Cathy Nelson Hartman on sat 6 apr 96
I am currently using this porcelain clay body:
EPK 25
OM 4 25
Minspar 25
Silica 25
+ 1-2 % bentonite
The body doesn't lend itself to throwing large round shapes which I would
like to do. I am interested in any suggestions as to possible additions
to my body that would improve its ability to stand up during the throwing
process. I am aware of using torches to stiffen the pot. Also, I don't
want to add any ingredients that will introduce iron because I am using
pastel glazes on a white background.
A single ingredient solution would be the best of all possible answers.
Anybody out there have a suggestion?
walter hartman
Ron Roy on sun 7 apr 96
>----------------------------Original message----------------------------
>I am currently using this porcelain clay body:
>
> EPK 25
> OM 4 25
> Minspar 25
> Silica 25
> + 1-2 % bentonite
>
>The body doesn't lend itself to throwing large round shapes which I would
>like to do. I am interested in any suggestions as to possible additions
>to my body that would improve its ability to stand up during the throwing
>process. I am aware of using torches to stiffen the pot. Also, I don't
>want to add any ingredients that will introduce iron because I am using
>pastel glazes on a white background.
>
>A single ingredient solution would be the best of all possible answers.
>
>Anybody out there have a suggestion?
>
>walter hartman
Hi Walter, I think your porcelain needs some flocculation. We typically add
2 to 3 lbs of magnesium sulphate (Epson Salts) to 1000 lbs of dry clay.
You do the math - dissolve the salts in hot water and add to the water of
plasticty you add to your clay body.
What is Minspar? I want an analysis of it. What cone are you firing at? I
should hasten to add these are not idle questions - if Min spar is a soda
spar there are other improvements to be made.
Ron Roy, Toronto, Canada
ARoth25182 on mon 8 apr 96
Hello Walter.
For throwing large pieces I add 1-2% Molochite to my porcelain body.
Molochite is a white substance which can be optained in varying mesh sizes
and which acts like grog and gives more tooth to the clay, as well as
lowering the shrinkage. When fired it fuses (I fire to cone 9 - 10) and
it fires white so that it dosn't interfere with painting.
Another possibility: Substitute Alumina for some of the silica. This
will also act as a very fine grog. It is possible to make a porcelain
substituting alumina for all the silica and this creates a very strong
fired product, although it costs quite alot more than silica.
I currently use a #6 tile clay porcelain body which I Modified by
substituting 2% Alumina hydrate for 2% of the silica. This addition seems
to have helped strenghten the clay and make for fewer drying cracks. Here
it is If you ( or anyone else) are (is) interested:
#6 tile clay 50
Custer feldspar 25
silica (325 M) 23
Alumina hydrate 2
talc 2
bentonite 2
for large pieces add
molochite 1-2%
All my work is painted which is why I use porcelain.
Its interesting to hear from others who mix they're own clay something
many potters don't do (understandable considering the work invoved). For
my part I like having controle over the formula. A Friend of mine had his
commercial stoneware body start bloating on him right after taking $16,000
worth of orders at one of the Rosen shows.
Good luck.
cpdunbar on thu 15 oct 98
i've been using Standard 112 clay body for electric kiln
it's time to buy more clay......
what are the majority of oxidation potters using today ?
name your poison............:)
Late at nite w/ Carolina in the Pines
cp
song on thu 19 apr 01
I want to fire my pieces(mostly bowls and cups) at cone 8 (1250 $B!n (B) =
for some
reasons, but the supplier has cone 5 or cone10 clay.
Which clay do I choose?
How different between cone 5clay fired cone8 temperature and cone 10clay
fired cone8 temperature?
Please tell me. I am new to clay.
Song
CINDI ANDERSON on thu 19 apr 01
It depends on the clay.
Cone 10 clays will certainly not be vitrified at Cone 8. Which isn't a p=
roblem
unless you are doing functional ware in which case it is.
Some Cone 5 clays will melt at Cone 8, which you definitely don't want. =
But probably
some Cone 5 clays actually require Cone 8 to vitrify.
