jean mitton on mon 23 jul 01
Dear Clayarters,
=20
Vince's observations that there is a big difference =
between the definition of Burnishing and polishing, I feel is debatable. =
But the use of a hard versus soft object to do this with, certainly =
makes a difference.
But be that as it may, the word "Polish" has prompted this post, =
and therefore the heading and some discussion on "Ball Mills"
As someone who is interested in constructing a ball mill, I was =
lead by the archives to a D.I.Y. ball mill made originally from a design =
by Cardew's "Pioneer Pottery". This was modified and admirably described =
and illustrated by John Harlow on his website =
http://www.bath.ac.uk/~ccsjrh/ballmill.htm
However as John himself states in his description that he has had =
little wear on the plastic drum in 20 years.... I feel that this is a =
polishing mill and not ideal or efficient for grinding material. I say =
this having had some experience with Industrial Ball Mills in the mining =
Industry.
These all have liners generally with a wave pattern on the wearing =
face(Inside diameter) and as the wave wears down the efficiency of the =
mill lessons considerably.
What are the opinions of interested experienced Ball Millers, Potters =
and Vince, of course.
,
Ron Mitton.=20
South Africa.
vince pitelka on tue 24 jul 01
Ron Mitten wrote:
"These all have liners generally with a wave pattern on the wearing
face(Inside diameter) and as the wave wears down the efficiency of the mill
lessons considerably. What are the opinions of interested experienced Ball
Millers, Potters and Vince, of course."
Ron -
I think you are mistaking what we normally think of as a ball mill in
ceramics, and the large industrial ball mills which are used for grinding
minerals. With the small ball mills we use, the degree of grinding or
polishing depends on the media you use in the mill along with the material
to be ground or polished, and has nothing to do with patterns on the inner
surface of the mill drum or vessel. The drum or vessel is usually either
porcelain, or else metal lined with rubber or plastic.
You can put a load of colored porcelain beads in a ball mill along with the
right sequence of polishing grit, and attain an overall high-gloss finish
with no glaze. Or you can load the ball mill with a charge of flint pebbles
or porcelain marbles along with your terra sig and Mason stains, and reduce
the particle size by the grinding action of the pebbles or marbles.
And since you prefaced your message by referencing my definitions of
burnishing and polishing, I am afraid I am only familiar with the
definitions used in the United States, and I appologize if they do not
conform to your understanding of those terms. Over here, burnishing
involves compressing a surface with a hard shiny object. It may be
considered a form of polishing. But you can also polish by rubbing a
slightly damp clay or slip (preferably terra sigillata) surface with a piece
of chamois, a soft brush or cloth, or a flexible piece of plastic sheeting.
That is polishing, but should not be referred to as burnishing.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://www.craftcenter.tntech.edu/
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