I was recently looking at celadon ware and it's gorgeous! Just wondering about the crackling effect. Won't tea absorb into the teacups through these cracks? Anyone had an experience with these, drinking tea long-term?
Thanks
Sep 26th, '09, 23:28
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Re: Celadon cups
You may have seen other types of crackle glazes before - the cracks are underneath the surface and not exposed, so unless it gets cracked afterwards there's really nothing to worry about.
Sep 27th, '09, 01:09
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Re: Celadon cups
It depends. Are you talking about celadon of following kinds?
I have a cup similar to this one. The crackling is under the surface and tea stain won't get in.
Another one of mine similar to this, the crackling is on the surface and the cup will be stained, so the cup is fed with tea water, in a way comparable to yixing fed with tea water.
I have a cup similar to this one. The crackling is under the surface and tea stain won't get in.
Another one of mine similar to this, the crackling is on the surface and the cup will be stained, so the cup is fed with tea water, in a way comparable to yixing fed with tea water.
Sep 27th, '09, 10:16
Posts: 1796
Joined: Sep 15th, '09, 16:11
Location: Wilton, New Hampshire USA
Re: Celadon cups
The technical term for that is "crazing". It is caused when, during the cooling cycle of the kiln's glaze firing, the layer of glass on the outside of the pot shrinks more than the clay body under it. Glass is very weak in tension, so it fractures. From an "industrial" standpoint... it is a defect.
This is typically cureable if that is desired. The simple addition of some SiO2 (silica) into the glaze batch will usually change the expansion/shrinkage factor of the glaze so that it will match that of the body.
From the studio potter's viewpoint crazing can either be a defect to be corrected...... or a desired outcome. Or even just something that is "there" and is not deliberately considered or looked as as long as the visual result is pleasing.
As has already been described above, some sophisticated and deliberate "crackle" can also be done so that the crazing is visually evident in the glass but the glaze surface has been sealed of the cracks. These represent some very good control of the process.
You might tend to call it "crackle" when it is deliberate, and "crazing" when it is not. Other than the healed over variety, which is always a deliberate act, one person's "crackle" might be another person's "crazing".
Part of the "patina" for some functional works is that the crazing/ crackle does slowly get stained in. So the piece "matures" only in use. And is in a state of constant change...... which can be a nice concept. Although not from crazing, another type of ware that "changes" in use is Bizenyaki. Bizenyaki is said to require 50-60 years of functional use to develop its full patina.
best,
............john
This is typically cureable if that is desired. The simple addition of some SiO2 (silica) into the glaze batch will usually change the expansion/shrinkage factor of the glaze so that it will match that of the body.
From the studio potter's viewpoint crazing can either be a defect to be corrected...... or a desired outcome. Or even just something that is "there" and is not deliberately considered or looked as as long as the visual result is pleasing.
As has already been described above, some sophisticated and deliberate "crackle" can also be done so that the crazing is visually evident in the glass but the glaze surface has been sealed of the cracks. These represent some very good control of the process.
You might tend to call it "crackle" when it is deliberate, and "crazing" when it is not. Other than the healed over variety, which is always a deliberate act, one person's "crackle" might be another person's "crazing".
Part of the "patina" for some functional works is that the crazing/ crackle does slowly get stained in. So the piece "matures" only in use. And is in a state of constant change...... which can be a nice concept. Although not from crazing, another type of ware that "changes" in use is Bizenyaki. Bizenyaki is said to require 50-60 years of functional use to develop its full patina.
best,
............john
Re: Celadon cups
John,
You seem quite knowledgeable about pottery materials. I own some lovely bizen guinomi and am relectant to wash them with soap. Am I just being too protective or do wood fired yohen type wares still absorb flavors and smells even though they are high fired? I'm even wondering if some fully glazed wares are not still absorbing something into them.
You seem quite knowledgeable about pottery materials. I own some lovely bizen guinomi and am relectant to wash them with soap. Am I just being too protective or do wood fired yohen type wares still absorb flavors and smells even though they are high fired? I'm even wondering if some fully glazed wares are not still absorbing something into them.