You can test a piece for melting by firing it on a bisque tray made of a =
clay you
know is ok (ie fire a piece of cone 5 clay in a cone 10 tray. If it does=
n't melt,
you can test for vitrification. The following URL explains how.
http://www.bigceramicstore.com/Information/tip17.htm
Cindi
----------------
song wrote:
> I want to fire my pieces(mostly bowls and cups) at cone 8 (1250 $B!n (B=
) for some
> reasons, but the supplier has cone 5 or cone10 clay.
> Which clay do I choose?
> How different between cone 5clay fired cone8 temperature and cone 10cla=
y
> fired cone8 temperature?
> Please tell me. I am new to clay.
>
> Song
>
Ababi on fri 20 apr 01
Hello Song.
Take the ^10clay.If you will take the ^5 it might melt on your shelf. To see
it better put a plastic cup above the hole of the kiln at 1000C and watch
what happens to it.
You can try the ^5 clay, but do it on an extra shelf or old plate. If it
will not melt it might vitrified.
Ababi Sharon
ababisha@shoval.ardom.co.il
http://members4.clubphoto.com/ababi306910/
----- Original Message -----
From: "song"
To:
Sent: Thursday, April 19, 2001 10:11 PM
Subject: clay body
> I want to fire my pieces(mostly bowls and cups) at cone 8 (1250 $B!n (B)
for some
> reasons, but the supplier has cone 5 or cone10 clay.
> Which clay do I choose?
> How different between cone 5clay fired cone8 temperature and cone 10clay
> fired cone8 temperature?
> Please tell me. I am new to clay.
>
> Song
>
>
____________________________________________________________________________
__
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
>
Judith S. Labovitz on tue 4 nov 03
Hi...I'm in need of your advice....we are looking for a white porcelaneous
cone 10 clay body....any suggestions?????
many thanks
judy. greater lansing potters guild.....in rainy
mid-michigan btw....our fall show and sale is November 13,14,15...if any
of you will be in the East Lansing area then,,we'd love to see you...email
me off line for info..... .over 35 potters will have their work including
raku, low fire soda, high fire soda, oxidation and reduction...we usually
have 3000-4000 entries.....
Josie Jurczenia on fri 2 dec 05
Can anyone recommend a cone 5 clay that is buff like soldate 60? I am
experimenting with Calico (which is a little dark) and Grey stone (which is
a little grey). B-mix is too white. Does this sound like Goldilocks and the
3 Bears? Any suggestions would be appreciated. Thanks, Josie
Charles Moore on fri 2 dec 05
Hi, Josie,
> Can anyone recommend a cone 5 clay that is buff like soldate 60? I am
> experimenting with Calico (which is a little dark) and Grey stone (which
> is
> a little grey). B-mix is too white. >
Laguna's Calico is a very rough clay.
Quyle's Greystone is not a cone 5 clay; it matures at about ^9-10.
I would recommend Laguna's WC 400 (once known as Moroccan Sand); it fires a
warm tan in ^5-6 oxidation, a little darker in reduction at ^6. It has a
fair amount of grog to give it body.
Charles Moore
Sacramento
lela martens on sat 3 dec 05
Maybe try Plainsman med 340. sounds like what you are looking for, depending
on if your suppier carrys it.
Lela
>From: Charles Moore
>Reply-To: Clayart
>To: CLAYART@LSV.CERAMICS.ORG
>Subject: Re: clay body
>Date: Fri, 2 Dec 2005 17:28:35 -0800
>
>Hi, Josie,
>
>>Can anyone recommend a cone 5 clay that is buff like soldate 60? I am
>>experimenting with Calico (which is a little dark) and Grey stone (which
>>is
>>a little grey). B-mix is too white. >
>
>Laguna's Calico is a very rough clay.
>Quyle's Greystone is not a cone 5 clay; it matures at about ^9-10.
>
>I would recommend Laguna's WC 400 (once known as Moroccan Sand); it fires a
>warm tan in ^5-6 oxidation, a little darker in reduction at ^6. It has a
>fair amount of grog to give it body.
