David Woof on sun 4 apr 10
=3D20
=3D20
Vince wrote: =3D
y to blame thixotropy......> (see below)
=3D20
David says: I have to weigh in with Vince on this. I think he has covered t=
=3D
he hard to slammed softened clay question=3D2C so now let's move on to the =
ot=3D
her largely unrelated topic of thixotropic phenomenon.
=3D20
James with respect=3D2C let's put your hypothesis up to the test of chemica=
l/=3D
physical fact.=3D20
=3D20
Ivor cites gels in reference to thixotropic properties of a material. Yes=
=3D
=3D2C but there is more=3D2C and one might pause to ask=3D3B when is the ba=
gged c=3D
lay the original poster of this thread was asking about slamming on the flo=
=3D
or ever considered a gel?=3D20
=3D20
A true workable thixotropic condition in clay is established by the additio=
=3D
n of enough potassium=3D2C lithium=3D2C or sodium elements to cause changes=
in =3D
the attraction between the positively and negatively charged ions in the cl=
=3D
ay body.
=3D20
If you consider recipes for thixotropic clay bodies you will note that they=
=3D
contain combinations of soda feldspar or Nepheline syenite=3D2C rather tha=
n =3D
Custer=3D2C and a low alumina=3D2C sodium borosilicate frit like ferro 3124=
.
=3D20
Quite unusual for a typical potter's clay body formulation.
=3D20
Whip up a batch=3D2C interesting stuff!!! You can't throw with it but if ji=
gg=3D
led=3D2C pulled=3D2C twisted and draped over other clay forms or a hump mol=
d it=3D
can be a very fascinating material.
=3D20
David Woof
=3D20
________________________________________________________________________-
=3D20
Re: bag of clay seem hard/then smashed on floor=3D2C seem softer?Posted by:=
"=3D
Vince Pitelka" vpitelka@DTCCOM.NET Date: Fri Apr 2=3D2C 2010 7:53 pm ((PDT)=
)=3D
=3D20
=3D20
Ivor Lewis wrote:"Your Clay is Thixotropic. Per OED=3D2C "The property disp=
la=3D
yed by certain gelsof becoming fluid when shaken=3D2C stirred=3D2C etc.=3D2=
C and =3D
of reverting back to a gelwhen left to stand=3D3B reduction of viscosity in=
t=3D
he presence of an appliedstress. A quality exhibited by compounded clay bod=
=3D
ies in whichMontmorillonite(Bentonite)is a component."=3D20
=3D20
Ivor -I am a little baffled as to why so many people are ready to blamethix=
=3D
otropy. This does happen=3D2C of course=3D2C but it is rarely what is happe=
ning=3D
when clay that has been sitting for a while seems stiff=3D2C but becomes pl=
as=3D
ticafter being dropped on the floor once or twice. The key word here is"pla=
=3D
stic." Roxanne did not say that her clay turned to jelly - just that itbeca=
=3D
me plastic=3D2C and that is not thixotropic clay. I know I already wrote ap=
os=3D
t about this=3D2C but I am being redundant because I want people toundersta=
nd=3D
what is happening. In most cases=3D2C when you drop a stiff bag ofclay on =
th=3D
e floor and it becomes softer=3D2C it is just a case ofre-establishing the =
wa=3D
ter layers between the platelets=3D2C thus restoringplasticity. It's that d=
el=3D
icate balance of lubrication and friction thatever potter knows intuitively=
=3D
.- Vince =3D20
_________________________________________________________________
Hotmail has tools for the New Busy. Search=3D2C chat and e-mail from your i=
nb=3D
ox.
http://www.windowslive.com/campaign/thenewbusy?ocid=3D3DPID28326::T:WLMTAGL=
:O=3D
N:WL:en-US:WM_HMP:042010_1=3D
ivor & olive lewis on mon 5 apr 10
"Ivor cites gels in reference to thixotropic properties of a material"
Dear David Woof,
Did I....?.
I thought I had only considered the distinction between Kaolinite minerals
and Montmorilonite minerals.
Glen C. Nelson covers Thixotropic clay. His remark is that the clay is
deflocculated by the presence of Alkali metal elements, confirming your
suggestion. But his recipe gives no other clues. Perhaps you would like to
provide more examples of thixotropic clay compositions with specific
information about the mineral content of each clay fraction . Montmorilonit=
e
(Bentonite) clay is remarkable in its ability to sequester both Water and
cations (eg Na and K)
All the best,
Ivor Lewis,
Redhill,
South Australia
David Woof on tue 6 apr 10
Ivor=3D2C
My interest in participating with this group is to glean=3D2C garner=3D2C a=
nd s=3D
hare information that has practical application in our everyday studio prac=
=3D
tice and teaching.
=3D20
Though I appreciate that some post to this group the science and technical =
=3D
information that can educate and form a firm background of understanding=3D=
2C=3D
my mission is to break this down to terms both practical and accessable to=
=3D
the "great unwashed" picking scraps and leavings at the base of the Ivory =
=3D
Towers some folks imagine that they inhabit.
=3D20
I have no inclination <"to provide more examples of thixotropic clay compos=
=3D
itions with specific information about the mineral content of each clay fra=
=3D
ction."> nor time I wish to spend on ego driven academic huffing=3D2C puffi=
ng=3D
and chest beating.
=3D20
My mission in responding to this thread was to redirect it to a more produc=
=3D
tive discussion as related to potters clay bodies=3D2C thixotropic and othe=
rw=3D
ise. You guys went for it!!!
=3D20
Mission accomplished! Woof is moving on=3D2C leaving best regards to all.
=3D20
___________________________________________________________________________=
=3D
_____________________________________________________________________11a. T=
=3D
hixotropic clay? smash bag on floor etc. James=3D2C Ivor=3D2C Vince=3D2C Al=
lPoste=3D
d by: "ivor & olive lewis" iandol@WESTNET.COM.AU Date: Mon Apr 5=3D2C 2010 =
9:=3D
54 am ((PDT))=3D20
=3D20
"Ivor cites gels in reference to thixotropic properties of a material"
=3D20
Dear David Woof=3D2CDid I....?.I thought I had only considered the distinct=
io=3D
n between Kaolinite mineralsand Montmorilonite minerals.Glen C. Nelson cove=
=3D
rs Thixotropic clay. His remark is that the clay isdeflocculated by the pre=
=3D
sence of Alkali metal elements=3D2C confirming yoursuggestion. But his reci=
pe=3D
gives no other clues. Perhaps you would like toprovide more examples of th=
=3D
ixotropic clay compositions with specificinformation about the mineral cont=
=3D
ent of each clay fraction . Montmorilonite(Bentonite) clay is remarkable in=
=3D
its ability to sequester both Water andcations (eg Na and K)All the best=
=3D
=3D2CIvor Lewis=3D2CRedhill=3D2CSouth Australia =
=3D20
_________________________________________________________________
The New Busy is not the old busy. Search=3D2C chat and e-mail from your inb=
ox=3D
.
http://www.windowslive.com/campaign/thenewbusy?ocid=3D3DPID28326::T:WLMTAGL=
:O=3D
N:WL:en-US:WM_HMP:042010_3=3D
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