Sep 30th, '09, 07:42
Posts: 1796
Joined: Sep 15th, '09, 16:11
Location: Wilton, New Hampshire USA
Re: Celadon cups
Teadoff,
Hi. Thanks for the kind words. We could write a book on this subject.
Most "stoneware" (high fire) clay bodies of all types actually are VERY slightly porous. They might be in the absorbtion range of about 1%. Which means that if you soaked the piece in water until it was as saturated as it can possibly get, it would absorb about 1% of its weight in water. Some stonewares are slightly higher than this, some are lower.
When a stoneware clay body gets down to 0% absorbtion, it is very close to being "overfired". That makes control of the firing very tricky if the body is taken that far. A slight increase in the temperature/firing time relationship after that, and a number of defects can start happening. So being VERY slightly porous gives the potter a slight "margin for error" on a number of potential problems.
As an experiment, take a Bizen guinomi (or any yakishime one) you have that you USE for sake that is currently sitting on a shelf or in a box. Take a good deep sniff with your nose stuffed into it. Bet you'll still smell the sake even though you rinsed it out with water very well after you used it (even if you used soap too).
Bizenyaki's surface CAN be slightly porous......not always though because of the natural variations in the woodfiring process. Part of the great effects that woodfire gets are created by a certain un-evenness of the temperature distribution and atmosphere of the kiln. Those variations around a piece can even result in one area of a piece being slightly lower fired than another part of it. That lower fired area will have a higher porosity than the higer fired area. The higher fired areas might even have a 0% absorbtion. Then you add in factors that affect absorbtion like shizenyu (natural ash glaze deposits) on some parts of the piece. Gets complicated.
When in Japan, I have been told by a number of Bizen potters that the pieces require the aging of being in use to develop the final look of the surface. The numbers given are always between 50 and 60 years. It is my experience with the pieces that I have of this type that they DO change with the gradual absorbtion of food oils and the gradual polishing effects of hand washing after use. I have a number of food service type items that we regularly use and wash along with all of our dishes. They are slowly getting more and more beautiful.
One technique that Bizen potters sometimes use to "hasten" the aging process is to soak the pieces in a mixture of sake and oil. I've never been able to get out of one of them exactly what kind of oil. (If someone here knows.... please share it.) I am guessing some sort of vegetable oil. I have tried this and use it occasionally. It does improve the patina rapidly.
I would never use this soaking technique on a chawan or a guinomi though. It is more appropriate to hanaire and other types of items. The possibility of affecting the taste or bouquet of the contents for sake or tea would be too great, I think. If a guinomi is to "age", I want it to be from sake alone. And a chawan from tea alone.
I do quite a bit of work with various forms of youhen in my work. Currently one or two chambers of my 5 chamber noborigama every firing are burried in charcoal at the end of the firing process similar to one of the Bizen processes (one they don't share information about too readily ).
Glazed surfaces are another situation with this issue, and we could write another book here. If the glaze is intact (no crazing or pinholes), then for all intents and purposes the surface is basically a barrier to water (and other stuff). If however there is crazing, then liquid can (slowly) get thru the glaze and reach the clay body underneath. Then the porosity of the clay body is an issue to any potential absorbtion. Plus material can get trapped in the tiny crazing lines.
Some types of glazes which have more "unique" surfaces can themselves be a bit porous. If so, then the underlying body absorbtion can also be a factor in this.
So you are correct that these types of pieces CAN possibly pick up odors and flavors from previous use and possible subtle "contamination" if mixed with the general dishes. The more discerning your nose and pallate.... the more this can be an issue. It is part of why some particular clays and glazes affect the flavor of the tea more than others. And why certain aging processes and washing processes are necessary for certain types of teaware.
I tell my students that the correct answer to just about ANY question about technical ceramic process is, "It depends". There are SO many variables involved in the ceramic process that a single answer is almost never one that will be correct in every case.
Assessing this technical stuff correctly can be like a doctor gathering information for a diagnosis; is that headache a "headache",...... or a brain tumor? To be sure, you need lots of tests and information.