>
>Charles Moore
>Sacramento
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at
>melpots@pclink.com.
_________________________________________________________________
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Stephani Stephenson on sun 4 dec 05
Josie Wrote
Can anyone recommend a cone 5 clay that is buff like soldate 60? I am
experimenting with Calico (which is a little dark) and Grey stone
(which is
a little grey). B-mix is too white. Does this sound like Goldilocks
and the
3 Bears? Any suggestions would be appreciated. Thanks, Josie
Josie..sounds like you are using LAguna bodies
I don't know the soldate buff color, but their 52 Buff, or "52 buff
with sand" might work for you.
it is a lighter , yellow cream buff color.
haven't thrown with it. I use the 52 buff with sand for some
handbuilding and tile applications. It is a relatively fine bodied clay
Stephani Stephenson
steph@revivaltileworks.com
http://www.revivaltileworks.com
Bill Merrill on sun 29 jul 07
Rudy,
=20
OM4 will grey out the clay body some. The other clays help the iron in =
the Neuman red become more toasty when in combination with talc as a =
body flux in reduction. I only use spar if I was going to use this body =
in salt. If the Neuman red is left out a porcelain type clay could =
replace it. If you would buy a sack of each of those clays from Seattle =
Pottery, you could make 2 or 3 thousand gram batches by hand, make =
shrink bars, glaze tiles and throw some pots from each batch. This will =
help learn what the individual clays do. In fact a good test is to do a =
water of plasticity test on each individual clay, do shrinkage tests =
etc. There is a lot of information on how to do those tests in both of =
Daniel Rhodes books. I would suggest that you get Val Cushings =
handbook. The information in his handbook is from his classes at =
Alfred. I have notes from his lectures by date and time and my notes =
are very close to his handbook. It costs $22=20
=20
The formula that I sent , listed below is the formula for the clay body. =
The numbers you give are way off. Remember the batches we mixed was =
the basic formula with =BD again as much as each ingredient. Example =
Goldart was originally 25, so we took =BD of the 25 and added 12.5 more =
Gold Art to the mix as we were making a bach that added 50 % more of =
each ingredient.......(the Goldart was 37.5)
=20
The 3 clays we used instead of 30 lbs of OM4 was 10 lbs OM4, 10 lbs =
SPG Tennessee ball clay and 10 lbs M-44. =20
25 Cedar Heights Goldart
20 A.P. Green Mexico Fire clay
15 Neuman Red (Muddox Co,)=20
7 Talc
5 Neuman grog (Muddox Co,) More if you want
=20
The basic batch comes to 97 parts, plus the % of grog you want.
=20
If you make small batches you can do water of plasticity test so you =
will know how much water to use in big mixes. =20
=20
Bill =20
________________________________
From: RUDY BAUER [mailto:rudybauer@msn.com]=20
Sent: Sunday, July 29, 2007 9:04 PM
To: Bill Merrill
Subject: Re: clay body
=20
Actually I thought of some of the original tweaks you told us about such =
as some Tennessee ball clay in with the OM4 to lighten up a little =
however I love the way the goldart and grog show through that great =
red/brown color. As far as throwing...the best I've touched and I like =
several all ready. I'll need some more of it to make up a bunch of test =
tiles. Any more up at school? I've got several 12-14 inch large bowls =
made which I'll do some tomato red iron glaze on from Coleman's book if =
it fits well. At least I'll have a start for the fit. My current temoku =
with layered iron glazes over worked great. I definitely want to develop =
and stick with my own stoneware body for my work now. I'll give that Mt =
Baker white a thorough try and see how I may compare or give me a white =
to use. Got any ideas for a white that throws and works like that red? I =
know you do!!!
The steroids have made a huge difference in my comfort. I had my MRI =
Friday and see the neurosurgeon Wed. It's our Anniversary so we'll visit =
Silverdale for the Brewery on our way home. I'm afraid the several discs =
involved may make for a complicated fix. If he talks about metal in the =
back I'm out of there.
