Alisa Clausen on wed 8 sep 04
Dear Clayart,
I am looking for a reason that my wheel head seems to "produce" a dark =
gray slip when I throw.
I have a Brent CXC that is about 5 years old. The wheel head shows a =
little wear around the outside edge, where there are small areas of =
abrasion in the top layer of the surface. The top part of the wheel =
head shows very little abrasion marks.
About 2 months ago, I decorated pots on the bare wheel head with blue =
slip. I thought that there must be still slip in the grooves of the =
wheel head that was getting wet and coloring the throwing slip, every =
time I threw. I cleaned the wheel thoroughly several times. When I =
throw, there is a dark gray color in the slip from the throwing. I kept =
thinking it is still cobalt, but I would be surprised if there is cobalt =
slip somewhere on that wheel. I have thrown many times since I have =
decorated with the blue slip, and continue to clean the wheel. =20
When I throw, there is sometimes friction on the edge of the wheel =
head's side and my clothing. The dark gray slip is very noticeable on =
my clothing when I lean over to far and my clothing touches the moving =
wheel head.
I cannot remember this from ever before. Can it be friction from the =
worn areas on the wheel head and something in the layer under the first =
layer of metal of the wheel head that makes this dark slip. It annoys =
me. It gets on everything, although it does wash away. I am going to =
fire some of this slip just to see if it colors the clay. Could Cobalt =
hang around that long?
Any ideas what it causing this is appreciated. (This could also start a =
thread of chillers and thrillers from the dark corners of the studio.)
regards from Alisa in Denmark
Wayne on wed 8 sep 04
Alisa:
I noticed the same thing, not only on my wheelhead, but also coming from the
pugmill
which is cast aluminium. I noticed it was most prevalent while using a very
white cone 10
porcelain.
I spoke to the pugmill folk, and also a friend who is a metallurgist. The
general consensus
is that it is either some sort of "reaction" between the clay body and the
aluminium, or it is some sort of an algae or bacteria forming in the clay
slip. ( I also notice it on the bottom of my throwing
bowl). True that aluminium will oxidize grey...my first thought.
It does not appear to affect the properties of the clay, it does not smell,
and it does not show
once fired. I am slightly concerned about the "addition" of aluminium as
regards glaze and fluxing
but so far, I have not noticed any problems. Of course, I'm not sending my
glazes through the pugmill
Hope that helps,
Wayne Seidl
- Original Message -----
From: "Alisa Clausen"
To:
Sent: Wednesday, September 08, 2004 2:52 AM
Subject: Monster from the Blue Lagoon lives in my wheel head.
Dear Clayart,
I am looking for a reason that my wheel head seems to "produce" a dark gray
slip when I throw.
I have a Brent CXC that is about 5 years old. The wheel head shows a
little wear around the outside edge, where there are small areas of abrasion
in the top layer of the surface. The top part of the wheel head shows very
little abrasion marks.
About 2 months ago, I decorated pots on the bare wheel head with blue slip.
I thought that there must be still slip in the grooves of the wheel head
that was getting wet and coloring the throwing slip, every time I threw. I
cleaned the wheel thoroughly several times. When I throw, there is a dark
gray color in the slip from the throwing. I kept thinking it is still
cobalt, but I would be surprised if there is cobalt slip somewhere on that
wheel. I have thrown many times since I have decorated with the blue slip,
and continue to clean the wheel.
When I throw, there is sometimes friction on the edge of the wheel head's
side and my clothing. The dark gray slip is very noticeable on my clothing
when I lean over to far and my clothing touches the moving wheel head.
I cannot remember this from ever before. Can it be friction from the worn
areas on the wheel head and something in the layer under the first layer of
metal of the wheel head that makes this dark slip. It annoys me. It gets
on everything, although it does wash away. I am going to fire some of this
slip just to see if it colors the clay. Could Cobalt hang around that long?
Any ideas what it causing this is appreciated. (This could also start a
thread of chillers and thrillers from the dark corners of the studio.)
regards from Alisa in Denmark
____________________________________________________________________________
__
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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.
Scott Paulding on wed 8 sep 04
I've also noticed it on wheelheads that are metal, but never on plastic ones. I
always assumed it was an oxide of the metal on the wheel washing off (sometime,
try taking a clean spounge and clean H2O to it and see if the water turns
grey/black after you wringe the spounge out in it).
It gets into the slip and reclaim, but never seems to be an issue.
-scott
--- Alisa Clausen wrote:
> Dear Clayart,
> I am looking for a reason that my wheel head seems to "produce" a dark gray
> slip when I throw.
>
> I have a Brent CXC that is about 5 years old. The wheel head shows a little
> wear around the outside edge, where there are small areas of abrasion in the
> top layer of the surface. The top part of the wheel head shows very little
> abrasion marks.
