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Wood Firing for Shino : Reduction phases


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#1 timbo_heff

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Posted 24 May 2013 - 10:19 AM

Greetings Kiln Masters !
I am about to fire a small (70 cu ft setting) anagama inspired tube kiln.
There seem to be as many different opinions as there are people but I thought I might as well pick the brains of you all who have lots more experience than I do.

Some details:
Shooting for cone 11/12 front 9/10 back
Mostly sheffield clays : Z, Wood Light, 42, T1, T3, 95400 white stoneware, some bMix. Some greenware so long campfire preheat.
4 day firing is the goal; with about 4 cords of mixed hardwoods.
Some unglazed in the front, shino, Mark's tenmoku and other miscellaneous glazes throughout.
Shino is "Gustin shino" : (not carbon trap.)

With the goal of maximizing the beauty of the shino:
Question 1) At what cone to do body reduction and for how long ?
Question 2) At what cone do you start glaze reduction and for how long?
Question 3) How long do you oxidize at the end?
Question 4) Do you down fire? and if so what 's your firing schedule for that?

Thanks for sharing your knowledge and experience. This crazy sport of wood firing seems more like alchemy than science so all opinions are welcome !
best
-tim.


#2 JBaymore

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Posted 24 May 2013 - 12:56 PM

Tim,

So what is the goal for the shinos? Carbon trap? One just fire color? Carbon trap to the max (black shino).... or more subtle mixtures of color and blackness?

For heavy carbon trap.... you almost can't reduce too low. (Don't take that literallyPosted Image. ) For average carbon trapping I use about cone 010 as the starting point. With MY shino formulation if I get to about cone 05..... carbon trapping is not really possible anymore..... outer glaze surface is sealed over with highly soda fluxed glass.

Watch tenmokus in long duration firings.... they can run.

In my noborigama I have the luxury of firing different chambers in different atmospheres and to different end point cones... so I use all sorts of firing cycles. Some Japanese style shino I do has very, very light reduction at all... like much Japanese shino ware, the glaze is quite white with light red firecolor on the thin spots.

I don't think of "body reduction" and "glaze reduction".... it is all one continuum. In a wood kiln you are cycling from pretty strong reduction to pretty strong oxidiation on most every stoke anyway once you are at a certain temperature. I look at HOW HEAVY it swings to reduction on the stokes rather than holding it in a steady state of reduction constantly. The length of those reduscion periods also varies relative to the oxidation periods as the stoking rate.volume goes up on a single stoke.

As to downfiring.... on my last one or two chambers I often use the Bizen-style youhen charcoal technique.... and that REALLY retards the cooling and holds it in HEAVY reduction until the wares are not really reactive anymore.

best,

.............john
John Baymore
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Professor of Ceramics; New Hampshire Insitute of Art

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#3 timbo_heff

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Posted 24 May 2013 - 03:57 PM

Thanks John for sharing your insight !

"So what is the goal for the shinos? Carbon trap? One just fire color? Carbon trap to the max (black shino).... or more subtle mixtures of color and blackness?"

Not doing Davis Carbon Trap (I actually don't care for that look very much) The Gustin Shino I use is pretty white on light clay and quite rich over the 42 especially if thin: Really want to maximize the ruddy flashing and ash effects. But I don't really want the clean white look: funky as possible... so I guess "the subtle mixtures of color and blackness"

I thought you want to oxide on the down fire to brighten up the colors? Wrong?

#4 Biglou13

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Posted 24 May 2013 - 06:37 PM

Thanks John for sharing your insight !

"So what is the goal for the shinos? Carbon trap? One just fire color? Carbon trap to the max (black shino).... or more subtle mixtures of color and blackness?"

Not doing Davis Carbon Trap (I actually don't care for that look very much) The Gustin Shino I use is pretty white on light clay and quite rich over the 42 especially if thin: Really want to maximize the ruddy flashing and ash effects. But I don't really want the clean white look: funky as possible... so I guess "the subtle mixtures of color and blackness"

I thought you want to oxide on the down fire to brighten up the colors? Wrong?


Shinos have many different faces. So difficult to answer? Carbon trapping is but one of many faces of shino. While I've never wood fired I have spent some time researching . The re are many artist that specialize in shino. Judith duff, has much information on her website, regarding her kiln and firing technique. I really love the variety one can get from, one shino glaze in different parts of kiln. From whites,to reds light reds , purples, greys, spotting, Mixes of...... .same shino with different application techniques, produce differnt looks. How long a glaze sits on piece can affect outcome. Then to complicate further how clay bodies will react with , shino, fire, placement In kiln, firing technique. Hope fully you made notes of clay and glazes. Also note what part of kiln pieces were fired. Lots of photos and or videos may help with the note taking on kiln opening. If you haven't loaded yet maybe you could saggar fire a few pieces.. Unfortunately there are way to many variable in play. To answer your questions. While the glaze says carbon trap ........ Doesn't mean you get carbon trapping, Again much depends of firing and what the kiln gods feeling like giving you. It's the variety of results and beauty of this glaze that draws me to it.
While probably not a true shino in the sense I've been working on a. Cone 6 ox shino with very pleasant results.

sensei. John B. (Yoda). has probably the most experienced in japanese pottery and chajin, that is involved with this site. (If you didn't already know). So if your questions were answerable you have the right source.