Anyway.... hope that helps. I have to go now.... getting ready for heading off to teach at the college today.
best,
............john
Hi. Thanks for the kind words. We could write a book on this subject.
Most "stoneware" (high fire) clay bodies of all types actually are VERY slightly porous. They might be in the absorbtion range of about 1%. Which means that if you soaked the piece in water until it was as saturated as it can possibly get, it would absorb about 1% of its weight in water. Some stonewares are slightly higher than this, some are lower.
When a stoneware clay body gets down to 0% absorbtion, it is very close to being "overfired". That makes control of the firing very tricky if the body is taken that far. A slight increase in the temperature/firing time relationship after that, and a number of defects can start happening. So being VERY slightly porous gives the potter a slight "margin for error" on a number of potential problems.
As an experiment, take a Bizen guinomi (or any yakishime one) you have that you USE for sake that is currently sitting on a shelf or in a box. Take a good deep sniff with your nose stuffed into it. Bet you'll still smell the sake even though you rinsed it out with water very well after you used it (even if you used soap too).
Bizenyaki's surface CAN be slightly porous......not always though because of the natural variations in the woodfiring process. Part of the great effects that woodfire gets are created by a certain un-evenness of the temperature distribution and atmosphere of the kiln. Those variations around a piece can even result in one area of a piece being slightly lower fired than another part of it. That lower fired area will have a higher porosity than the higer fired area. The higher fired areas might even have a 0% absorbtion. Then you add in factors that affect absorbtion like shizenyu (natural ash glaze deposits) on some parts of the piece. Gets complicated.
When in Japan, I have been told by a number of Bizen potters that the pieces require the aging of being in use to develop the final look of the surface. The numbers given are always between 50 and 60 years. It is my experience with the pieces that I have of this type that they DO change with the gradual absorbtion of food oils and the gradual polishing effects of hand washing after use. I have a number of food service type items that we regularly use and wash along with all of our dishes. They are slowly getting more and more beautiful.
One technique that Bizen potters sometimes use to "hasten" the aging process is to soak the pieces in a mixture of sake and oil. I've never been able to get out of one of them exactly what kind of oil. (If someone here knows.... please share it.) I am guessing some sort of vegetable oil. I have tried this and use it occasionally. It does improve the patina rapidly.
I would never use this soaking technique on a chawan or a guinomi though. It is more appropriate to hanaire and other types of items. The possibility of affecting the taste or bouquet of the contents for sake or tea would be too great, I think. If a guinomi is to "age", I want it to be from sake alone. And a chawan from tea alone.
I do quite a bit of work with various forms of youhen in my work. Currently one or two chambers of my 5 chamber noborigama every firing are burried in charcoal at the end of the firing process similar to one of the Bizen processes (one they don't share information about too readily
).Glazed surfaces are another situation with this issue, and we could write another book here. If the glaze is intact (no crazing or pinholes), then for all intents and purposes the surface is basically a barrier to water (and other stuff). If however there is crazing, then liquid can (slowly) get thru the glaze and reach the clay body underneath. Then the porosity of the clay body is an issue to any potential absorbtion. Plus material can get trapped in the tiny crazing lines.
Some types of glazes which have more "unique" surfaces can themselves be a bit porous. If so, then the underlying body absorbtion can also be a factor in this.
So you are correct that these types of pieces CAN possibly pick up odors and flavors from previous use and possible subtle "contamination" if mixed with the general dishes. The more discerning your nose and pallate.... the more this can be an issue. It is part of why some particular clays and glazes affect the flavor of the tea more than others. And why certain aging processes and washing processes are necessary for certain types of teaware.
I tell my students that the correct answer to just about ANY question about technical ceramic process is, "It depends". There are SO many variables involved in the ceramic process that a single answer is almost never one that will be correct in every case.
Assessing this technical stuff correctly can be like a doctor gathering information for a diagnosis; is that headache a "headache",...... or a brain tumor? To be sure, you need lots of tests and information.
