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#1 Min

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Posted 04 February 2013 - 11:49 AM

I am having an issue with one of the glazes I use not sealing the clay when fired to maturity. I use a ^6 claybody, Georgies White Salmon, firing to cone 6, tip of cone touching the shelf and the glaze that leads to weeping pots is Licorice from MC6Glazes. I have tried firing hotter (cone 7 tip nearly touching shelf) and the pots seep less but it's still an issue. To test for seeping I placed a glazed pot filled with water on newsprint and left it sit for 48 hours. Paper was wrinkled under the pot. Have tested several pots and they all weeped. The absorption was under 2 percent when I did a boil and weigh test of fired clay so I don't think it's an issue with the claybody, also, my other glazes don't have seepage problems. Anyone have any ideas how to fix this glaze? Thanks in advance for any help.

#2 OffCenter

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Posted 04 February 2013 - 01:21 PM

I am having an issue with one of the glazes I use not sealing the clay when fired to maturity. I use a ^6 claybody, Georgies White Salmon, firing to cone 6, tip of cone touching the shelf and the glaze that leads to weeping pots is Licorice from MC6Glazes. I have tried firing hotter (cone 7 tip nearly touching shelf) and the pots seep less but it's still an issue. To test for seeping I placed a glazed pot filled with water on newsprint and left it sit for 48 hours. Paper was wrinkled under the pot. Have tested several pots and they all weeped. The absorption was under 2 percent when I did a boil and weigh test of fired clay so I don't think it's an issue with the claybody, also, my other glazes don't have seepage problems. Anyone have any ideas how to fix this glaze? Thanks in advance for any help.


You are not having an issue with a glaze. You have a problem with a leaking clay body. You should not try to "seal" a pot with glaze. The test you did should have been done with an UNGLAZED pot. Almost always, glazing will not stop a clay from leaking and you shouldn't make any pot meant to hold a liquid unless an unglazed cylinder of it does not leak overnight on paper. (Even a slight dampness is leaking.) Sometimes it takes getting sued for a vase leaking on a grand piano for a potter to learn that they shouldn't sell leaking pots.

Switch to a ^6 clay that doesn't leak. B-Mix 5 is just one of many white clay bodies that don't leak when fired to cone 6.

Jim
E pur si muove.

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#3 Min

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Posted 04 February 2013 - 03:43 PM


I am having an issue with one of the glazes I use not sealing the clay when fired to maturity. I use a ^6 claybody, Georgies White Salmon, firing to cone 6, tip of cone touching the shelf and the glaze that leads to weeping pots is Licorice from MC6Glazes. I have tried firing hotter (cone 7 tip nearly touching shelf) and the pots seep less but it's still an issue. To test for seeping I placed a glazed pot filled with water on newsprint and left it sit for 48 hours. Paper was wrinkled under the pot. Have tested several pots and they all weeped. The absorption was under 2 percent when I did a boil and weigh test of fired clay so I don't think it's an issue with the claybody, also, my other glazes don't have seepage problems. Anyone have any ideas how to fix this glaze? Thanks in advance for any help.


You are not having an issue with a glaze. You have a problem with a leaking clay body. You should not try to "seal" a pot with glaze. The test you did should have been done with an UNGLAZED pot. Almost always, glazing will not stop a clay from leaking and you shouldn't make any pot meant to hold a liquid unless an unglazed cylinder of it does not leak overnight on paper. (Even a slight dampness is leaking.) Sometimes it takes getting sued for a vase leaking on a grand piano for a potter to learn that they shouldn't sell leaking pots.

Switch to a ^6 clay that doesn't leak. B-Mix 5 is just one of many white clay bodies that don't leak when fired to cone 6.

Jim



#4 Min

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Posted 04 February 2013 - 04:04 PM



I am having an issue with one of the glazes I use not sealing the clay when fired to maturity. I use a ^6 claybody, Georgies White Salmon, firing to cone 6, tip of cone touching the shelf and the glaze that leads to weeping pots is Licorice from MC6Glazes. I have tried firing hotter (cone 7 tip nearly touching shelf) and the pots seep less but it's still an issue. To test for seeping I placed a glazed pot filled with water on newsprint and left it sit for 48 hours. Paper was wrinkled under the pot. Have tested several pots and they all weeped. The absorption was under 2 percent when I did a boil and weigh test of fired clay so I don't think it's an issue with the claybody, also, my other glazes don't have seepage problems. Anyone have any ideas how to fix this glaze? Thanks in advance for any help.