Timbo.

I like the way you think.
Please take photos, post with progress.
Caution big brother is watching.
The beige is blinding!!!!!!
The middle of the road is boring

The true sign of intelligence is not knowledge but imagination.
-Albert Einstein

#5 OffCenter

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Posted 24 May 2013 - 07:02 PM


Thanks John for sharing your insight !

"So what is the goal for the shinos? Carbon trap? One just fire color? Carbon trap to the max (black shino).... or more subtle mixtures of color and blackness?"

Not doing Davis Carbon Trap (I actually don't care for that look very much) The Gustin Shino I use is pretty white on light clay and quite rich over the 42 especially if thin: Really want to maximize the ruddy flashing and ash effects. But I don't really want the clean white look: funky as possible... so I guess "the subtle mixtures of color and blackness"

I thought you want to oxide on the down fire to brighten up the colors? Wrong?


Shinos have many different faces. So difficult to answer? Carbon trapping is but one of many faces of shino. While I've never wood fired I have spent some time researching . The re are many artist that specialize in shino. Judith duff, has much information on her website, regarding her kiln and firing technique. I really love the variety one can get from, one shino glaze in different parts of kiln. From whites,to reds light reds , purples, greys, spotting, Mixes of...... .same shino with different application techniques, produce differnt looks. How long a glaze sits on piece can affect outcome. Then to complicate further how clay bodies will react with , shino, fire, placement In kiln, firing technique. Hope fully you made notes of clay and glazes. Also note what part of kiln pieces were fired. Lots of photos and or videos may help with the note taking on kiln opening. If you haven't loaded yet maybe you could saggar fire a few pieces.. Unfortunately there are way to many variable in play. To answer your questions. While the glaze says carbon trap ........ Doesn't mean you get carbon trapping, Again much depends of firing and what the kiln gods feeling like giving you. It's the variety of results and beauty of this glaze that draws me to it.
While probably not a true shino in the sense I've been working on a. Cone 6 ox shino with very pleasant results.

sensei. John B. (Yoda). has probably the most experienced in japanese pottery and chajin, that is involved with this site. (If you didn't already know). So if your questions were answerable you have the right source.


Timbo.

I like the way you think.
Please take photos, post with progress.


Yoda! Yes. Yoda is a little better looking but still perfect!

Jim
E pur si muove.

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

#6 Kohaku

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Posted 24 May 2013 - 07:40 PM

Oh dear heavens... I want access to a wood kiln so bad! I did a little shino firing at a University class, and loved it to death. About the only thing so far that gets me as wobbly knee'd as Raku.

Yes, Stephen Hill, I like your oxidation surfaces just fine... but talk all you want, it's just not the same thing...
Not all who wander are lost

#7 OffCenter

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Posted 24 May 2013 - 10:00 PM

Oh dear heavens... I want access to a wood kiln so bad! I did a little shino firing at a University class, and loved it to death. About the only thing so far that gets me as wobbly knee'd as Raku.

Yes, Stephen Hill, I like your oxidation surfaces just fine... but talk all you want, it's just not the same thing...


No, it's not the same thing but just as good.

Jim
E pur si muove.

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

#8 JBaymore

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Posted 25 May 2013 - 10:44 AM

Not doing Davis Carbon Trap (I actually don't care for that look very much)


Yoda! Yes. Yoda is a little better looking but still perfect!


Ahhh, carbon trap is not your destiny I can see, eh. Soluble soda sources in the glaze recipe diminish you should. Early strong reduction in the kiln want you should not. To the Dark Side those paths lead.

To the easy path of Soda Ash do not give in. Soda ash leads to solubility. Solubility leads to water evaporation ionic migration. Water evaporation ionic migration leads to early melting glaze surfaces. Early melting glaze surfaces leads to gas impermeability.

May the Feldspar be with you......always.

best,

..............the Yoda of SodaPosted Image
John Baymore
Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

http://www.JohnBaymore.com

#9 timbo_heff

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Posted 25 May 2013 - 02:58 PM

Even with the protection of the Yoda of Soda, the kiln god(s) are giving me the big raspberry right now; days on end of dumping pouring rain and high winds.
So much for my bonus wood seasoning and prep day :(

#10 Biglou13

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Posted 04 June 2013 - 08:06 AM

Any results?
Caution big brother is watching.
The beige is blinding!!!!!!
The middle of the road is boring

The true sign of intelligence is not knowledge but imagination.
-Albert Einstein

#11 TJR

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Posted 04 June 2013 - 09:25 AM

Even with the protection of the Yoda of Soda, the kiln god(s) are giving me the big raspberry right now; days on end of dumping pouring rain and high winds.
So much for my bonus wood seasoning and prep day Posted Image


Up here in Canada we cover our wood with plastic. It's a great invention. It repels rain. Try some you should.
TJR.