>
> About 2 months ago, I decorated pots on the bare wheel head with blue slip.
> I thought that there must be still slip in the grooves of the wheel head that
> was getting wet and coloring the throwing slip, every time I threw. I
> cleaned the wheel thoroughly several times. When I throw, there is a dark
> gray color in the slip from the throwing. I kept thinking it is still
> cobalt, but I would be surprised if there is cobalt slip somewhere on that
> wheel. I have thrown many times since I have decorated with the blue slip,
> and continue to clean the wheel.
>
> When I throw, there is sometimes friction on the edge of the wheel head's
> side and my clothing. The dark gray slip is very noticeable on my clothing
> when I lean over to far and my clothing touches the moving wheel head.
>
> I cannot remember this from ever before. Can it be friction from the worn
> areas on the wheel head and something in the layer under the first layer of
> metal of the wheel head that makes this dark slip. It annoys me. It gets on
> everything, although it does wash away. I am going to fire some of this slip
> just to see if it colors the clay. Could Cobalt hang around that long?
>
> Any ideas what it causing this is appreciated. (This could also start a
> thread of chillers and thrillers from the dark corners of the studio.)
>
> regards from Alisa in Denmark
>
>
______________________________________________________________________________
> 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.
>
=====
"I should have been a plumber."
-Albert Einstein
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Anne Webb on wed 8 sep 04
same thing happened to me re the dark grey slip. i never much worried about
it but i did notice that my wheelhead is not as shiney as it was when i
first got it, no matter how much i cleaned it. never able to wipe it down,
particularly in those grooves, without getting dark grey sludge on my
sponge.
might be related to exposure to water...? seems tin foil (aluminum foil)
goes grey when its exposed to water or condensation.. you know like when you
cook some food and cover it with tin foil while the food is still warm. the
condensation seems to make the foil discolours to a kinda dark grey. maybe
edouard or tom can say what is going on and why this chemical reaction
happens...? perhaps the addition of clay (abrasive) causes a layer of it
to come off....?
be interesting to hear what they have to say.
anne
,,,not looking forward to ivan coming into the gulf. could be us next :(
>From: Wayne
>Reply-To: Clayart
>To: CLAYART@LSV.CERAMICS.ORG
>Subject: Re: Monster from the Blue Lagoon lives in my wheel head.
>Date: Wed, 8 Sep 2004 07:39:03 -0400
>
>Alisa:
>I noticed the same thing, not only on my wheelhead, but also coming from
>the
>pugmill
>which is cast aluminium. I noticed it was most prevalent while using a
>very
>white cone 10
>porcelain.
>I spoke to the pugmill folk, and also a friend who is a metallurgist. The
>general consensus
>is that it is either some sort of "reaction" between the clay body and the
>aluminium, or it is some sort of an algae or bacteria forming in the clay
>slip. ( I also notice it on the bottom of my throwing
>bowl). True that aluminium will oxidize grey...my first thought.
>It does not appear to affect the properties of the clay, it does not smell,
>and it does not show
>once fired. I am slightly concerned about the "addition" of aluminium as
>regards glaze and fluxing
>but so far, I have not noticed any problems. Of course, I'm not sending my
>glazes through the pugmill
>
>Hope that helps,
>Wayne Seidl
>
>- Original Message -----
>From: "Alisa Clausen"
>To:
>Sent: Wednesday, September 08, 2004 2:52 AM
>Subject: Monster from the Blue Lagoon lives in my wheel head.
>
>
>Dear Clayart,
>I am looking for a reason that my wheel head seems to "produce" a dark gray
>slip when I throw.
>
>I have a Brent CXC that is about 5 years old. The wheel head shows a
>little wear around the outside edge, where there are small areas of
>abrasion
>in the top layer of the surface. The top part of the wheel head shows very
>little abrasion marks.
>
>About 2 months ago, I decorated pots on the bare wheel head with blue slip.
>I thought that there must be still slip in the grooves of the wheel head
>that was getting wet and coloring the throwing slip, every time I threw. I
>cleaned the wheel thoroughly several times. When I throw, there is a dark
>gray color in the slip from the throwing. I kept thinking it is still
>cobalt, but I would be surprised if there is cobalt slip somewhere on that
>wheel. I have thrown many times since I have decorated with the blue slip,
>and continue to clean the wheel.
>
>When I throw, there is sometimes friction on the edge of the wheel head's
>side and my clothing. The dark gray slip is very noticeable on my clothing
>when I lean over to far and my clothing touches the moving wheel head.
>
>I cannot remember this from ever before. Can it be friction from the worn
>areas on the wheel head and something in the layer under the first layer of
>metal of the wheel head that makes this dark slip. It annoys me. It gets
>on everything, although it does wash away. I am going to fire some of this
>slip just to see if it colors the clay. Could Cobalt hang around that
>long?