You are not having an issue with a glaze. You have a problem with a leaking clay body. You should not try to "seal" a pot with glaze. The test you did should have been done with an UNGLAZED pot. Almost always, glazing will not stop a clay from leaking and you shouldn't make any pot meant to hold a liquid unless an unglazed cylinder of it does not leak overnight on paper. (Even a slight dampness is leaking.) Sometimes it takes getting sued for a vase leaking on a grand piano for a potter to learn that they shouldn't sell leaking pots.

Switch to a ^6 clay that doesn't leak. B-Mix 5 is just one of many white clay bodies that don't leak when fired to cone 6.

Jim

Hi, thank you for your reply, question though: Laguna states their Western BMix 5 has an absorption figure of 2.3%, plus or minus 1, their Northeastern BMix 5 is 2.75%, again plus or minus 1%. My clay tested out at 1.88% when fired in my kiln with my firing schedule. So, if your example of BMix not leaking even with Laguna's figures on absorption then why would my clay with a slightly lower figure weep? From reading Hamer's Dictionary of Materials and Techniques he states "although potters theoretically seek to get a pososity which is nil in their stoneware bodies, for practicality a very slight porosity is preferable. A porosity of 1% or 2% gives a much stronger body than one with no porosity at all" page 230 (original 1975 text). Lots of potters using a low porosity clay for mugs that don't leak, not to mention earthenware with it's high porosity. That being said I guess I'm wondering about the open or closed structure of the claybody itself, capillary action of the water through the clay. (No grog in the clay) I did use BMix for about 15 years but switched to white salmon as it fires much whiter and I was getting fed up picking bits of metal and wood out of the BMix from the last 1 ton batch I went through.

#5 Mark C.

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Posted 04 February 2013 - 05:14 PM




I am having an issue with one of the glazes I use not sealing the clay when fired to maturity. I use a ^6 claybody, Georgies White Salmon, firing to cone 6, tip of cone touching the shelf and the glaze that leads to weeping pots is Licorice from MC6Glazes. I have tried firing hotter (cone 7 tip nearly touching shelf) and the pots seep less but it's still an issue. To test for seeping I placed a glazed pot filled with water on newsprint and left it sit for 48 hours. Paper was wrinkled under the pot. Have tested several pots and they all weeped. The absorption was under 2 percent when I did a boil and weigh test of fired clay so I don't think it's an issue with the claybody, also, my other glazes don't have seepage problems. Anyone have any ideas how to fix this glaze? Thanks in advance for any help.



You are not having an issue with a glaze. You have a problem with a leaking clay body. You should not try to "seal" a pot with glaze. The test you did should have been done with an UNGLAZED pot. Almost always, glazing will not stop a clay from leaking and you shouldn't make any pot meant to hold a liquid unless an unglazed cylinder of it does not leak overnight on paper. (Even a slight dampness is leaking.) Sometimes it takes getting sued for a vase leaking on a grand piano for a potter to learn that they shouldn't sell leaking pots.

Switch to a ^6 clay that doesn't leak. B-Mix 5 is just one of many white clay bodies that don't leak when fired to cone 6.

Jim



Hi, thank you for your reply, question though: Laguna states their Western BMix 5 has an absorption figure of 2.3%, plus or minus 1, their Northeastern BMix 5 is 2.75%, again plus or minus 1%. My clay tested out at 1.88% when fired in my kiln with my firing schedule. So, if your example of BMix not leaking even with Laguna's figures on absorption then why would my clay with a slightly lower figure weep? From reading Hamer's Dictionary of Materials and Techniques he states "although potters theoretically seek to get a pososity which is nil in their stoneware bodies, for practicality a very slight porosity is preferable. A porosity of 1% or 2% gives a much stronger body than one with no porosity at all" page 230 (original 1975 text). Lots of potters using a low porosity clay for mugs that don't leak, not to mention earthenware with it's high porosity. That being said I guess I'm wondering about the open or closed structure of the claybody itself, capillary action of the water through the clay. (No grog in the clay) I did use BMix for about 15 years but switched to white salmon as it fires much whiter and I was getting fed up picking bits of metal and wood out of the BMix from the last 1 ton batch I went through.