OK so that recipe was: OM4-45 pounds; goldart-27.5'; Newman =
Red-7.5'; Missouri Fire Clay-7'; Grog-5; talc-7'. Is that close? What =
brand was the Missouri clay?=20
I'm making my latest orders including three large 25 pound platters, =
6 Spaghetti bowls and large 12" serving bowl, three piece canister set, =
garlic keepers, nesting bowls set and 40 mugs. Where do those mugs go? =
I'll twist up the rest of the Southern Ice for the soda kiln. Is Jeff =
close to a load?
I'm supposed to be working tomorrow...RB
----- Original Message -----=20
From: Bill Merrill =20
To: RUDY BAUER =20
Sent: Sunday, July 29, 2007 12:07 PM
Subject: FW: clay body
=20
Rudy,=20
=20
This body is special to Nickerson and I !!!! Nick started with the =
basic formula in '68 at Alfred and I've altered and changed it over the =
years since '70. This is a magic body. It always seems to work well all =
the time. You can alter it in so many ways. Why I like this is it's =
slightly short and holds up to throwing any form. Perhaps you should =
make more pots with it and test your glazes before you make a ton of it
=20
=09
________________________________
From: Bill Merrill=20
Sent: Tuesday, July 10, 2007 2:57 PM
To: 'John/Jane Nickerson'
Cc: Bill Merrill
Subject: clay body
=20
Nick,
=20
I've changed the 'ol rubber body many times over the years and it's =
hard to make a bad body with the basic formula, even though materials =
have changed and I've substituted numerous clays at one time or another.
=20
Here's some suggestions for substitutions of clays.
=20
=20
=20
Total parts of OM4 originally was 30. To give more a more warm body I =
split the 30 parts into 1/3rds
=20
OM4............10 I always use 10 OM4
=20
10 M-377 ball clay, SPG Tennessee, Foundry Hill Cr=E8me (M-44), =
Kentucky Stone(M&D) =20
=20
10 Add 10 of the above of any of the above clays for each of the =
other two 10 parts
=20
=20
Goldart 25 =20
=20
Missouri Fireclay 20 (I've used Pine Lake Fireclay, but don't know if =
it's the same today or not today).
=20
Neuman red (H.C. Muddox Company) a plastic fireclay very similar to =
PBX Valentine 15-20 parts
=20
Talc 6-7 parts
=20
I use Neuman (H.C. Muddox Company) grog 5-7 parts (or more for hand =
building)
=20
I weigh my water and find what the basic body uses and go from there. =20
=20
=20
=20
I don't know what clays you can get there. Let me know dry clays they =
do have. I will look for the name of a company in Ohio that sent me a =
small sample of their grog. It was not bad, but not as good as the A.P, =
Green Pueblo grog. Nothing could beat that grog. =20
=20
I haven't located the plaster/water amounts for the bat molds yet, but =
I'll still look.
=20
Talk to you later,
=20
Bill
=20
=20
=20
=20
=20
=20
=20
=20
=20
=20
=20
=20
=20
=20
Ron Roy on thu 2 aug 07
Hi Bill,
Everything I know about cone 10 reduction clay bodies says this one is
going to be full of cristobalite - have you ever had any shivering
problems? Do you make ovenware?
Betsr regards - RR
>OM4 will grey out the clay body some. The other clays help the iron in
>the Neuman red become more toasty when in combination with talc as a body
>flux in reduction. I only use spar if I was going to use this body in
>salt. If the Neuman red is left out a porcelain type clay could replace
>it. If you would buy a sack of each of those clays from Seattle Pottery,
>you could make 2 or 3 thousand gram batches by hand, make shrink bars,
>glaze tiles and throw some pots from each batch. This will help learn
>what the individual clays do. In fact a good test is to do a water of
>plasticity test on each individual clay, do shrinkage tests etc. There is
>a lot of information on how to do those tests in both of Daniel Rhodes
>books. I would suggest that you get Val Cushings handbook. The
>information in his handbook is from his classes at Alfred. I have notes
>from his lectures by date and time and my notes are very close to his
>handbook. It costs $22
>
>
>
>The formula that I sent , listed below is the formula for the clay body.
