Karen Hamilton on sun 20 aug 06
My pottery teacher did a Raku firing yesterday and I was very pleased
with the results of my pieces. However, when I put them on the mantle
next to some pieces I did a couple of years ago, it was apparent that
the older pieces were not nearly as lustrous as the new ones. Why? The
old ones seem to have "faded" a little bit. I thought about using some
car wax to polish them up a little bit. Any thoughts on this?
Thanks.
--K
>
Bruce Girrell on mon 21 aug 06
Karen Hamilton wrote:
> ...it was apparent that the older pieces were not nearly as lustrous
> as the new ones. The old ones seem to have "faded" a little bit.
For a good discussion of this, see Tom Buck's article on the Digitalfire
website:
http://www.ceramic-materials.com/cermat/education/113.html
Tom proposes several improved glazes, some of which we have used with
success. We were particularly fond of Red Lustre #8.* YMMV.
> I thought about using some
> car wax to polish them up a little bit.
Without seeing the pots it would be hard to say. The metallic copper will
definitely buff up. Where I have seen a problem is in the remainder of the
glaze. The worst condition would be if the rest of the glaze is like a dry
copper matte. In that case, the polish gets in the innumerable tiny crevices
and remains there, giving a scummy white appearance as it dries. Perhaps a
follow-up scrubbing with lacquer thinner or something similar would help,
but don't count on it. The best case would be if the rest of the glaze is
glossy, without pinholing or crazing. Here the car wax can be cleaned off
properly after the cleanup of the metallic copper has been completed.
Some people have reported success in using a coat of a clear acrylic on
newly fired pieces to prevent oxygen from reaching the metallic copper thus
preventing the darkening. We have not tried this method.
* Red Lustre #8 uses red copper oxide. When making this glaze you need to
add some soap, like dishwashing liquid, to allow the red copper oxide to mix
in properly. It doesn't take much and don't expect all of the stuff floating
on the top to mix in.
Good luck!
Bruce "Thank you Tom!" Girrell
Craig Clark on mon 21 aug 06
Karen, this subject has been discussed at length on the list. There
is a healthy amount of information in the archives that will give you a
thourough understanding of the issue. Tom Buck, published a definitive
article on the subject back in the mid 1990's. His is the most
definitive read that I have come across. Just follow the link for a
complete explanatiion as written by Mssr. Buck.
http://ceramic-materials.com/cermat/education/113.html
The fading of Raku glazes is well known. The worst of the offenders
in the so called Copper Matt. It will fade pretty fast in humid climates
and is also photo reactive. A means by which to slow the degradation of
the glaze is to seal it. A friend of mine who does Copper Matts all the
time took to using grout sealer several years ago and says that it works
pretty well. He also tells his customers that this is not an archival
type of solultion. So far, there don't seem to be any, but perhaps
someone else on the list knows of one which will work over the long haul.
If someone trys to tell you that raku glazes, copper matts in
particular, do not fade, don't argue with them. They simply do not know
what they are talking about. Read what Tom Buck has to say and reference
the other posts as well as other articles. You will then be working from
a substantive knowledge base.
You will not generally encounter the same type of problem with a
white crackle, or other colored crackle which has a little more silica
and alumina than is in the conventional copper matt, or metallic looking
raku glaze. Keep in mind though that raku is not a vitrified clay body
and the glaze is fractured throughout. It is not meant to be used in a
functinoal, as in food service, manner.
If the glazes you used were of the "shiny metallic" variety, just
try taking them down and gently cleaning and then buffing them up a bit
again. You may get back some of the original luster.
Hope this helps
Craig Dunn Clark
619 East 11 1/2 St
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org
Karen Hamilton wrote:
> My pottery teacher did a Raku firing yesterday and I was very pleased
> with the results of my pieces. However, when I put them on the mantle
> next to some pieces I did a couple of years ago, it was apparent that
> the older pieces were not nearly as lustrous as the new ones. Why? The
> old ones seem to have "faded" a little bit. I thought about using some
> car wax to polish them up a little bit. Any thoughts on this?
> Thanks.
> --K
>
>
>>
>
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>
Joseph Herbert on mon 21 aug 06
Karen Hamilton wrote about Dulling Raku.
Karen, the only thing I don't understand about your post is the apparent
surprise at finding the raku had changed. Metal luster American "raku" is
the fraud of the craft pottery world. The "beauty" of the surface on the
"pots" is derived from the reduction of a metal to its unoxidized form or
nearly so. The glazes are compounded without much concern for stability
since they are intended to be attached by Carbon Monoxide to produce the
fabulous effects. Once the moment of fire and smoke is over, the "pot" is
continually immersed in an aggressive oxygen and sulfur containing soup (the
atmosphere) that works constantly to change the metal particles in the glaze
into oxides and sulfides. In a relatively short time, the metal particles
in the glaze begin to change.
An actual pot, prepared in the normal way using oxide materials for glazing,
will remain unchanged for thousands (certainly) or hundreds of thousands
(probably) or millions (it could happen) of years. Because of that,
uninformed persons may (wrongly) expect the same behavior from that shiny
thing they paid hundreds of dollars for.