The junk found in Laguna clay-this comes and goes with laguna west coast clays-Next to my wheel has a small jar full of it.
I will say that the cone 10 Geogies clays i tested years ago I was not happy with but it was not weeping issues-Sounds like you have done your testing and its not the body.
So maybe its that glaze and the fit-
usually its the body not matured but I assume this is a cone 6 clay???What's this clay listed to fire to?
I'm not a cone 6 guy so I will let the experts chine in .
Mark
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#6 OffCenter

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Posted 04 February 2013 - 05:27 PM





I am having an issue with one of the glazes I use not sealing the clay when fired to maturity. I use a ^6 claybody, Georgies White Salmon, firing to cone 6, tip of cone touching the shelf and the glaze that leads to weeping pots is Licorice from MC6Glazes. I have tried firing hotter (cone 7 tip nearly touching shelf) and the pots seep less but it's still an issue. To test for seeping I placed a glazed pot filled with water on newsprint and left it sit for 48 hours. Paper was wrinkled under the pot. Have tested several pots and they all weeped. The absorption was under 2 percent when I did a boil and weigh test of fired clay so I don't think it's an issue with the claybody, also, my other glazes don't have seepage problems. Anyone have any ideas how to fix this glaze? Thanks in advance for any help.


You are not having an issue with a glaze. You have a problem with a leaking clay body. You should not try to "seal" a pot with glaze. The test you did should have been done with an UNGLAZED pot. Almost always, glazing will not stop a clay from leaking and you shouldn't make any pot meant to hold a liquid unless an unglazed cylinder of it does not leak overnight on paper. (Even a slight dampness is leaking.) Sometimes it takes getting sued for a vase leaking on a grand piano for a potter to learn that they shouldn't sell leaking pots.

Switch to a ^6 clay that doesn't leak. B-Mix 5 is just one of many white clay bodies that don't leak when fired to cone 6.

Jim

Hi, thank you for your reply, question though: Laguna states their Western BMix 5 has an absorption figure of 2.3%, plus or minus 1, their Northeastern BMix 5 is 2.75%, again plus or minus 1%. My clay tested out at 1.88% when fired in my kiln with my firing schedule. So, if your example of BMix not leaking even with Laguna's figures on absorption then why would my clay with a slightly lower figure weep? From reading Hamer's Dictionary of Materials and Techniques he states "although potters theoretically seek to get a pososity which is nil in their stoneware bodies, for practicality a very slight porosity is preferable. A porosity of 1% or 2% gives a much stronger body than one with no porosity at all" page 230 (original 1975 text). Lots of potters using a low porosity clay for mugs that don't leak, not to mention earthenware with it's high porosity. That being said I guess I'm wondering about the open or closed structure of the claybody itself, capillary action of the water through the clay. (No grog in the clay) I did use BMix for about 15 years but switched to white salmon as it fires much whiter and I was getting fed up picking bits of metal and wood out of the BMix from the last 1 ton batch I went through.


The the junk found in Laguna clay-this comes and goes with laguna west coast clays-Next to my wheel has a small jar full of it.
I will say that the cone 10 Geogies clays i tested years ago I was not happy with but it was not weeping issues-Sounds like you have done your testing and its not the body.
So maybe its that glaze and the fit-
usually its the body not matured but I assume this is a cone 6 clay???What's this clay listed to fire to?
I'm not a cone 6 guy so I will let the experts chine in .
Mark


The glaze fit isn't an an issue. So, ignore the glaze and find a clay body that doesn't leak. I've never had any problems with B-mix 5 or B-mix 10 so those bad batches they were mixing up are hopefully long gone. I don't pay much attention to the published stats for a clay body because I test them myself. All I can tell you is that the B-mix 5 i've used the past several years does not leak. For white I use Southern Ice cone 10-11 and Frost cone 6. They don't leak either.

Jim
E pur si muove.

"But it does move," said Galileo under his breath.

#7 Ben

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Posted 06 February 2013 - 08:48 AM

"""The glaze fit isn't an an issue. .<br style="color: rgb(28, 40, 55); font-family: arial, verdana, tahoma, sans-serif; font-size: 13px; line-height: 19px; background-color: rgb(250, 251, 252);"><br style="color: rgb(28, 40, 55); font-family: arial, verdana, tahoma, sans-serif; font-size: 13px; line-height: 19px; background-color: rgb(250, 251, 252);">Jim """


It could be. I've had glaze fit mismatches that seriously weakened and even broke pots. It is possible that the glaze is cracking the pots causing leakage. That is not to say that the glaze is leaking but it may be causing the pot to break/leak.
Making a bare, unglazed test pot will tell you if the clay is leaking. To test the clays COE you can use a coefficient of expansion series of glazes each with an increasing coe but starting well below a useful coe and going well above. It could be that the glaze and clay are so mismatched in COE that they are weakening each other. MC6G outlines this method.