>The numbers you give are way off. Remember the batches we mixed was the
>basic formula with =BD again as much as each ingredient. Example Goldart
>was originally 25, so we took =BD of the 25 and added 12.5 more Gold Art to
>the mix as we were making a bach that added 50 % more of each
>ingredient.......(the Goldart was 37.5)
>
>
>
> The 3 clays we used instead of 30 lbs of OM4 was 10 lbs OM4, 10 lbs SPG
>Tennessee ball clay and 10 lbs M-44.
>
>25 Cedar Heights Goldart
>
>20 A.P. Green Mexico Fire clay
>
>15 Neuman Red (Muddox Co,)
>
>7 Talc
>
>5 Neuman grog (Muddox Co,) More if you want
>
>
>
>The basic batch comes to 97 parts, plus the % of grog you want.
>
>
>
>If you make small batches you can do water of plasticity test so you will
>know how much water to use in big mixes.
>
>
>
>Bill
>
>________________________________
>
>From: RUDY BAUER [mailto:rudybauer@msn.com]
>Sent: Sunday, July 29, 2007 9:04 PM
>To: Bill Merrill
>Subject: Re: clay body
>
>
>
>Actually I thought of some of the original tweaks you told us about such
>as some Tennessee ball clay in with the OM4 to lighten up a little however
>I love the way the goldart and grog show through that great red/brown
>color. As far as throwing...the best I've touched and I like several all
>ready. I'll need some more of it to make up a bunch of test tiles. Any
>more up at school? I've got several 12-14 inch large bowls made which I'll
>do some tomato red iron glaze on from Coleman's book if it fits well. At
>least I'll have a start for the fit. My current temoku with layered iron
>glazes over worked great. I definitely want to develop and stick with my
>own stoneware body for my work now. I'll give that Mt Baker white a
>thorough try and see how I may compare or give me a white to use. Got any
>ideas for a white that throws and works like that red? I know you do!!!
>
> The steroids have made a huge difference in my comfort. I had my MRI
>Friday and see the neurosurgeon Wed. It's our Anniversary so we'll visit
>Silverdale for the Brewery on our way home. I'm afraid the several discs
>involved may make for a complicated fix. If he talks about metal in the
>back I'm out of there.
>
> OK so that recipe was: OM4-45 pounds; goldart-27.5'; Newman Red-7.5';
>Missouri Fire Clay-7'; Grog-5; talc-7'. Is that close? What brand was the
>Missouri clay?
>
> I'm making my latest orders including three large 25 pound platters, 6
>Spaghetti bowls and large 12" serving bowl, three piece canister set,
>garlic keepers, nesting bowls set and 40 mugs. Where do those mugs go?
>I'll twist up the rest of the Southern Ice for the soda kiln. Is Jeff
>close to a load?
>
> I'm supposed to be working tomorrow...RB
>
> ----- Original Message -----
>
> From: Bill Merrill
>
> To: RUDY BAUER
>
> Sent: Sunday, July 29, 2007 12:07 PM
>
> Subject: FW: clay body
>
>
>
> Rudy,
>
>
>
> This body is special to Nickerson and I !!!! Nick started with
>the basic formula in '68 at Alfred and I've altered and changed it over
>the years since '70. This is a magic body. It always seems to work well
>all the time. You can alter it in so many ways. Why I like this is it's
>slightly short and holds up to throwing any form. Perhaps you should make
>more pots with it and test your glazes before you make a ton of it
>
>
>
>=09
>________________________________
>
>
> From: Bill Merrill
> Sent: Tuesday, July 10, 2007 2:57 PM
> To: 'John/Jane Nickerson'
> Cc: Bill Merrill
> Subject: clay body
>
>
>
> Nick,
>
>
>
> I've changed the 'ol rubber body many times over the years and
>it's hard to make a bad body with the basic formula, even though materials
>have changed and I've substituted numerous clays at one time or another.
>
>
>
> Here's some suggestions for substitutions of clays.