#12 timbo_heff

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Posted 15 June 2013 - 06:20 AM

Attached File  wf13-2.jpg   814.6KB   53 downloadsSuper fantastic fire! 400 pots, 95% good. Great diversity... 14 potters in kiln. About 4 days, about 4 cords. Reduction phases around 08 and again at top temp. ^10/12 front stack, ^9/10 back.
Here are a few of mine: some unglazed, some shino. Attached File  wf13-1.jpg   771.3KB   58 downloads

#13 OffCenter

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Posted 15 June 2013 - 07:48 AM

Attached File  wf13-2.jpg   814.6KB   53 downloadsSuper fantastic fire! 400 pots, 95% good. Great diversity... 14 potters in kiln. About 4 days, about 4 cords. Reduction phases around 08 and again at top temp. ^10/12 front stack, ^9/10 back.
Here are a few of mine: some unglazed, some shino. Attached File  wf13-1.jpg   771.3KB   58 downloads


Looks like a good firing. Good ash.

Jim
E pur si muove.

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

#14 Biglou13

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Posted 15 June 2013 - 08:04 AM

Attached File  wf13-2.jpg   814.6KB   53 downloadsSuper fantastic fire! 400 pots, 95% good. Great diversity... 14 potters in kiln. About 4 days, about 4 cords. Reduction phases around 08 and again at top temp. ^10/12 front stack, ^9/10 back.
Here are a few of mine: some unglazed, some shino. Attached File  wf13-1.jpg   771.3KB   58 downloads


NICE!!!!!

More pics please?

Any more info on firing?

Thanks
Caution big brother is watching.
The beige is blinding!!!!!!
The middle of the road is boring

The true sign of intelligence is not knowledge but imagination.
-Albert Einstein

#15 timbo_heff

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Posted 17 June 2013 - 08:34 AM

Here's something strange that happened: a couple of big thick (1") shelves seem to have fluxed and melted. They bubbled and foamed and dripped onto pots below. The "glaze" they made luckily looks pretty cool: blue and black, super glassy and deep. The one pictured was right up front but it happened further back as well.
Anyone ever have this happen?
Attached File  shelves.jpg   1.03MB   31 downloads

#16 Biglou13

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Posted 17 June 2013 - 11:34 AM

Here's something strange that happened: a couple of big thick (1") shelves seem to have fluxed and melted. They bubbled and foamed and dripped onto pots below. The "glaze" they made luckily looks pretty cool: blue and black, super glassy and deep. The one pictured was right up front but it happened further back as well.
Anyone ever have this happen?
Attached File  shelves.jpg   1.03MB   31 downloads


how much ash/glaze deposit was on shelf before? did you see shelves before firing?
how do the top of shelves look?
are shelves used one side up only?
have shelves been used in soda/salt firings?
was it all shelves or just a few?

i'm gonna take a wild guess...... ash deposit/glaze, with old deposit from previous firings.

very interesting,cant wait to here what the wizards of wood firing have to say.

any more info on firing, eg .... cooling reduction, oxidation run a peak.....any chance there is firing log? more pics of pots?
Caution big brother is watching.
The beige is blinding!!!!!!
The middle of the road is boring

The true sign of intelligence is not knowledge but imagination.
-Albert Einstein

#17 timbo_heff

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Posted 17 June 2013 - 12:22 PM

"how much ash/glaze deposit was on shelf before? did you see shelves before firing?
how do the top of shelves look?
are shelves used one side up only?
have shelves been used in soda/salt firings?
was it all shelves or just a few?"

They are definitely old shelves: been fired many many times never in salt or soda: just lots of hot wood fires. These could be 20 years old or even more.
They were scraped pretty well: maybe not perfectly clean but not covered with old ash at all.
It was just these 1" ones that it happened to: the skinnier ones did not bubble and foam.

Schedule:
Candled for about 10 hours staying below 200F.
Then went 75 - 100 /hour til 06 down.
Then an hour or 2 of heavier reduction.
Then up to 2100F on the pyrometer for 30 hours until 11/12 down in front 9/10 in back:
Another heavy reduction cycle for a couple/ few hours.
held another 12 hours around 2150 on pyro.
Then we gently stuffed the kiln with big fat chunks to make some charcoal / charwood and sealed it up to hopefully get some slow reduction cooling.
Took about 4 days to get cool enough to open.

#18 TJR

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Posted 17 June 2013 - 01:04 PM

Timbo;
Can you send us some shots of the kiln,please. Your surfaces look great.I like the slab pot with the wads stuck to the side. Congratulations.
TJR.

#19 JBaymore

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Posted 19 June 2013 - 09:09 AM

Tim,

Are you POSITIVE that they have never been fired in soda or salt?

Many people who fire wood ALSO introduce soda or salt in the firing.

I have seen that kind of effect before with WET shelves (old... stored in damp conditions) that came from a salt kiln. The soda migrated to the surface as the shelf dried in the firing...and deposited on the surface (like with American Shino glazes) ande fluxed the silica in the SiC.

Any chance they were stored in a damp location near paper bags of soda ash or salt?

best,

...............john
John Baymore
Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

http://www.JohnBaymore.com




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