Anyway.... hope that helps. I have to go now.... getting ready for heading off to teach at the college today.
best,
............john
Re: Celadon cups
John,
So how do you clean your bizen ware? Or, Raku?
I bought an old raku chawan on ebay recently that has a horrible mildew smell. I can't even keep it in the kitchen as it will smell up the whole room. I am currently soaking it in Baking Soda put into boiling hot water. Any solutions to this? Thanks.
So how do you clean your bizen ware? Or, Raku?
I bought an old raku chawan on ebay recently that has a horrible mildew smell. I can't even keep it in the kitchen as it will smell up the whole room. I am currently soaking it in Baking Soda put into boiling hot water. Any solutions to this? Thanks.
Re: Celadon cups
John: the oil used is very likely to be 'hair of the dog'.
Sake is fermented rice alcohol.
Rice bran oil is your best bet for the 'secret' ingredient that is highly compatible with the flavor of sake and may even enhance it.
Sake is fermented rice alcohol.
Rice bran oil is your best bet for the 'secret' ingredient that is highly compatible with the flavor of sake and may even enhance it.
Re: Celadon cups
I miss sake.
The have some really excellent ones at Uwajimaya in Seattle's International District.
I used to be able to walk there *sigh*
The have some really excellent ones at Uwajimaya in Seattle's International District.
I used to be able to walk there *sigh*
Oct 2nd, '09, 15:33
Posts: 1796
Joined: Sep 15th, '09, 16:11
Location: Wilton, New Hampshire USA
Re: Celadon cups
Tead Off,
For the general food tableware I have of the Bizenyaki type they get washed with a mild diswashing soap and rinsed really well and then dried off immediately.
For guinomi and chawan, they typically get rinsed out with really hot water and rubbed with a clean scotchbrite type scrubbie pad. They only see a tiny bit of dish soap if there is some GOOD reason that they need more aggressive cleaning (like forgetting to wash a guinomi and the sake reside has dried in it overnight).
As to the raku you mention....are we talking the typical American type "raku" or Japanese raku ware? They are QUITE different animals as to how they are made and also my recommendations as pertaining to use.
The "stink" you are mentioning there is likely not good from a food hygene / toxicology persepctive. The source could be many things...... from some "spray on age smell" used by some bogus "antique" dealers to take new items and make them seem old so they can rip you off......... to the growth of mold / mildew in the porous clay body from prolonged dampness.
Whether it is American type raku or Japanese raku, I'd suggest that the best way to deal with this is to put the bowl in an unheated home oven. Set the oven to 400F, and then let it heat up with the bowl in there. Let the bowl "cook" at that 400F temperature for a couple of hours. Then turn off the oven and leave the bowl in it until it all cools to room temperature.
You likely will get some smells in the kitchen in the early stages. Open a window .
That treatment should "kill" any mold/mildew type things in the pores without affecting the bowl itself. Don't get it as hot as 450F...... that CAN start to change the bowl, particularly if it is typical American raku.
If the source of the smell is some sort of chemicals absorbed into the piece....... that above solution will likely not help; "crap" will likely still be in the bowl's pores even if the smell is killed. Do you know the full "history" of the piece? Or did you get it with the smell already there?
best,
.............john
For the general food tableware I have of the Bizenyaki type they get washed with a mild diswashing soap and rinsed really well and then dried off immediately.
For guinomi and chawan, they typically get rinsed out with really hot water and rubbed with a clean scotchbrite type scrubbie pad. They only see a tiny bit of dish soap if there is some GOOD reason that they need more aggressive cleaning (like forgetting to wash a guinomi and the sake reside has dried in it overnight).
As to the raku you mention....are we talking the typical American type "raku" or Japanese raku ware? They are QUITE different animals as to how they are made and also my recommendations as pertaining to use.
The "stink" you are mentioning there is likely not good from a food hygene / toxicology persepctive. The source could be many things...... from some "spray on age smell" used by some bogus "antique" dealers to take new items and make them seem old so they can rip you off......... to the growth of mold / mildew in the porous clay body from prolonged dampness.
