Carol Tripp on fri 27 jan 06
Picture this; it's a new term at the Dubai Int'l Art Centre and we have new
clay to use on the wheel. It's Oxidizing St Thomas, an iron bearing, ^9
clay with grog in it, from Potclays UK. It's sold as being good for
throwing. I drop the bag on the floor four or five times to soften it up.
Then I wedge a kilo - noticing some cracking but trying to ignore it. ( I've
worked with shortish clay before.) Then I sit at the wheel to do a demo for
my class. I cone it several times until it feels right and everyone has had
a chance to see how coning is done. Then I pull up the wall once. Hum, the
rim is rather uneven. Pull up again - uh-oh, it's like cordoroy. I try to
consolidate the rim and about an inch down to get rid of the 'bumps', pull
up again and the rim gets worse - the bumps are actually cracks that run
down into the walls. Ok, let's stretch the rim outwards and,... the pots
breaks apart. It doesn't slump, it breaks. Take a piece of clay and roll
it into a coil, twist it and it breaks before the first twist is done. This
clay is seriously short. And furthermore, when someone does manage to throw
a pot with it, glaze it and fire it - it bloats! Great stuff.
I sent an email of complaint to the supplier, Potclays, and they responded
with a rather snide email about how no one else has complained about this
clay. (So that implies we are idiots on our own?) That the warmer weather
must have dried it out (so, plasticity is just a function of wetness? then
explain to me about the two year old hardish Tuckers I wrestled with
yesterday in my studio, no lack of plasticity there...) and that I didn't
wedge the clay before using it "a techique taught in every school in the Uk"
or words to that effect. Oh, so I don't know about wedging. What? !??
(Tell me, just how does wedging the clay make it any less short?) As you
may be able to tell, their response goes right up my nose. And they didn't
even address the bloating issue.
So, the Art Centre has 1500kg of clay that Potclays is probably going to
stonewall us on. We'll be sending them a sample of the bad clay but I don't
hold out much hope of any recompense. Personally, I would never buy another
thing from them but I am not the decision maker. I am already working on
something; I've wedged some of it half and half with another clay that the
hand-building classes us (also from Potclays) and that mixturewas ok to
throw. These experiment pots need bisquing, glazing and firing and then
we'll see if it bloats.
Thanks for listening. I just really needed to blow off some steam.
Moral of the story - BUY CLAY FROM A COMPANY THAT TESTS ITS CLAYS BEFORE IT
SHIPS THEM.
Best regards,
Carol
Dubai, UAE
Where I am so glad that I have my own studio, tiny as it is, buy my own
clay, glaze chemicals, make my own glazes, and fire my own kiln. Control.
;-P
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Kathi LeSueur on fri 27 jan 06
Carol Tripp wrote:
> .....Take a piece of clay and roll
> it into a coil, twist it and it breaks before the first twist is
> done. This
> clay is seriously short. And furthermore, when someone does manage to
> throw
> a pot with it, glaze it and fire it - it bloats! Great stuff.
>
> I sent an email of complaint to the supplier, Potclays, and they responded
> with a rather snide email about how no one else has complained about this
> clay......>>
Many years ago I bought clay from a supplier who had a sign that said,
"Tis a poor potter who blames his clay." After awhile I decided it was
just an excuse for when he made a batch of lousy clay. Haven't bought
from him in years.
Kathi
Michael Wendt on fri 27 jan 06
Ah ;-)
You have hit on a key theme I stress with all students I teach to throw.
The clay matters!
Try different clays from different suppliers. Dry the pieces under various
sets of conditions.
Fire enough pieces to learn the ins and outs of a clay before you commit to
it for production work.
Buy enough at a time to be sure you can do a large order without running out
and order and test more long before you need it so that variations the occur
can be detected before disaster hits.The clay you choose must be the usual
things like the correct cone and firing character as well as a good forming
material with low loss rates.
Then the potter must do his job and get the clay ready to throw. Either a
good pug mill or careful wedging are a must. Clay that has been stored for a
while no longer is uniform in moisture due to condensation on the inside of
the bag.
Never skimp. When you find a good supplier, support him and tell others so
that good clay continues to be available. Too often, people want to save a
nickel a pound.
On a $15.00 item that requires a pound of clay, why quibble about a nickel?
That is a false economy if one clay works better than another.
The clay matters!
Regards,
Too often I see potters take clay right from the bag, plop it onto the
wheel, try to throw and then blame the clay when the pot comes out all
goofy.