>
>
>
>
>
>
>
> Total parts of OM4 originally was 30. To give more a more warm
>body I split the 30 parts into 1/3rds
>
>
>
> OM4............10 I always use 10 OM4
>
>
>
> 10 M-377 ball clay, SPG Tennessee, Foundry Hill Cr=E8me (M-44),
>Kentucky Stone(M&D)
>
>
>
> 10 Add 10 of the above of any of the above clays for each of
>the other two 10 parts
>
>
>
>
>
> Goldart 25
>
>
>
> Missouri Fireclay 20 (I've used Pine Lake Fireclay, but don't
>know if it's the same today or not today).
>
>
>
> Neuman red (H.C. Muddox Company) a plastic fireclay very similar
>to PBX Valentine 15-20 parts
>
>
>
> Talc 6-7 parts
>
>
>
> I use Neuman (H.C. Muddox Company) grog 5-7 parts (or more for
>hand building)
>
>
>
> I weigh my water and find what the basic body uses and go from ther=
e.
>
>
>
>
>
>
>
> I don't know what clays you can get there. Let me know dry clays
>they do have. I will look for the name of a company in Ohio that sent me
>a small sample of their grog. It was not bad, but not as good as the A.P,
>Green Pueblo grog. Nothing could beat that grog.
>
>
>
> I haven't located the plaster/water amounts for the bat molds yet,
>but I'll still look.
>
>
>
> Talk to you later,
>
>
>
> Bill
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>___________________________________________________________________________=
___
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.=
com.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Bill Merrill on sat 17 oct 09
I have not seen vinegar or Epsom salts used in a good throwing body by
potters I have known. Dave Shaner, Val Cushing, Ken Ferguson, Wally
Schwab, Jim & Nan McKinnell, Jim Flaherty, Rick St. John etc.
I wonder why? Is it because their clay bodies were formulated and
worked well for them that they don't need anything to make them
slippery etc. My clay body has 6 different clays in it. Three of which
I could replace with OM 4(or part of) , but I like to use other plastic
clays to alter the plasticity and fired color. The other clays are
A.P.Green Fire Clay( Wellesville can substitute A.P. Green), I also used
Pine Lake fireclay, Newman Red( I originally used PBX Valentine ) for
color, plus Talc or Custer spar for the flux, and grog. The combination
(8 ingrediants) I use makes a responsive body that stands up during
throwing, doesn't get mushy, can be shaped by collaring and expanding
and changed without the body collapsing. There are never any drying
cracks in the bottom of my pots and the body is relatively strong in the
dry state. I have used this body since 1968 and have made substitutions
for some of the clays as the clay supplies changed. I call it the 'Ol
rubber body because of its versatility. My point is if you formulate
and test your clays and formulate them correctly, vinegar and Epson
salts probably won't be needed. My clay is a little short for a few
days and gets considerably more plastic as the water is taken between
the platelets of clay. Clay is held together by suction, so the more
varied the particle sizes, the more water is in between the platelets
so they can slide over one another making the clay more "plastic".
I'm not trying to convince anyone to use or not use vinegar or Epson
salts, just saying what has worked for me. =3D20
=3D20
claybuds@ATT.NET on sat 17 oct 09
I use 0.3% addition of Epsom Salts to the water used to wet mix my porcelai=
=3D
n into a slurry, and have found it to be very effective at flocculation o=
=3D
f the mixture. The use of=3DC2=3DA0such an electrolyte to allow the clay pa=
rtic=3D
les to attract one another has meant better workability in the final produc=
=3D
t. Ron Roy described the action of Epsom Salts as that of aging=3DC2=3DA0o=
f t=3D
he clay, and I've found that to be true, either for porcelain or stoneware =
=3D
recipes.