Whether it is American type raku or Japanese raku, I'd suggest that the best way to deal with this is to put the bowl in an unheated home oven. Set the oven to 400F, and then let it heat up with the bowl in there. Let the bowl "cook" at that 400F temperature for a couple of hours. Then turn off the oven and leave the bowl in it until it all cools to room temperature.
You likely will get some smells in the kitchen in the early stages. Open a window
.That treatment should "kill" any mold/mildew type things in the pores without affecting the bowl itself. Don't get it as hot as 450F...... that CAN start to change the bowl, particularly if it is typical American raku.
If the source of the smell is some sort of chemicals absorbed into the piece....... that above solution will likely not help; "crap" will likely still be in the bowl's pores even if the smell is killed. Do you know the full "history" of the piece? Or did you get it with the smell already there?
best,
.............john
Oct 2nd, '09, 15:35
Posts: 1796
Joined: Sep 15th, '09, 16:11
Location: Wilton, New Hampshire USA
Re: Celadon cups
Intuit,Intuit wrote:John: the oil used is very likely to be 'hair of the dog'.
Sake is fermented rice alcohol.
Rice bran oil is your best bet for the 'secret' ingredient that is highly compatible with the flavor of sake and may even enhance it.
Aha..... thanks. Didn't THINK of that source. Do you think rice bran oil is available in the USA.....or am I going to have to pack some in my checked luggage the next time I am headed back from Japan?
best,
...........john
Oct 2nd, '09, 15:41
Posts: 1796
Joined: Sep 15th, '09, 16:11
Location: Wilton, New Hampshire USA
Re: Celadon cups
Depravitea,depravitea wrote:I miss sake.
The have some really excellent ones at Uwajimaya in Seattle's International District.
I used to be able to walk there *sigh*
The more time I spend in Japan ....the worse it is coming home to the inadequately available Japanese products here of all sorts. I have a wine society place here in southern NH that has some better sakes than the cheapo drainopener Geikeikan crap you find everywehere..... but they are still VERY limited.
I discovered a new one (for me) this summer over there...... Ho Hai produced in the Tohoku region (Miyorashaizo in Hirosaki, I think). Wonderful. Wish I could get it here. Shoga nai.
best,
..........john
Re: Celadon cups
John, I would try NOW Foods for high quality rice bran oil. It's got the low smoke at high temp qualities of peanut oil, but half the C-20 (arachadonic acid) content. If you buy it in bulk, you can also use it for cooking for which it's excellent (on par with grapeseed oil, which would be another candidate if you wish a more colorless/flavorless food grade oil).
Comparative fatty acid profile:
http://www.ricebranoil.info/why/index.html
Comparative fatty acid profile:
http://www.ricebranoil.info/why/index.html
Oct 2nd, '09, 18:17
Posts: 1796
Joined: Sep 15th, '09, 16:11
Location: Wilton, New Hampshire USA
Re: Celadon cups
Intuit,
THANKS for that info. Likely will be off to buy some rice bran oil to test soon. Not to mention making some tempura .
best,
..........john
THANKS for that info. Likely will be off to buy some rice bran oil to test soon. Not to mention making some tempura
.best,
..........john
Re: Celadon cups
John,
The stinky raku bowl is Japanese. I have been soaking it in a baking soda paste for the last 2 days. It still stinks. This must have been in some dank, dark room for a long time. There was so much stink that I would be afraid of putting it in my oven. It is hot here in Thailand. This will add to the overall smell. Thanks for the tip. I'll talk with my wife and see what she wants to do with it. Maybe somebody wants to trade for a stinky raku chawan?!
The stinky raku bowl is Japanese. I have been soaking it in a baking soda paste for the last 2 days. It still stinks. This must have been in some dank, dark room for a long time. There was so much stink that I would be afraid of putting it in my oven. It is hot here in Thailand. This will add to the overall smell. Thanks for the tip. I'll talk with my wife and see what she wants to do with it. Maybe somebody wants to trade for a stinky raku chawan?!