vince pitelka on tue 9 jul 02
> Ive been advised to deffloculate the slurry when preparing the clay. As i
> use it basically for throwing on the wheel I wonder if its a good idea.
The
> suggestion is in order to use less water and spend less time drying .He
also
> says that once the slurry is in paste the deffloculants are no more active
> as the ionic attraction is no longer working. What do you say???
Jorge -
This is a bad idea. You never want to introduce a deflocculant to a
throwing or handbuilding body, because it makes the particles repel one
another, and will decrease plasticity. On the contrary, it is a very good
idea to add a little vinegar when stiffening recycle and mixing claybodies.
It makes the clay stickier, and hastens the formation of organic activity,
which further increases the plasticity.
Good luck -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@worldnet.att.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://www.craftcenter.tntech.edu/
Jorge Nabel on tue 9 jul 02
Ive been advised to deffloculate the slurry when preparing the clay. As i
use it basically for throwing on the wheel I wonder if its a good idea. The
suggestion is in order to use less water and spend less time drying .He also
says that once the slurry is in paste the deffloculants are no more active
as the ionic attraction is no longer working. What do you say???
Jorge Nabel en Buenos Aires, very very cold, 1 Celsius, and so painfull when
throwing.
Longtin, Jeff on wed 10 jul 02
Jorge,
Often times at the end of a casting session I'll take the accumulated scraps
and roll them into a ball. I'll often roll this clay out for glaze test
pieces and/or new texture experiments. The clay seems to "skin" really
easily. This skin does not smooth out easily. (You've seen pictures of soil
in the dessert, all cracked on the surface, that's what this "skin" looks
like.)
Deflocculated clay rolled out also has an exceddingly flimsy quality. (Kinda
like a crepe just after cooking.)It doesn't have the same strength as non
deflocculated clay. You can wait for it to set up some but still it doesn't
seem to take a shape as soon.
Just a note: deflucculation allows you reduce your water content to the same
as solid (non-deflocculated) clay. As such I'm not quite sure its exactly
the same, in a solid state, as solid clay. Undeflocculated you would need
about 50% water to make clay liquid, deflocculated you just need about 35%
or so (solid clay btw is about 35% water). If you're using deflocculated
clay in a more solid state I would imagine you have a clay with even less
water than the original 35% it had in the begining so I'm not sure you can
say the two clays are similar at that point?
As I have throwing clay in the studio as well I haven't experimented with
throwing casting clay so my comments may be of little use.
Good Luck in any case
Jeff Longtin
-----Original Message-----
From: Jorge Nabel [mailto:alfareriaurbana@SION.COM]
Sent: Tuesday, July 09, 2002 7:44 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: deffloculating for throwing
Ive been advised to deffloculate the slurry when preparing the clay. As i
use it basically for throwing on the wheel I wonder if its a good idea. The
suggestion is in order to use less water and spend less time drying .He also
says that once the slurry is in paste the deffloculants are no more active
as the ionic attraction is no longer working. What do you say???
Jorge Nabel en Buenos Aires, very very cold, 1 Celsius, and so painfull when
throwing.
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Ababi on thu 11 jul 02
Hi!
I add deflocculant to paperclay in order to have faster drying on the plaster boards.
I thought to myself. If I have paper inside that helps me to work with the clay, might
help me with the plasticity. I made a paperclay with my unplastic English kaolin lower
in cost. It was hard to work with.
Another test I made: Prepare the paperclay without deflocculant, took much longer to
dry.
Ababi Sharon
Glaze addict
Kibbutz Shoval Israel
ababisha@shoval.org.il
http://members4.clubphoto.com/ababi306910/
Ababi on thu 11 jul 02
An add: I do handbuilding
Ababi
Michael Banks on thu 11 jul 02
Jorge, This is completely wrong advice. Deflocculating a clay (usually
with a soluble sodium compound) is difficult to reverse, except by intensive
washing out the soluble sodium ions with copious water. Which is the
opposite of what you're trying to achieve.
Even adding a lot of flocculant will not redress plastic deflocculated clay
to a workable state. The clay remains flabby and thixotropic and difficult,
or impossible to throw successfully. This is because (without washing) the
sodium cations (positively charged) remain in the clay, in close proximity
to the negatively charged faces of the clay grains. Adding flocculants only
results in a compromised attraction & repulsion force which manifests as
strong thixotropic behaviour. This is the tendency to flow in response to
weak mechanical forces (or conversely, stiffen on remaining undisturbed).
This is the antithesis of that required for wheel work or handbuilding.
Michael Banks,
Nelson
NZ
----- Original Message -----
Jorge Nabel Wrote:
> Ive been advised to deffloculate the slurry when preparing the clay. As i
> use it basically for throwing on the wheel I wonder if its a good idea.
The
> suggestion is in order to use less water and spend less time drying .He
also
> says that once the slurry is in paste the deffloculants are no more active
> as the ionic attraction is no longer working. What do you say???
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