Ivor and Olive Lewis on tue 21 feb 06
AS I understand the science of these materials, though they have the =
same elemental composition they have every different crystal lattice =
structures, and hence very different crystal shapes.
One consequence of this is that Halloysite clay crystals roll into a =
cylindrical shape when they loose water of plasticity. This causes =
excessive shrinking in comparison to the same degree of water loss from =
a Kaolinite/water mixture.=20
K. Norrish reported to the "Clay Controlling the Environment Conference" =
in 1993 about a fibrous Halloysite which had a tubular crystal. (p275-7)
McKee, Dixon, Whitethouse and Harling published a paper in 1973, "Study =
of Te Puke Halloysite by high resolution Electron Microscope."
These may be leads worth following. I think a search of Chemical =
Abstracts would be more rewarding than Google or Yahoo.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Michael Wendt on wed 22 feb 06
The local geologist for i-minerals group, Phil Nisbet, shared some insights
into why Helmer Kaolin is so plastic.
First, it is sedimentary at the end of a very long lake structure so that
all the large material settled out long before it got to Helmer.
Second, it is not all one clay but a natural blend which contains a peculiar
mineral he calls 4 water halloysite which is spheriodal and super white. It
also contains tubular Halloysite and a bentonite. The majority of the clay
is Kaolinite but very much milled by nature during transport so that the
SEMs of the platelets I saw had rather rough edges to them.
I suspect that the variety of sizes from fine to superfine with a small
amount of coarse accounts for the high shrinkage and plasticity.
Any of you coming to Portland who use porcelain, I will bring small samples
of the Helmer cone 10 body we use as well as our DR-10 drag reducing agent
and the new High Alumina bottom wax that does not settle during use (making
brushing easier and more convenient).
Regards,
Michael Wendt
Wendt Pottery
2729 Clearwater Ave
Lewiston, Idaho 83501
USA
wendtpot@lewiston.com
www.wendtpottery.com
David Beumee on thu 23 feb 06
Most interesting Ivor! Strange then that Ajax, Helmer, EPK, and Super Standard kaolins all had similar or greater shrinkage rates as Ultrafine H (Halloysite) from NZ. Most sorry indeed to have missed this discussion!
David Beumee
-------------- Original message ----------------------
From: Ivor and Olive Lewis
> AS I understand the science of these materials, though they have the same
> elemental composition they have every different crystal lattice structures, and
> hence very different crystal shapes.
> One consequence of this is that Halloysite clay crystals roll into a cylindrical
> shape when they loose water of plasticity. This causes excessive shrinking in
> comparison to the same degree of water loss from a Kaolinite/water mixture.
> K. Norrish reported to the "Clay Controlling the Environment Conference" in 1993
> about a fibrous Halloysite which had a tubular crystal. (p275-7)
> McKee, Dixon, Whitethouse and Harling published a paper in 1973, "Study of Te
> Puke Halloysite by high resolution Electron Microscope."
> These may be leads worth following. I think a search of Chemical Abstracts would
> be more rewarding than Google or Yahoo.
> Best regards,
> Ivor Lewis.
> Redhill,
> South Australia.
>
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