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Ryan_pelo

How To Start Making My Own Wood Ash Glaze

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I want to try making my own wood ash glaze, but every batch of wood ash is unique and will yield different results, so I think using an exact recipe from online would just be a waste of time. Digitalfire tells me that it takes some experimenting to find the perfect balance of chemicals that works for you, but I don't know where to start.

 

Is there a general rule that I should follow for wood ash glazes like there is for regular glazes? My ceramics teacher has a paper from Roy and hasselberth that shows a reccomended range of concentrations for silica, fluxes, etc. Following these guidelines pretty much guarantees a stable and food safe glaze. There's also commonly known base glazes for regular glazes that are very stable and works every time, like the 5x20 base. Are there any broad/general rules that should be followed for wood ash glazes, for example something like "the concentration of wood ash should be at least 50%"? Any well known stable base glazes for wood ash glazes? Otherwise I have pretty much nothing to go off of and I would be randomly mixing chemicals with no idea of what to add. Thanks for any help you can give

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What cone? What firing type? Are you looking to simply use wood ash as a calcium source, or the runny rivulet type? Why do you want to use wood ash? You can formulate a glaze with the same properties by using other easier-to-use materials.

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If you are firing to cone 9-10 .......... try doing a triaxial blend with the following three ingredients at the points of the blend:

 

Wood ash

Any feldspar

Any clay

 

 

For a typical starting point.......

 

1/3 Wood Ash

1/3 Any Potash Feldspar

!/3 Any Ball Clay

 

 

You can modify the above starting point................

 

1/3 Wood Ash

1/3 Nepheline Syenite

1/3 Any Ball Clay

 

And also..........

 

1/3 Wood Ash

1/3 Any Potash Feldspar

1/3 Redart (or Newman Red, or Sheffield Slip, or Alberta Slip)

 

best,

 

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

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Type in  "How to make Cone 6 Wood Ash Glazes" in your search and you will come up with a lot of recipes.  I fire to cone 6 and tried to make a wood ash glaze and always came up with a greenish brown muddy color that didn't flow well.  But it doesn't hurt to try, you will learn something about making glazes.  Make sure you put a cookie under your test pieces you don't want the glaze running on to the kiln shelf and ruining it.  Potter

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John, Did you mean 1/3 Redart or Alberta in your last recipe instead of the 1/4 that you mentioned?

 

OOPS!   Typo.  THANKS, Fred.  Can't have 1/3 + 1/3 + 1/4..... it leaves a bit missing.

 

I'll go edit that to 1/3 (like it should be.)

 

best,

 

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

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RYAN, if your work is fired to cone 6 in a group setting, i suggest you talk to the person who fires the kiln about the possibilities of getting more glaze choices.  introducing a glaze that is likely to run all over the shelves in a group studio is not something you will enjoy.  since you are using glazes you mix, why not start with some color modification of that 5x20 glaze you already have?  that is a simple step and might result in a good glaze for everyone to use.

 

 

there is a very interesting glaze for cone 6 called "fake ash glaze" that takes different colors and gives the running that you mention.  i have that recipe in my glaze book but will not have access to it until the end of april.  perhaps someone else has it and will share it here.

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Collecting and processing enough wood ash is a lot of work. Using actual wood ash is a good exercise in ceramic knowledge, but I would not want to be the one in charge of maintaining wood ash glaze for a community studio. For your own use, fine. But not for everyone else, especially because it will probably be a popular glaze if the current choices are limited as you say. A runny rivulet wood ash glaze is high calcium, low alumina and silica, and can be formulated without any actual wood ash. Google 'Fake Ash Glaze' and you'll find plenty of options that are no more work than any other glaze. And as others have said, double check with your teacher that it's okay to put in the studio because they are runny and very likely to end up on the kiln shelves.

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Thanks to you all for the input...

I have a 33 gal trash can full of unprocessed wood ash and a 5 gallon bucket of screened ash. I was thinking that some time down the line I might try making my own glaze just to see how it would turn out. With your input, I've decided to just use the ash in my garden, instead!

JohnnyK

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I've tried a few recipes with wood ash (have a plentiful supply), but at ^6 they didn't work well.  Dry and crusty.  Hoping to try some again at summer camp at a higher cone.

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One tp I've found is not to wash the ash. It is a lot of work, and removes soluble fluxes. Unwashed ash glazed generally have a halo round the edge of the glaze, but I don't mind that, and although a bit more caustic putting on a pair of gloves is a lot less work than washing the ash!

Perhaps try it on the inside of a bowl, so it won't run off the pot and upset the others in the studio!

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There was a glaze heading in the www.potters.org site long ago when it existed... There was a fake ash glaze recipe there... Pick an easy ash glaze to try then experiment... Then branch out from there...

 

Alabama

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I have been in Japan for many years working with ash glazes.   Most Japanese clear glazes are simply wood ash and feldspar, which are locally dug and known only by that location's name; there is not a great variety in their effects.  In the local ceramics supply store there are test tiles that (A) range from pure feldspar to pure wood ash, generally 10% difference (so 9:1, 8:2, 7:3).   The type of ash matters more than the feldspar, however all seem to work well.  In Mino and Seto the ash of chestnut bark is held in high regard, and in Oita Prefecture Oak ash is particularly esteemed.  

 

My own experience is that (A) the ash/feldspar balance has mostly to do with the temperature to which one plans to fire, and (B) the atmosphere, firing schedule, and interaction with the clay body have much more effect upon the outcome than type of ash, feldspar, and balance of the two.

 

I was in Hagi recently, and spoke at length with Takeshi Kaneko, a highly respected potter.  In Hagi ware, the glaze is usually 50/50 ash and feldspar (by weight).  He uses the ash of the autumn leaves, generally Japanese chestnut, but only because they are plentiful and he needs to burn them anyway.  Although most Japanese fire glazes to 1230 degrees celsius, Hagi ware is fired to only 1200 degrees in a slightly reducing atmosphere, five hours up, five hours down.  If over-fired all of the beautiful effects ("gohonde") is lost, making boring surfaces.  The 50% ash content is required to flux the glaze to mature at the lower temperature.

 

In wood-fired kilns that seek a natural ash glaze from the firing itself, red pine is the primary fuel, but this because it burns hot and fast; they tend to finish off the firing with hard woods such as oak or elm for effects.  The process means that most of the ash in the ash pit is from pine, and so much of the mixed-and-applied ash glazes tend to have a lot of pine ash in them.   

 

  Alex Wilds, Kofu, Japan

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