erosenth@eagle.liunet.edu on sun 30 jun 96
What is montmorillonite?
Is it a form of bentonite?
thank you,
Evan
erosenth@eagle.liunet.edu
Jun-ichi Inagaki on mon 1 jul 96
At 21:43 96/06/30 EDT, you wrote:
> ----------------------------Original message----------------------------
> What is montmorillonite?
>
> Is it a form of bentonite?
>
Montmorillonite is a clay minerals name.
Al2Si4O10(OH)2.xH2O
usualy incl. Mg ion.
It is much used in drilling muds, because of the gel-like suspension it
forms in water.
Bentonite is a rock consisting largely of montmorillonite.
///////////////////////////////////////
Jun-ichi INAGAKI
Mie Ceramic Research Institute / IGA branch
inagaki@mie-cri.yokkaichi.mie.jp
(TEL) +81-595-44-1019 / (FAX) 44-1043
Vince Pitelka on mon 1 jul 96
Evan -
Other way around - Bentonite is a Montmorillonite clay. The are several other
basic forms of clay, Kaolinite being the primary one. As far as I know, all of
the clays we use in ceramics, other than Bentonite, are variations of
Kaolinite.
- Vince
Vince Pitelka - wkp0067@tntech.edu
Appalachian Center for Crafts, Smithville, TN
Eric Lindgren on mon 1 jul 96
>Other way around - Bentonite is a Montmorillonite clay. The are several other
>basic forms of clay, Kaolinite being the primary one. As far as I know, all of
>the clays we use in ceramics, other than Bentonite, are variations of
>Kaolinite.
> - Vince
>Vince Pitelka - wkp0067@tntech.edu
>Appalachian Center for Crafts, Smithville, TN
When clay is formed from the parent rock, it can swing either way: to
kaolinite, or to montmorillonite (also known as smectite). Potter friend
Burt Cohen has dubbed it the evil clay - during his search for useful clays
in St. Lucia. A bit of montmorillonite is okay, but a lot is awful, causing
high shrinkage, warping and lots of cracking, and you can't clean it out of
the clay. Of course it has its appropriate uses, too.
Eric Lindgren
lindgren@muskoka.com
____________________
Dennis Whitfield on mon 1 jul 96
>----------------------------Original message----------------------------
>What is montmorillonite?
>
>Is it a form of bentonite?
>
>thank you,
>
>Evan
>erosenth@eagle.liunet.edu
>
>
Evan,
Bentonite is a clay - a clay will contains clay minerals with other earthy
materials (like feldspar) that are not clay. An important clay mineral in
bentonite is montmorillonite.
Montmorillonite is a clay mineral. Another clayart contributor has suggested
correctly that montmorillonite is not like kaolinite. Indeed, it has an
atomic structure more like mica than like kaolinite.
Montmorillonite is a member of a group of clay minerals that are
collectively known as smectites.
Montmorillonite is a common constituant of sediments and consists of VERY
fine plate -like particles less than 0.05 microns in diameter. This means
that even with electron microscopes , it is difficult to see the individual
particles.
Montmorillonitic clays are generally very fat and plastic, with high drying
shrinkages and with good green and dry strengths. They tend to reduce the
vitrification range of bodies to which they are added and increases the
coefficient of thermal expansion.
Regards
Denis
****************************************************************************
DR DENIS WHITFIELD
Senior Lecturer
Co Director, Centre for Ceramic Research, Design and Production
Department of Visual and Peforming Arts
University of Western Sydney, Macarthur
PO Box 555
CAMPBELLTOWN NSW 2560
AUSTRALIA
email: d.whitfield@uws.edu.au
phone: 02 7729345
****************************************************************************
Craig Martell on fri 26 feb 99
Hi:
I first heard about montmorillonite from Harry Davis, many moons past. One
of Harry's criteria for suspecting a clay to have a montmorillonitic, and
not a true kaolin lattice was the drying property of the clay. Harry
maintained that montmorillonites don't have the "capillary" action that
kaolins do and hence will not pass water from wetter to dryer areas in any
given pot form. So, if you have a clay that shows areas of bone dryness and
is still wet in the bottom, or other areas, this may be a claybody with
significant montmorillonite content. One clay that I tried which seemed to
really fit this criteria was B mix. Nice throwing clay but hell-on-wheels
when it comes to managing the drying.
later, Craig Martell in Oregon
Vince Pitelka on sat 27 feb 99
>I first heard about montmorillonite from Harry Davis, many moons past. One
>of Harry's criteria for suspecting a clay to have a montmorillonitic, and
>not a true kaolin lattice was the drying property of the clay. Harry
>maintained that montmorillonites don't have the "capillary" action that
>kaolins do and hence will not pass water from wetter to dryer areas in any
>given pot form.
Craig -
This is exactly right. The montmorillonitic clays are so fine that they
essentally clog the pores in the claybody, just as they clog the pores in
the soil in an agricultural holding pond. When you need to boost
plasticity, bentonite is wonderful in very small doses, but in larger
amounts it becomes very destructive.
- Vince
Vince Pitelka - vpitelka@DeKalb.net
Home 615/597-5376, work 615/597-6801, fax 615/597-6803
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
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