American "Raku" sellers at craft fairs certainly will tell you (well, we
hope) to not eat off the "ware", may tell you to be careful of the surface,
and will universally neglect to say that it will remain unchanged only in an
inert atmosphere. Seems like I have seen very little of the really flashy
stuff in museums, probably a problem with conservation.
Actually I think the "Raku" process is fun and exciting and the unexpected
colorful results are a delight. I just think the objects resulting from the
process should be in a special category of ephemeral ceramics, like unfired
clay outdoor sculpture.
Joseph Herbert
Bunny Lemak on mon 21 aug 06
Last fall/winter I took a couple of raku classes and we used a Silicone
Grout Sealer, made by Tile Guard the clear kind (yes, there is also a
white) we bought it at Home Depot for about $3.00.
We only used it on the shiny copper raku pieces, you apply some with the
handy sponge applicator, let it set for a few minutes, then buff it out.
It "seals" the coppery colors.
I was also told that you can use this product again and again when the
copper starts to get cloudy, although it has been almost a year, my copper
glazes are still bright and shiny like last year. But.....I do not live
in a humid climate, so it may be different where you live.
My teacher also recommended sealing all raku with this product, including
the white crackle and the matte glazes.
Craig Clark on tue 22 aug 06
Joseph, I for one have been an seller of what you describe as
American Raku at craft fairs. You accuse me of being part of some type
of anomolous universal group who obviously don't know what we are
talking about, or worse, are somehow withholding vital information from
the buying public concerning the lack of archival quality inherent in a
Raku glaze. This is offensive.
I have not been a member of this so-called group at any point in my
professional carreer. I have sold several thousand raku pots and I can
unequivocally state that my clients are aware of the unstable quality of
the raku glaze, and that there will be a gradual change over time,
especially in the climate in which I recide which is quite humid. They
are also told, many times by me in adamant terms, that raku is for
DECORATIVE purposes only. It is NOT to be USED FOR FOOD SERVICE. I have
lost several sales because of this admonition. But I remain steadfast. I
don't know what "we" you are talking about - perhaps you are a
spokesperson for the greater clay community- but I trust this that this
information from atleast one of us scurroulous raku sales perps will let
you rest a bit earsier.
I know a number of other professional potters who are equally
forthcoming with information concerning raku glazes, even though this
has been a strain on their business in the case of the folks who had
almost exclusively focused on the copper matts. I have been to workshops
given by some of the best and brightest in the biz and the topic has
been openly discussed. So I'm not sure to which "universal group" you refer.
I was first introduced to the problem from a formal perspective when
reading the now famous article by Tom BUck. I don't know where you have
been, but this topic and direct reference has been discussed ad naseum
on this board by myself and many others. The archives are replete with
information on this very subject. Whenever someone who is new asks the
question I will point them in the direction of the Digital Fire Websight
and Tom Bucks article. Have you perhaps written any published material
on the subject that I can point inquiring minds toward?
As far as a "normal pot" being prepared in the "normal" way being
unchanged for thousands, if not more years, that depends. It is wholly
dependent upon whether or not the glaze is properly formulated and
whether or not it is a good fit with the clay body it is being used on.
I'll assume that you are referencing non reactive, stable and durable
glazes whithout acutally saying so for sake of discussion. If this is
the case, then you are correct. They'll take a lickin and keep on
tickin. However, if they don't fit right or are reactive then they too
will change. Just not nearly as fast as raku.
Just clarifying a few points
Craig Dunn Clark
619 East 11 1/2 St
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org
Joseph Herbert wrote:
> Karen Hamilton wrote about Dulling Raku.
>
>Karen, the only thing I don't understand about your post is the apparent
>surprise at finding the raku had changed. Metal luster American "raku" is
>the fraud of the craft pottery world. The "beauty" of the surface on the
>"pots" is derived from the reduction of a metal to its unoxidized form or
>nearly so. The glazes are compounded without much concern for stability
>since they are intended to be attached by Carbon Monoxide to produce the
>fabulous effects. Once the moment of fire and smoke is over, the "pot" is
>continually immersed in an aggressive oxygen and sulfur containing soup (the
>atmosphere) that works constantly to change the metal particles in the glaze
>into oxides and sulfides. In a relatively short time, the metal particles
>in the glaze begin to change.
>
>An actual pot, prepared in the normal way using oxide materials for glazing,
>will remain unchanged for thousands (certainly) or hundreds of thousands
>(probably) or millions (it could happen) of years. Because of that,
>uninformed persons may (wrongly) expect the same behavior from that shiny
>thing they paid hundreds of dollars for.
>
>American "Raku" sellers at craft fairs certainly will tell you (well, we
>hope) to not eat off the "ware", may tell you to be careful of the surface,
>and will universally neglect to say that it will remain unchanged only in an
>inert atmosphere. Seems like I have seen very little of the really flashy
>stuff in museums, probably a problem with conservation.
>
>Actually I think the "Raku" process is fun and exciting and the unexpected
>colorful results are a delight. I just think the objects resulting from the
>process should be in a special category of ephemeral ceramics, like unfired
>clay outdoor sculpture.
>
>Joseph Herbert
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
>
>
>
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