway, I don't think the clay is overfired.">
Wa-wa-What????
Bob, It seems that Blisters and Pin holes may be the least of your problems.
Ron had just posted his usual well considered advice and by your response you indicate that you are unable to understand much less to follow it.
I too wrote to you, giving time proven advice and suggested that you stop and back up in your apparent headlong rush to gather ever increasing difficulties.
I suggested that you first study Ron and John's "Mastering Cone 6 Glazes" text until you understand.
Studying the book first, rather than as you did, taking one glaze recipe from their book and then firing it on the advice of a supposed potter of whom you ask:<"is she Crazy?">
What does "Mastering Cone 6 Glazes" mean to you? " M-a-s-t-e-r-i-n-g "
I have no personal or monetary stake in promoting Ron and John, or their Book.
But because I highly respect their work, I have tested what they say and so I feel confident in recommending.
Though trusting him, I even tested substitutes for Ron's "cone 6 light colored body" formula just to see how a substitution could change the absorption percentage.
***Ron's cone 6 body stands good to go.
Why are you messing around with a ^8 -10 B-Mix knock off for ^6 firing. What part don't you get!!!
I would use Ron's Clay Body except I had already developed my own cone 6 white that has a stable 0.4 absorption % at large cone 6, tip down to the shelf.
Applied on my ^6 body, my glazes, formulated and tested to mature and not run, pit, or overfire at the
same ^ 6 position of tip touching the shelf, my face grins and my heart sings. (Skills Pay the Bills)
You can bet that I don't go for coffee or get on the phone when Cone 6 is softening and about to move.
***FYI. I post information for folks with enough humility (teachableness) to be willing to try something new when their old way presents difficulties or is more time consuming.
From your past history of failing to implement sound direction and advice, I don't write to you alone, but post for others who may appreciate and understand the value.
Because you'll probably think I'm peeing in your pablum, and Rox will probably call me a "Bully," I will consider this post a job accompli and go now to have good times with sensible people who know me, love me, and seek my company.
Much love and a Hope for a better time to come soon,
Woof....................................A much needed rebuke from someone who cares is an act of love...Tho it may sting..............
To: cla...@lists.clayartworld.com <cla...@lists.clayartworld.com>
Subject: Re: [Clayart] Healing blisters and pinholes
URL: <https://lists.clayartworld.com/pipermail/clayart/attachments/20220719/366d1835/attachment.htm>
Wa-wa-What????
Bob, It seems that Blisters and Pin holes may be the least of your problems.
Ron had just posted his usual well considered advice and by your response you indicate that you are unable to understand much less to follow it.
I too wrote to you, giving time proven advice and suggested that you stop and back up in your apparent headlong rush to gather ever increasing difficulties.
I suggested that you first study Ron and John's "Mastering Cone 6 Glazes" text until you understand.
Studying the book first, rather than as you did, taking one glaze recipe from their book and then firing it on the advice of a supposed potter of whom you ask:<"is she Crazy?">
What does "Mastering Cone 6 Glazes" mean to you? " M-a-s-t-e-r-i-n-g "
I have no personal or monetary stake in promoting Ron and John, or their Book.
But because I highly respect their work, I have tested what they say and so I feel confident in recommending.
Though trusting him, I even tested substitutes for Ron's "cone 6 light colored body" formula just to see how a substitution could change the absorption percentage.
***Ron's cone 6 body stands good to go.
Why are you messing around with a ^8 -10 B-Mix knock off for ^6 firing. What part don't you get!!!
I would use Ron's Clay Body except I had already developed my own cone 6 white that has a stable 0.4 absorption % at large cone 6, tip down to the shelf.
Applied on my ^6 body, my glazes, formulated and tested to mature and not run, pit, or overfire at the
same ^ 6 position of tip touching the shelf, my face grins and my heart sings. (Skills Pay the Bills)
You can bet that I don't go for coffee or get on the phone when Cone 6 is softening and about to move.
***FYI. I post information for folks with enough humility (teachableness) to be willing to try something new when their old way presents difficulties or is more time consuming.
From your past history of failing to implement sound direction and advice, I don't write to you alone, but post for others who may appreciate and understand the value.