#8 Diane Puckett

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Posted 08 February 2013 - 04:45 PM

Per Fraser in his book on electric kilns, the bottom of a pot sitting on a kiln shelf does not get as hot, because it is insulated by the shelf. I wonder if this could affect vitrification of pot bottoms, particularly those without feet.
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#9 Celia UK

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Posted 15 November 2013 - 02:47 PM

Can my white earthenware 1060-1120 oC be used to make coffee mugs and other functional pieces? Should I fire to the upper end of the range? I've read that earthenware doesn't really vitrify, so in my head it won't be waterproof. Is this where the glaze comes in? What about the bottom? Should I glaze the bottoms and fire on stilts?

Any advice most welcome.

#10 Peter J.

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Posted 19 November 2013 - 09:31 PM

I am having an issue with one of the glazes I use not sealing the clay when fired to maturity. I use a ^6 claybody, Georgies White Salmon, firing to cone 6, tip of cone touching the shelf and the glaze that leads to weeping pots is Licorice from MC6Glazes. I have tried firing hotter (cone 7 tip nearly touching shelf) and the pots seep less but it's still an issue. To test for seeping I placed a glazed pot filled with water on newsprint and left it sit for 48 hours. Paper was wrinkled under the pot. Have tested several pots and they all weeped. The absorption was under 2 percent when I did a boil and weigh test of fired clay so I don't think it's an issue with the claybody, also, my other glazes don't have seepage problems. Anyone have any ideas how to fix this glaze? Thanks in advance for any help.

 

I'll chime in to say that I've been using their White Salmon for a few years now and have made a number of vases and mugs using the M^6  Licorice recipe as a liner and have never had problems.  I did come across a similar problem with Plainsman F-95 though.  A beautiful raw finish at ^6 but leaks like mad.  I just use it for decorative pieces with little if any glaze..

 

just my 2cents....



#11 Chris Throws Pots

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Posted 20 November 2013 - 10:16 AM

The junk found in Laguna clay-this comes and goes with laguna west coast clays-Next to my wheel has a small jar full of it.

 

Laguna Ohio as well. Recently I found a rusty nail, a chunk of zip tie, and several very large splinters of wood across a few bags of #90. I know it's off topic from the thread, but it's nice (and sad at the same time) to hear I'm not alone.


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#12 Babs

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Posted 20 November 2013 - 04:25 PM

Can my white earthenware 1060-1120 oC be used to make coffee mugs and other functional pieces? Should I fire to the upper end of the range? I've read that earthenware doesn't really vitrify, so in my head it won't be waterproof. Is this where the glaze comes in? What about the bottom? Should I glaze the bottoms and fire on stilts?

Any advice most welcome.

Go to your supplier and ask. It really depends on the clay body. You can make mugs in your firing range. I put feet on my mugs and glaze everything except for a ring at the bottom of the foot. Also have stilted mugs, OK for a smalll number but tedious for a lot. Some people even put a waterproof seal on the foot after  glaze firing. Non of the above may be necessary with an appropriate body. Your supplier should give you that info, ofr Google it.



#13 jrgpots

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Posted 20 November 2013 - 11:00 PM

I noticed that Offcener commented on this post in Feb before his blow up. I miss him

#14 Biglou13

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Posted 21 November 2013 - 01:02 AM

Me too!

I started reading this thread and was excited to see him back...... Only to realize it is an old post.
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#15 oldlady

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Posted 21 November 2013 - 09:07 AM

i think he may be occasionally  lurking among the anonymous users.  

 

if you are, jim, i tried some frost.  got it as thin as three business cards, stacked.  made a candle surround and left it white (Not yet fired) and a second one with a row of joined paper dolls left white and a blue slip background.  delicate stuff, isn't it?

 

i learned that frost is very fragile and that i need a wide sponge roller to apply slip.

 

l also learned (again!) to load the kiln with two hands. :o


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#16 Chilly

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Posted 14 February 2014 - 03:46 PM

Can my white earthenware 1060-1120 oC be used to make coffee mugs and other functional pieces? Should I fire to the upper end of the range? I've read that earthenware doesn't really vitrify, so in my head it won't be waterproof. Is this where the glaze comes in? What about the bottom? Should I glaze the bottoms and fire on stilts?

Any advice most welcome.

 

I've made functional stuff with earthenware, fully glazed and stilted, but find it's not as durable as stoneware.  So for functional stuff I now always fire to cone 6.  As an aside, I made a pot to sit on the fireplace to hold the kindling, it's earthenware, to match some vases I made.  It gets picked up every other day and taken out to be re-filled.  Picked it up one day, and it had cracked into many pieces.  The other half denies dropping it,so I suppose it must be glaze mismatch.  Now going to have to make another, but this time it will be stoneware.  Shame the glaze won't match the vases.  Oh no, then I'll have to make new vases.............


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