>
>Any ideas what it causing this is appreciated. (This could also start a
>thread of chillers and thrillers from the dark corners of the studio.)
>
>regards from Alisa in Denmark
>
>____________________________________________________________________________
>__
>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.
>
>______________________________________________________________________________
>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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Laurie Kneppel on wed 8 sep 04
Hi Alisa and Wayne,
I have a Brent C and I get the same gray goo once in awhile. I notice
it only appears with certain claybodies and if I am really feeling grit
on the wheelhead as I throw, so it must be an ingredient in the clay
perhaps causing the aluminum to oxidize or abrade slightly? It doesn't
seem to hurt or change anything, but I suppose if it was a problem,
then throwing those claybodies on a bat ought to solve it. I think I
have noticed it most with white stoneware or maybe it was a cone 10
porcelain? I will pay attention next time and remember which clay did
it.
The only creepy things in my studio - so far - are some mice and
spiders!
And sometimes the gunk in the slurry bucket.
Laurie
Sacramento, CA
http://rockyraku.com
Potters Council, charter member
Sacramento Potters Group, member
Bruce Girrell on wed 8 sep 04
It is aluminum. Just plain aluminum. Very fine, plain old aluminum.
If it gets in your clay it will oxidize to a tiny amount of (white) aluminum
oxide when fired and you'll never see it.
Bruce "another deep mystery solved" Girrell
Christy Pines on wed 8 sep 04
If you cook in aluminum pans and make a "roux" - butter and flour and milk as the start of a sauce - you may find that roux is not nice and white/butter colored but can be rather grey. From the aluminum.
I have always assumed that the greyness that comes off on my sponge as I clean the sides of my Brent wheelhead (which is aluminum) is caused by the same thing - aluminum.
christy in connecticut
cpines at ix.netcom.com
Alisa Clausen wrote:
I am looking for a reason that my wheel head seems to "produce" a dark gray slip when I throw.
I have a Brent CXC that is about 5 years old. The wheel head shows a little wear around the outside edge, where there are small areas of abrasion in the top layer of the surface. The top part of the wheel head shows very little abrasion marks.
Earl Krueger on thu 9 sep 04
Alisa,
I predict that the result of your experiment firing the
gray goop will result in something that looks just like
your fired clay. The aluminum will oxidize to white
alumina, even in a reducing atmosphere.
If you could separate out the gray matter from the
rest of what's in the goop you would find that it is a
pretty miniscule amount. If it weren't you would soon
wear down your wheel head to a nubbin. I will also
predict that it won't noticeably affect your clay or glaze.
Except .....
Finely divided aluminum metal is such a strong
reducing agent that when combined with iron oxide and
ignited the iron oxide will be reduced to iron metal and
the heat generated will melt, not only the iron, but the
aluminum oxide. The mixture is known as thermite.
I wonder if putting aluminum powder in a glaze and
firing in an oxidation atmosphere would result in
reduction effects in the glaze? Care to try it?
Anybody thinking of trying this needs to be very, very
cautious as aluminum powder is an extreme fire hazard.
Earl K...
Bothell, WA, USA
Bonnie Staffel on thu 9 sep 04
Dear Alisa,
It is my opinion that your wheelhead is made of aluminum. Perhaps the metal
was coated with a (shellac) or some such covering when it was new. Abrasion
would wear it away, leaving the bare metal.
Also if you have ever noticed, if you cook potatoes in an aluminum pan, they
will turn dark. Some acid foods react with aluminum utensils. Not a good
idea healthwise, IMHO.
Whether the aluminum oxide will react physically in your slip as to color or
melting properties, it might be a good experiment.
Regards,
Bonnie Staffel
http://webpages.charter.net/bstaffel
http://www.vasefinder.com/
Potters Council member
william schran on thu 9 sep 04
Alisa wrote:> I am looking for a reason that my wheel head seems to
"produce" a dark gray slip when I throw.<
it's aluminum oxide, anything that applies pressure to the wheel head
will abrade slightly and produce the dark grey aluminum oxide.
Bill
Alisa Liskin Clausen on thu 9 sep 04
Dear Clayart,
Thank you for all of the responsed to my query. I have not seen any
changes whatsoever in my fired ware from this aluminum slip. However, what
is elemenatry to some of us on the list, has been irking me for a short
time. I had a very vague idea that it came from abrasion of the first
layer on the wheel head, but had not thought about what the wheel head was
made of and do not know much about aluminum's tarnishing properties.
Since Claus man is also cook man, I have not cooked in any aluminium pans
or such, so had not made any connections. I have some glob to fire for
curiosity sake, as well as try throwing also with distilled water and
different clays. I think with the darker clays I just cannot see the gray
color. I always like a reason to make an experiment.
Thanks Clayart. Great to have a living book where we can look up anything
from starting out, to way up there.
regards from Alisa
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