Because you'll probably think I'm peeing in your pablum, and Rox will probably call me a "Bully," I will consider this post a job accompli and go now to have good times with sensible people who know me, love me, and seek my company.
Much love and a Hope for a better time to come soon,
Woof....................................A much needed rebuke from someone who cares is an act of love...Tho it may sting..............
________________________________
From: Clayart <clayart...@lists.clayartworld.com> on behalf of Robert L. Johnson <impal...@gmail.com>
Sent: Sunday, July 17, 2022 11:47 PM
From: Clayart <clayart...@lists.clayartworld.com> on behalf of Robert L. Johnson <impal...@gmail.com>
To: cla...@lists.clayartworld.com <cla...@lists.clayartworld.com>
Subject: Re: [Clayart] Healing blisters and pinholes
ka...@lesueurclaywork.com
Jul 19, 2022, 2:30:24 PM7/19/22
to Clayart international pottery discussion forum
Sometimes just a simple ingredient change can solve a problem. I had a glaze that bubbled and pitted, especially on the hip of a vase. Nothing worked to stop it. But the, I got a recipe for a glaze that used C&C ball clay instead of OM4. I decided to replace the OM4 in my troubled glaze with C&C ball. Problem solved.
Kathi LeSueur
Sent from my iPad
> On Jul 19, 2022, at 7:25 AM, David Woof <woof...@hotmail.com> wrote:
>
> Bob asks us for advice regarding his "glaze problems" and then sez: < "Anyway, I don't think the clay is overfired.">
Kathi LeSueur
Sent from my iPad
> On Jul 19, 2022, at 7:25 AM, David Woof <woof...@hotmail.com> wrote:
>
> Bob asks us for advice regarding his "glaze problems" and then sez: < "Anyway, I don't think the clay is overfired.">
Snail Scott
Jul 20, 2022, 7:31:30 AM7/20/22
to Clayart international pottery discussion forum
> On Jul 15, 2022, at 3:20 PM, Robert L. Johnson <impal...@gmail.com> wrote:
> Is it possible that firing cone 6 glazes to cone 7 causes
> blisters but firing a little hotter can heal them?
-Snail
David Woof
Jul 20, 2022, 7:32:37 AM7/20/22
to Clayart international pottery discussion forum
HI Kathi,
Yes to C&C which I'm sure you know is an engineered product that eliminates several troubling variances we encounter when using more or less straight from the mine clays.
A couple good engineered for consistency feldspars for the long term would also be worth the efforts to obtain.
Or get us back to the old PV clay that the old man provided while he was still running the mine.
Ooops I better head off a Rant before I get one started. I loved PV because I could get the Potassium I needed, w/o shortening the body with a Potash Feldspar.
Oh but one must adjust for life altering changes...........Haaaaa!!!
David.........................................................................................................................................
*********************************************************************************
________________________________
From: Clayart <clayart...@lists.clayartworld.com> on behalf of ka...@lesueurclaywork.com <ka...@lesueurclaywork.com>
Sent: Tuesday, July 19, 2022 7:13 AM
To: Clayart international pottery discussion forum <cla...@lists.clayartworld.com>
URL: <https://lists.clayartworld.com/pipermail/clayart/attachments/20220720/29f5277c/attachment.htm>
Yes to C&C which I'm sure you know is an engineered product that eliminates several troubling variances we encounter when using more or less straight from the mine clays.
A couple good engineered for consistency feldspars for the long term would also be worth the efforts to obtain.
Or get us back to the old PV clay that the old man provided while he was still running the mine.
Ooops I better head off a Rant before I get one started. I loved PV because I could get the Potassium I needed, w/o shortening the body with a Potash Feldspar.
Oh but one must adjust for life altering changes...........Haaaaa!!!
David.........................................................................................................................................
*********************************************************************************
________________________________
From: Clayart <clayart...@lists.clayartworld.com> on behalf of ka...@lesueurclaywork.com <ka...@lesueurclaywork.com>
Sent: Tuesday, July 19, 2022 7:13 AM
To: Clayart international pottery discussion forum <cla...@lists.clayartworld.com>
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