iandol on fri 26 sep 03
Dear Diane Serley,=20
Adding a deflocculant introduces substances; Sodium Silicate, Sodium =
Phosphate, Sodium Carbonate or organic compounds (Darvan 7, Dispex) =
which have the ability to detach Calcium ions from clay and precipitate =
them as an insoluble materials. This affects clay/water structure by =
neutralising the strong effects of Calcium Ions on the polarity of the =
water molecules. The net result is to destroy a ordered water structure, =
(described in the popular "Water Hull" theory), so that it becomes a =
fluid again.
One way to think about it is to imagine the forces on clay particles are =
magnetic and water is like iron powder. With magnetism present the iron =
powder, which is not of itself magnetic, binds together as a solid =
aggregate. When the magnetism is removed, grains of iron powder do not =
attach themselves to their neighbours and are free to move =
independently. In the end it is all a question of changing the balance =
between the molecular forces which we choose to call "Bonds" that exist =
between similar and dissimilar substances.
I hope this assists you to achieve some degree of understanding.
Best regards,
Ivor Lewis. Redhill, South Australia.
Vince Pitelka on sat 27 sep 03
Ivor wrote:
"One way to think about it is to imagine the forces on clay particles are
magnetic and water is like iron powder. With magnetism present the iron
powder, which is not of itself magnetic, binds together as a solid
aggregate. When the magnetism is removed, grains of iron powder do not
attach themselves to their neighbours and are free to move independently. In
the end it is all a question of changing the balance between the molecular
forces which we choose to call "Bonds" that exist between similar and
dissimilar substances."
But Ivor, it sounds like you are talking about a flocculant, rather than a
deflocculant. The action of a deflocculant should be just the opposite,
right?
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Office - wpitelka@tntech.edu
615/597-6801 x111, FAX 615/597-6803
http://iweb.tntech.edu/wpitelka/
Maurice Weitman on sat 27 sep 03
At 5:13 PM +0930 on 9/26/03, iandol wrote:
>Adding a deflocculant introduces substances; Sodium Silicate, Sodium
>Phosphate, Sodium Carbonate or organic compounds (Darvan 7, Dispex)
>which have the ability to detach Calcium ions from clay and
>precipitate them as an insoluble materials. This affects clay/water
>structure by neutralising the strong effects of Calcium Ions on the
>polarity of the water molecules. The net result is to destroy a
>ordered water structure, (described in the popular "Water Hull"
>theory), so that it becomes a fluid again.
Thanks, Ivor, for the explanation.
Would you please explain, to expand to the molecular view of this you
provided, how, under what conditions, and whether magic water or
other deflocculants can be used to join clay of various states of
dryness?
I'd like to know whether it's possible, for instance, to join two
pieces of bone dry, or nearly so, clay, say in the case of a knob or
handle that gets knocked off while the piece is drying.
Or whether two pieces having dissimilar dryness (say one leather hard
or dryer, the other closer to bone dry) can be fused using magic
water.
And if it were possible, are there other tricks (waxing the piece and
its surrounding area) that need to be employed to enhance the bond
while it is forming and before it is fired?
Thanks.
Regards,
Maurice
Michael Wendt on sun 28 sep 03
Ivor wrote:
>. When the magnetism is removed, grains of iron powder do not
attach themselves to their neighbours and are free to move independently. In
the end it is all a question of changing the balance between the molecular
forces which we choose to call "Bonds" that exist between similar and
dissimilar substances.">
Reviewing the definition of a flock structure, I found his example to be
elegantly analogous. Clay in water normally agglomerates or forms clumps
called flock structures and deflocculants inhibit or break up those
structures.
Regards,
Michael Wendt
wendtpot@lewiston.com
Vince wrote:
>
But Ivor, it sounds like you are talking about a flocculant, rather than a
deflocculant. The action of a deflocculant should be just the opposite,
right?
>- Vince
Cindi Anderson on mon 29 sep 03
I use vinegar a lot and I feel that it works better with wet clay than very
dry clay. With two wet pieces, once you connect them with vinegar the only
way to get them apart is by cutting them apart (unlike slip which you can
slip around until it dries.)
I have had success joining dry to dry or wet to dry. I'll give an example I
just did last week. I had a piece that the bottom fell out of a year ago.
I finally had the same clay body back in my studio so I rolled a slab for
the bottom and let it almost dry (so it would shrink). Meanwhile I sprayed
the bottom of the pot a few times and covered in plastic, to try to get some
moisture into it. Then I made a mixture of clay and vinegar into a slip and
used it between the past leather hard bottom and the still very bone dry
top. I'm trying to remember if I scored... I don't think so because I have
found vinegar works best without scoring. If I did scoring it was very
light and because I had mixed clay with my vinegar as opposed to using
straight vinegar. I covered the outside joint with wet newspapers (didn't
have access to the inside or I would have done that too), then covered with
plastic, and let it sit. I have found this step very useful in attaching
parts of dissimilar moisture content. It gives a chance for the mosture on
both sides to even out. The fix appears very strong and had no difficulties
in firing.
Cindi
piedpotterhamelin@COMCAST.NET on mon 29 sep 03
Should I conclude from this that iron bearing clays are tighter with their
platelet arrangements and have a stronger magnetic attraction than white clays
and that is one reason why white clays are more "cream cheese" in feel due to
a reduced magnetic bonding of the platelets?
Rick
> Dear Vince,
> Absolutely correct, as I suggest in the second part of that paragraph.
> When you think about it, because Sodium Ions have only one valency bond, they
> effectively lock the clay away from the water.
> <<...With magnetism present the iron powder, which is not of itself magnetic,
> binds together as a solid aggregate. When the magnetism is removed, grains of
> iron powder do not attach themselves to their neighbours and are free to move
> independently...>>
> Do you think that makes sense. ? The Magnet and pure iron powder seems a pretty
> good analogy for flocculated clay and it is one I have not read of in the past.
> Best regards,
> Ivor Lewis. Redhill, South Australia
>
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