Michael Wendt
Wendt Pottery
2729 Clearwater Ave
Lewiston, Idaho 83501
USA
wendtpot@lewiston.com
www.wendtpottery.com
Ivor and Olive Lewis on sat 28 jan 06
Dear Carol Tripp,=20
It is not unusual for "Factory Made Clay" to be a bit short. Perhaps =
they kept it in the filter press for an extended time before putting it =
through the pug mill.
Almost fifty years ago when I first tried my hand at the wheel ( =
homemade ) I got my clay via an agent in the city where I lived. I =
bought a hundredweight. It was delivered in a wooden packing case as =
four rather hefty "Two Stone" blocks. Although I did make a few rather =
small items it was some years later that I realised that I should have =
added water to it and worked it into a good plastic condition. Later, I =
learned how to do the "bend a roll of clay over your finger test" to =
find out if the clay I was preparing or buying was short or long.
A ton of bad clay, yes, been there, done that ! ! Got one that was a =
persistent "Cracker"
Best regards,
Ivor
Ron Roy on sun 29 jan 06
Hi Carol,
I can offer a possible solution to the lack of plasticity but not the bloating.
Adding 0.2% of disolved Epsom salts may be just what you need - if you have
a pug mill or some way of adding it in - try a small amount.
Easy to test a handful with a few drops of disolved salts.
2 lb. of Epsom salts in 1000 lb. of dry clay - so that is .2 lb. in 100 lb
dry - which works out to about 140 lb. of wet clay.
Just make sure the Epsom is completely disolved - I would use a microwave
to do it.
I can only agree with the advice to buy your clay from a company that tests
their product - it's not hard to find them - just ask for the data on the
last years production. If they have done it - and the results show they
are doing their job - they will be happy to send you the results.
RR
>So, the Art Centre has 1500kg of clay that Potclays is probably going to
>stonewall us on. We'll be sending them a sample of the bad clay but I don't
>hold out much hope of any recompense. Personally, I would never buy another
>thing from them but I am not the decision maker. I am already working on
>something; I've wedged some of it half and half with another clay that the
>hand-building classes us (also from Potclays) and that mixturewas ok to
>throw. These experiment pots need bisquing, glazing and firing and then
>we'll see if it bloats.
>
>Thanks for listening. I just really needed to blow off some steam.
>
>Moral of the story - BUY CLAY FROM A COMPANY THAT TESTS ITS CLAYS BEFORE IT
>SHIPS THEM.
>
>Best regards,
>Carol
>Dubai, UAE
>Where I am so glad that I have my own studio, tiny as it is, buy my own
>clay, glaze chemicals, make my own glazes, and fire my own kiln. Control.
>;-P
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ron Roy on sun 29 jan 06
I must endorse what Michael is saying here - especially about testing any
clay you make or buy - knowing a few simple things about the clay you use
is invaluable - especially when trying to deal with bad clay from a
supplier.
It only takes a few minutes to grab a little clay from a new shipment and
make a couple of bars to test for shrinkage and absorbency.
Take that a step further and mix your glazes before you need them and test
to see if they are right.
RR
>You have hit on a key theme I stress with all students I teach to throw.
>The clay matters!
>Try different clays from different suppliers. Dry the pieces under various
>sets of conditions.
>Fire enough pieces to learn the ins and outs of a clay before you commit to
>it for production work.
>Buy enough at a time to be sure you can do a large order without running out
>and order and test more long before you need it so that variations the occur
>can be detected before disaster hits.The clay you choose must be the usual
>things like the correct cone and firing character as well as a good forming
>material with low loss rates.
>Then the potter must do his job and get the clay ready to throw. Either a
>good pug mill or careful wedging are a must. Clay that has been stored for a
>while no longer is uniform in moisture due to condensation on the inside of
>the bag.
>Never skimp. When you find a good supplier, support him and tell others so
>that good clay continues to be available. Too often, people want to save a
>nickel a pound.
>On a $15.00 item that requires a pound of clay, why quibble about a nickel?
>That is a false economy if one clay works better than another.
>The clay matters!
>Regards,
>Too often I see potters take clay right from the bag, plop it onto the
>wheel, try to throw and then blame the clay when the pot comes out all
>goofy.
