mel jacobson on sun 22 feb 04
Shimpo Wheel Woe (cute, huh?)
I just purchased a Shimpo VL Whisper and it's a great wheel, EXCEPT that,
as I began centering my first lump of clay, I noticed that black residue
had stained my left hand where it contacted the wheel. I removed the clay
and carefully wiped the head with a damp cotton cloth and warm water. The
white cloth I used turned black! The residue washes out in water (turning
the water gray), but each subsequent cleaning kept turning my cloth blacker
and blacker, like I was kicking black pigment out of the wheelhead grooves.
After about 5 vigorous rubbings with cloth and a sponge, the black mess is
no better. Because I wanted to test the wheel, I returned to throwing my
white earthenware. The black comes off on whatever contacts the wheelhead
surface (my hand or sponge) and then gets into the clay, staining it. It
seems worse when I rub in the direction of the grooves, as opposed to
across them.
Now I have 25 lbs. of stained gray clay sitting on my worktable. Some of it
is formed, some in a reclamation bucket, and some in a slop bucket; all
gray and not the bright white it was. What is this black stuff? Will it go
away? Will it ruin the white color of the clay in the bisque fire? Shall I
fire the stained pieces, or toss all the tainted clay, slop and all?
Thank you! Sorry to mail to this you directly.
Melissa Jeswald Dec"mjd2361" on Yahoo!
From:
Minnetonka, Minnesota, U.S.A.
web site: my.pclink.com/~melpots
or try: http://www.pclink.com/melpots
new/ http://www.rid-a-tick.com
Bruce Girrell on sun 22 feb 04
> ...as I began centering my first lump of clay, I noticed that black
residue
> had stained my left hand where it contacted the wheel.
> The residue washes out in water (turning the water gray), but each
> subsequent cleaning kept turning my cloth blacker and blacker,
> like I was kicking black pigment out of the wheelhead grooves.
It sounds as though you're throwing directly on the wheelhead, which is
almost certainly made from aluminum. If so, you are seeing aluminum. I know,
aluminum is gray and what you see is black, but trust me, it's aluminum.
Get some bats and your problem will go away. As for any pieces that you may
have already made, the aluminum will oxidize in the bisque and turn white.
Bruce Girrell
in almost warm (34 degrees) northern Michigan
with the Stak-O-Brix cooling after a smooth trip to cone 10. We're still
getting used to high fire, having gotten accustomed to the immediate
gratification of low fire. Now I understand all those "how soon can I open
the kiln?" questions.
william schran on tue 24 feb 04
Melissa wrote:>as I began centering my first lump of clay, I noticed
that black residue
had stained my left hand where it contacted the wheel. <
It's aluminum oxide and you will always have it since the wheel head
is made of aluminum. The only solution is to stop pressing down so
hard on the wheel head with your hand, sponge or whatever. Especially
when centering, rest your arms on your legs and your hands on the
clay. Your hands can contact the wheel head, but don't press down on
it. This is one of the first problems folks starting out throwing
have to deal with - they wonder how potters working for many years
can deal with all the pain on the sides of their hands ;-)
Bill
Ivor and Olive Lewis on wed 25 feb 04
Dear William Schran,
All the Aluminium oxide I have encountered has been white, except when
it was transparent and blue, red, green or yellow. But all the
aluminium oxide I have had in my hands that was black was highly
contaminated with Rutile.
So, why is Aluminium oxide from a wheel head black?
Ivor Lewis. Redhill, South Australia
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