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processing wood ash

updated fri 26 mar 04


Marc Hudson on thu 25 mar 04

John Kudlacek, Carole Fox, Carol Metcalfe, and Randy McCall,

I hope this won't be too long a reply, but here goes!

I guess I should begin near the beginning of my appreciation and interest=
developing ash glazes. I became interested in Eastern and Middle Eastern=
Ceramics. I took a couple of ceramic classes from Alfred trained Stan=20
Zelinski at the University of Alaska, Fairbanks in the early 1970=92s (I =
now a lot of my clay shapes seem to have an Eastern and Middle Eastern fe=
to them). I experimented with coal ash from the stove in my cabin in the=
woods. I didn=92t know enough about glaze make-up to moderate the rapid =
flow at ^10, so many pots had lids stuck on and often stuck on kiln shelv=
es. =20
I was discouraged, so I turned my attention to Raku glazes and firing=20
techniques instead. It was another 20 years before I picked up the glaze=
ash glaze torches and began to research and experiment once a again.

As my current studio is a single car garage converted to a ceramics and=20
woodworking studio. Here =93converted=94 means no car comes in and every=
surface (including the ceiling) is used for storage! As I have no room f=
or a=20
wood or gas fired kiln, my choice for firing was an electric kiln (Skutt =
15 years old) which I fire regularly. I use the kiln sitter with small c=
and never set the two dials above =935=94, this gives a slow heat ramp up=
to ^6=20
(about 7 hours). I keep the top three peepholes plugged and the bottom=20
peephole unplugged during bisque and glaze firing. In my mind this still=
permits out-gassing and keeps the heat, which rises up anyway in the kiln=
the kiln, (I don=92t know if this is true or not, but it seems to work!).

My wood ash comes from a friend=92s fireplace and aside from scrap constr=
lumber, I don=92t know what materials he might burn on any given cold win=
night. I figure not knowing adds a certain serendipity to my glazes! =20

The ash is first sifted (outside) through fabric paint filters in one of=20
those lidded, 5 gallon white buckets until I have a fine dust void of=20
charcoal, nails and screws! I guess the mechanical designer in me couldn=
resist the temptation to develop a motor driven shaker so I could be doin=
something else useful while the ash was sifting!

With the sifting finished, the bucket of ash is filled with water to the=20
brim, stirred vigorously and left outside overnight to soak and wash. Th=
next day, the water/lye solution is carefully poured into a concrete basi=
n to=20
evaporate (loosely covered to keep pets away), and the bucket is refilled=
with water, stirred again, and left outside overnight to soak and wash. =
never have to touch the liquid lye. Two soakings seems to be enough.

After the water solution is poured off a second time, the slurry is poure=
into a dryer. Again, mechanical designer in me couldn=92t resist the=20
temptation to develop a fan driven dryer out of horizontally placed 4=94 =
pipe with vertical elbows at each end. The pipe is half filled with the =
slurry, a small fan is mounted to one elbow sucking air out of the pipe, =
the slurry is dried (takes a couple of days). The ash dries to a chalky =
consistency, at which time the cake is broken into small pieces, removed =
the drier and the process is repeated until all the slurry is dried. The=20
pieces of dried cake are broken into a powder (using a stick), stored in =
gallon white buckets, and are ready for glaze testing.

I have several books that have helped me enormously in understanding glaz=
materials interactions:
=93Ash Glazes=94 by Robert Tichane, =93Ash Glazes=94 by Phil Rodgers, =93=
Ceramics=94 by=20
Glen Nelson, =93Mastering Cone 6 Glazes=94 by John Hasselberth and Ron Ro=
y, and=20
John Hasselberth=92s GlazeMaster 2.0 computer software. This is by no me=
ans an=20
exhaustive list of reference materials, these are just the books I have=20

If you have and John Hasselberth=92s GlazeMaster 2.0 computer software, a=
happen to plug in my ash glaze recipe, you will find it does not come=20
anywhere close to John Hasselberth and Ron Roy=92s recommended alumina an=
silica content. I have tried to raise both alumina and silica content, o=
to find I loose the drippy quality I like so much. Therefore, I would=20
recommend using my ash glaze on the outside of functional or on non-
functional pieces. I have many ash-glazed bowls with liner inside at hom=
that I have used for years in the kitchen and washed in the dishwasher. =20
These bowls have shown no ill effects over the years from the high heat a=
soap environment. Nevertheless, err on the side of caution, this glaze=20
probably will not pass the lime juice or steel knife tests.

I made a die for my North Star extruder that makes a modified =93L=94 sha=
pe that=20
is cut into 1=BC=94 widths, numbered sequentially, and drilled for string=
ing up=20
later. These are my glaze test tiles. I prepare about 150 at a time for=
quick and easy, spur of the moment glaze tests. When I am finished with =
25 =96
30 tests, the tiles are strung in a loop of bailing wire, and hung from t=
ceiling for storage and future reference.

Well, there you have it. There is my secret to the ash glazes you see on=
web site. I hope this much too long treatise helps dispel some of the=20
mystery of wood ash glazes.

---------- Original Message -----------
From: jklay
Sent: Wed, 24 Mar 2004 08:31:18 -0600
Subject: Ashes

> Ash Glazer Wanabees and Marc
> I have used ash for glazes (50% ash) for years and remember early=20
> experiences washing ash. Marc Hudson states that he washes his=20
> ashes twice since he did not like the contact with the lye. I quit=20
> washing ashes "because I "did not like the contact with the lye". =20
> It literally turned my epidermis into soap. Please explain how you=20
> go about washing the ash with out contacting lye. The obvious=20
> answer must be "gloves". Then, drying the ash is another problem.=20
> When I use my ash glaze I keep my hands out of the mix and=20
> incidental contact has no ill affect. Recently I have been calcining=20
> my ash and am pleased with the results. It obviously results in more=20
> consistency as the amount of charcoal is essentially reduced to=20
> zeroe. Soooo... I recommend taking the W out of "wash" and you end=20
> up with just A-S-H. It works for me.
> John Kudlacek
> Topeka
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------- End of Original Message -------