>Michael Wendt
>Wendt Pottery
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
boobyagga@juno.com on mon 30 jan 06
ivor, and everyone else, whats this "bend and roll" techinque over your =
fingers for plasticity?? never heard of it. would definately like to kno=
w. on a similar note...i think i destroyed 100 lbs of clay...and i dont =
know why or how.
i havent thrown anything in about 3 days...so last night i went out to m=
y studio to throw. made a ball about 4 lbs....went to throw it and it ea=
sily ripped. something ive NEVER had happen before. so i went back to my=
clay barrel and took another ball...and i could easily rip it in my han=
ds...no stretching...no nothign...just a good easy rip in half. and its =
rather wet clay. more wet than i normally throw with. and when examining=
the rip...it ripped in a thousand tiny layers. right along the platlets=
formed when wedging. now i have added nothing to this clay since the la=
st time i threw. ive been doing some vinegar experiments...but that clay=
has not come in contact with this clay...ive kept it rather separate. t=
he only possible is maybe a few drops of slip with vinegar from my hands=
. and this clay was perfect for throwing the last time i threw...no prob=
lems. now i cant for anything without it ripping apart in great spirals =
around and upwards. kinda confused. i wouldnt think bacteria or anything=
could form that quickly in such a cool enviroment and destroy the clay.=
..so i doubt its that. and i dont even own any deflocculants...so it can=
t be that. vinegar is a slight flocculant...but it hasnt come in any sig=
nificant contact.....
im taking a small portion and drying it out completely and slaking it ou=
t with pure water and we will see how that works out. =
oh yeah and it smells pretty good actually. the smell is definately not =
the rotting earthy smell im used to in the clay buckets. =
really im not that worried...its only 100lbs of clay...nothing to fret o=
ver...im just wondering why the heck it happend. its mostly useless for =
anything. i wouldnt trust it now for hand building either. odd.
thanks guys.
oh yeah...and can i distill/evaporate 5% acidity vinegar to increase the=
acidity??
thanks, jason
Steve Slatin on mon 30 jan 06
Jason --
I can't help with the clay, but yes, you can concentrate acetic
acid (vinegar) and no, you probably shouldn't.
You can because it's got a higher boiling point than water, about
118 C. This is not so greatly different from water, though, so
you can't just boil off the water and leave the acetic acid behind.
You'll have to do a proper cool-and-condense number on it,
and then acetic acid is available in high concentration. This
only gets you so far, though, IIRC, on account of acetic
acid's hydrophilic nature. It'd take a very carefully controlled
distillation to get something fairly pure, at which point the
DEA will probably be breaking down your door hoping to have
found a meth lab or something.
But you may not want highly concentrated acetic acid in you
workshop anyway, as it's quite the irritant (fumes will
leave your nose burning for hours, and glacial acetic acid
will burn the skin right off you). If you really need to get
there -- have highly concentrated acetic acid -- you'd
probably be better off going with sodium hydroxide and
baking soda to get sodium acetate as a solid then
reacting the sodium acetate with a powerful acid (sulfuric
or the like) to get glacial acetic acid.*
Acetic acid is so very hydrophilic that for centuries folks
thought it was different from vinegar. Note how many folks
here practically bathe in the stuff with no ill effect?** Weak
solutions of acetic acid are a miracle ... "and miracles are
the way things ought to be."***
Best wishes -- Steve Slatin
*(My wife is taking a chemistry class. Could you tell?)
**(Do not pursue this, however, or Kelly S. will probably
jump in with something that will give you the willies.)
***Cyrus, from "The Warriors", right before his assassination.
"boobyagga@juno.com" wrote:
ivor, and everyone else, whats this "bend and roll" techinque over your fingers
oh yeah...and can i distill/evaporate 5% acidity vinegar to increase the acidity??
thanks, jason
Steve Slatin --
In watermelon sugar the deeds were done and done again
as my life is done in watermelon sugar.
---------------------------------
What are the most popular cars? Find out at Yahoo! Autos
Taylor, in Rockport TX on mon 30 jan 06
On Mon, 30 Jan 2006 18:07:34 GMT, boobyagga@juno.com
wrote:
>ivor, and everyone else, whats this "bend and roll" techinque over your
fingers for plasticity?? never heard of it. would definately like to know.
Jason, roll out a short snake of clay, maybe a little thicker than a
standard pencil. Now wrap it around one of your index fingers. Plastic
clay will bend around the finger with little to no cracking. Nonplastic
clay will break in two. Much territory betwixt the extremes. My local
clay is quite sandy and does not survive the finger test. Super short.
