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Nuka glaze - what is it?

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I keep seeing the description "nuka glaze" on pieces I admire - a creamy white high fire glaze. Is nuka a kind of ash? I'd love to find a mid range recipe for this type of glaze but it probably doesn't exist...

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It's a soft, white-grey semi matt glaze. It does contain wood ash. I will post a recipe when I get to the studio.

John Baymore would be able to tell us more about it.

TJR.

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Writing from NCECA.....working totally from memory here.... my glaze file is not here.

 

"Nuka" is the Japanese word for the husk (or hull) of the rice kernel. It is a by-product of the milling of white rice. The Japanese version is from a short grain rice.

 

Potter parlance (in Japanese) uses this term for glazes based upon rice HUSK ash (not rice straw ash....... different chemical composition). The agricultural waste is piled in the fields and is then burned. The piles smolder more than burn, and a good ash for glaze use is actually dark grey to black. You don't want it to burn cleanly. This color comes from carbon residue in the ash. SO the ash has a high L.O.I. The chemical composition of rice husk ash (after L.O.I.) is almost colloidally fine silica. (TJR I'd call it more of a semi-gloss.)

 

Nuka glazes are high calcium fluxed glazes (from the washed wood ash) what use the rice husk ash for a lot of the silica content, and bringing in the silica in a very fine particle size. They fire a bluish white and are slightly milky opaque where thicker due to the unmelted silica particles.

 

I use real rice husk ash (imported and expensive) and washed hardwood ash. Firing it from Orton cone 10 to Orton cone 14. The recipe I started with I got from Hamada Shoji-sensei.

 

1/3 rice husk ash

1/3 wood ash

1/3 terayama stone ( a high silica bearing feldspathoid)

 

 

That is modified for more locally available materials as...............

 

 

32% rice husk ash

 

32% wood ash

 

32% Custer feldspar

 

4% flint

 

This stuff is natural material glaze.... the slurry handles VERY differently from what most people are used to when ucing commercial beneficiated materials. It looks REALLY thick when on the proper consistency, and is sort of "fuzzy" looking. It setles down in firing due to the high L.O.I. of the rice husk ash.

 

Hope this is of use.

 

 

best,

 

...................john

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Writing from NCECA.....working totally from memory here.... my glaze file is not here.

 

"Nuka" is the Japanese word for the husk (or hull) of the rice kernel. It is a by-product of the milling of white rice. The Japanese version is from a short grain rice.

 

Potter parlance (in Japanese) uses this term for glazes based upon rice HUSK ash (not rice straw ash....... different chemical composition). The agricultural waste is piled in the fields and is then burned. The piles smolder more than burn, and a good ash for glaze use is actually dark grey to black. You don't want it to burn cleanly. This color comes from carbon residue in the ash. SO the ash has a high L.O.I. The chemical composition of rice husk ash (after L.O.I.) is almost colloidally fine silica. (TJR I'd call it more of a semi-gloss.)

 

Nuka glazes are high calcium fluxed glazes (from the washed wood ash) what use the rice husk ash for a lot of the silica content, and bringing in the silica in a very fine particle size. They fire a bluish white and are slightly milky opaque where thicker due to the unmelted silica particles.

 

I use real rice husk ash (imported and expensive) and washed hardwood ash. Firing it from Orton cone 10 to Orton cone 14. The recipe I started with I got from Hamada Shoji-sensei.

 

1/3 rice husk ash

1/3 wood ash

1/3 terayama stone ( a high silica bearing feldspathoid)

 

 

That is modified for more locally available materials as...............

 

 

32% rice husk ash

 

32% wood ash

 

32% Custer feldspar

 

4% flint

 

This stuff is natural material glaze.... the slurry handles VERY differently from what most people are used to when ucing commercial beneficiated materials. It looks REALLY thick when on the proper consistency, and is sort of "fuzzy" looking. It setles down in firing due to the high L.O.I. of the rice husk ash.

 

Hope this is of use.

 

 

best,

 

...................john

 

 

 

 

Thank you very much. Extremely informative. What is L.O.I.?

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Loss On Ignition. It is the difference in molecular weight when the material has been heated up to reactive temperature / oxidized in the kiln and the starting molecular weight In this case carbonaceous matter gets turned to CO2 and things like carbonates give up the CO2.

 

best,

 

....................john

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saw something the other day about rice husk being a waste product from milling in California rice production. I had have to google to find it but will look into it later.It's being re purposed into something, forget what???

 BTY John what about Michael Coffee's Nuka

  • Custer Feldspar    36.00
  • Quartz   30.00
  • Whiting   22.00
  • OM-4   6.00
  • Wood Ash (unwashed)   3.00
  • Talc   2.00
  • Bone Ash   2.00

http://dmichaelcoffee.wordpress.com/2010/07/27/nuka-glaze-recipe-%E2%88%8610-reduction/

 

Notes: This a ∆10 Reduction glaze that will fire to a Creamy White with low gloss to satiny finish. Good over tenmoku, will run if applied too thick over thick tenmoku. As always, test for your ingredient and firing conditions.

 

I use on version that breaks white/green on top of a rutile blue

 

have to look for it later

 

Wyndham

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Thanks Wyndham for the recipe. I have seen this before but I completely forgot about it! I like that this glaze is not shiny white but rather satin white. Now I would just need to find wood ash. No one here in MN seems to have any for me, and I don't have a fire pit. 

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Wyndham,

 

That glaze recipe above is what you might call a 'synthetic nuka'.  Similar look.  I believe that a number of potters have their name on variations of that kind of glaze.

 

I've been in contact with a US supplier of by-product rice husk ash from electric generation.  Unfortunately to work well for a glaze, it reallty has to be burned in a certain way.  That stuff is not.  Would likely require a lot of "processing" on the user's end to get it suitable.

 

best,

 

..............john

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Phil,

 

As mentioned way above..... I import it.  And it is the most expensive glaze ingredient I buy because of that.  But the real thing and the synthetic recipes do look different if you are looking closely.  I reserve it almost 100% for Chawan.

 

It is the burnerd ash... not the husks.  The husks burn down a huge amount (probably 80 percent)..... so while light... they are voluminous and would be crazy to ship.

 

best,

 

..................john

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Wyndham,

 

 

I've been in contact with a US supplier of by-product rice husk ash from electric generation. Unfortunately to work well for a glaze, it reallty has to be burned in a certain way. That stuff is not. Would likely require a lot of "processing" on the user's end to get it suitable.

 

best,

 

..............john

This may be a silly question....But... do you know what is the special way to burn the husks? I'd like to refine my tumbleweed ash a bit to improve my ash glaze.

 

Jed

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Jed,

 

Because the husks in a pile are so dense... unlike your relatively open tumbleweeds....... getting air into the pile is the issue for burning.  Usually a sort of a metal chimney is imbeded into the pile and moved around.  The piles 'smoulder' rather than a real "burn" really.  For the glazes... it needs to be burned so that it is partially burned.... and is pretty much black or dark grey.  Huge LOI when the glaze is fired.

 

best,

 

.................john

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This may be a silly question....But... do you know what is the special way to burn the husks? I'd like to refine my tumbleweed ash a bit to improve my ash glaze.

 

Jed

 

 for burning brush. Seems like a great idea!

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is it possible to use rice husk from a local rice farmer and burn your on to make your ash. the rice grown here in Louisiana is white rice. The rice fields are burned when finished in the fall so getting the husk would be no problem

Edited by pmeredith

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