The ripping balls of clay is odd indeed. Hope you find a solution. Sounds
like you're pulling out pre made clay balls. I can never get away with
that. If I prepare measures of clay and I don't use them pretty soon. I
must rewedge and prepare or there is hell to pay at the wheel. I've not
been throwing long.
Taylor in Rockport, TX
Chris Schafale on mon 30 jan 06
Any chance the clay got frozen in the meantime?
At 01:07 PM 01/30/2006, you wrote:
>ivor, and everyone else, whats this "bend and roll" techinque over your
>fingers for plasticity?? never heard of it. would definately like to know.
>on a similar note...i think i destroyed 100 lbs of clay...and i dont know
>why or how.
>i havent thrown anything in about 3 days...so last night i went out to my
>studio to throw. made a ball about 4 lbs....went to throw it and it easily
>ripped. something ive NEVER had happen before. so i went back to my clay
>barrel and took another ball...
dewitt on mon 30 jan 06
> oh yeah...and can i distill/evaporate 5% acidity vinegar to increase the =
acidity??
Probably easier, you can buy horticultural vinegar. It's on the order of 20=
%.
deg
Ivor and Olive Lewis on tue 31 jan 06
Dear Jason,
That shortness test is quite simple. Take a chunk of clay, just a =
handful. Squeeze it into a sausage and then roll it in your palm to get =
is smooth and uniform in diameter, about the thickness of your =
forefinger. Now hold it firm between fore and middle finger and with =
your other hand bend it around and down beside your thumb. A good =
plastic clay ready to throw should bend without showing any signs of =
fissuring. Slight fissuring may mean it needs more water incorporating. =
But if it cracks then it is a short clay.
What to do with a short clay. Let it dry out, bone dry. Rough crush then =
cover with water, add about ten percent of a good ball clay, blunge. =
Allow to soak for a couple of weeks, blunging ever couple of days. =
De-water and wedge. Let it rest, wedge and then use. Which reminds me, I =
have clay to reclaim.
Sounds as though your clay is short of water and needs some ball clay. =
You are not seeing platelets. They are an enormous one thousandth of a =
millimetre across. That is "Flock Structure". (Don't ask " How do you =
know". Believe me)
Best regards,
Ivor
Steve Slatin on tue 31 jan 06
Jason --
Just curious -- why are you trying to dissolve your oxides?
-- Steve Slatin
"boobyagga@juno.com" wrote: hahahaha no sorry guys i am not starting my very own baby meth lab :-) i just want something along the lines of 10-20%....all i can find from grocery stores is 5%...and that takes FOREVER to disolve any ammount of oxides in
Steve Slatin --
In watermelon sugar the deeds were done and done again
as my life is done in watermelon sugar.
---------------------------------
Do you Yahoo!?
With a free 1 GB, there's more in store with Yahoo! Mail.
boobyagga@juno.com on wed 1 feb 06
hahahaha no sorry guys i am not starting my very own baby meth lab :-) i=
just want something along the lines of 10-20%....all i can find from gr=
ocery stores is 5%...and that takes FOREVER to disolve any ammount of ox=
ides in and requires an exorbitant ammount. im not looking for pure hard=
core acetic acid. that would be like playing with pure clorine bleach...=
.which is definately not fun.
and no my clay didnt freeze. lately the temperatures have been an incred=
ibly hot 75 degrees down here in texas...we havent seen a freeze in quit=
e a while. however...last night did dip down to 38 degrees...with my win=
dows open in my bedroom...i woke up very very cold. =
still no real idea as to what happened to my clay. the stuff i dried out=
and added pure water too seems to be alright....except its still quite =
wet so its hard to tell if the plasticity is back or if its just the wat=
er. =
still confused. but oh well.
jason.
Lee Love on thu 2 feb 06
Steve Slatin wrote:
>"boobyagga@juno.com" wrote: hahahaha no sorry guys i am not starting my very own baby meth lab :-) i just want something along the lines of 10-20%....all i can find from grocery stores is 5%...and that takes FOREVER to disolve any ammount of oxides in
>
>
Lemon juice is more acidic than vinegar.
--
Lee Love
in Mashiko, Japan http://mashiko.org
http://seisokuro.blogspot.com/ My Photo Logs
http://ikiru.blogspot.com/ Zen and Craft
"The way we are, we are members of each other. All of us. Everything.
The difference ain't in who is a member and who is not, but in who knows
it and who don't."
--Burley Coulter (Wendell Berry)
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