David Beumee
=3DC2=3DA0 -------------- Original message from Bill Merrill COL.=3D
EDU>: --------------=3D20
> I have not seen vinegar or Epsom salts used in a good throwing body by=3D=
20
> potters I have known. Dave Shaner, Val Cushing, Ken Ferguson, Wally=3D20
> Schwab, Jim & Nan McKinnell, Jim Flaherty, Rick St. John etc.=3D20
>=3D20=3D20
> I wonder why? Is it because their clay bodies were formulated and=3D20
> worked well for them that they don't need anything to make them=3D20
> slippery etc. My clay body has 6 different clays in it. Three of which=
=3D
=3D20
> I could replace with OM 4(or part of) , but I like to use other plastic=
=3D
=3D20
> clays to alter the plasticity and fired color. The other clays are=3D20
> A.P.Green Fire Clay( Wellesville can substitute A.P. Green), I also used=
=3D
=3D20
> Pine Lake fireclay, Newman Red( I originally used PBX Valentine ) for=3D2=
0
> color, plus Talc or Custer spar for the flux, and grog. The combination=
=3D
=3D20
> (8 ingrediants) I use makes a responsive body that stands up during=3D20
> throwing, doesn't get mushy, can be shaped by collaring and expanding=3D2=
0
> and changed without the body collapsing. There are never any drying=3D20
> cracks in the bottom of my pots and the body is relatively strong in the=
=3D
=3D20
> dry state. I have used this body since 1968 and have made substitutions=
=3D
=3D20
> for some of the clays as the clay supplies changed. I call it the 'Ol=3D=
20
> rubber body because of its versatility. My point is if you formulate=3D2=
0
> and test your clays and formulate them correctly, vinegar and Epson=3D20
> salts probably won't be needed. My clay is a little short for a few=3D20
> days and gets considerably more plastic as the water is taken between=3D2=
0
> the platelets of clay. Clay is held together by suction, so the more=3D2=
0
> varied the particle sizes, the more water is in between the platelets=3D=
20
> so they can slide over one another making the clay more "plastic".=3D20
> I'm not trying to convince anyone to use or not use vinegar or Epson=3D2=
0
> salts, just saying what has worked for me.=3D20=3D20=3D20=3D20
>=3D20=3D20
>=3D20=3D20=3D20=3D20
Bruce Girrell on sat 17 oct 09
Bill Merrill wrote
> My point is if you formulate and test your clays and formulate them corre=
=3D
ctly, vinegar and Epson
salts probably won't be needed. =3D20
with which I agree entirely, but then added
> Clay is held together by suction, so the more
varied the particle sizes, the more water is in between the platelets
so they can slide over one another making the clay more "plastic".
Whoa, Bill. I was with you all the way, right up to that one sentence.
Statements such as that one are the sort of thing that Marian (Neon-cat) wa=
=3D
s adressing when she talked about putting some science into pottery.
First, clay is not held together by suction. I think you would be hard pres=
=3D
sed to describe a mechanism that produces suction in a clay body. On the ot=
=3D
her hand, if you look at electrical forces, capillary pressures and surface=
=3D
tension, I think you may find a better means of describing the forces betw=
=3D
een different parts of a clay body.
Second, the more varied the particle size the _less_ space there is for wat=
=3D
er. Consider a box filled with uniformly sized things - let's say basketbal=
=3D
ls. You can fit only so many basketballs into the box and there is lots of =
=3D
space around the basketballs. If you then add some ping pong balls, some of=
=3D
the open space between the basketballs will be filled in by the ping pong =
=3D
balls, making a denser pack. If you then add ball bearings to the mix, some=
=3D
of the remaining space between the ping pong balls and basketballs will be=
=3D
filled in with the ball bearings, increasing the density of the pack and r=
=3D
educing the remaining pore space even further. If you shrink the basketball=
=3D
s down to the size of silica grains, then you can see how the same sort of =
=3D
thing works in a clay body, with the ping pong balls and ball bearings bein=
=3D
g different clay materials. The more varied the particle size, the denser t=
=3D
he pack and the less space there is for water.
Matt Katz, along with Bill Carty, both from Alfred University, made a prese=
=3D
ntation at NCECA that addressed this topic a couple of years back (this was=
=3D
the same presentation that ignited the furor on Clayart regarding the idea=
=3D
that aging clay is not necessary if the clay body is properly formulated a=
=3D
nd mixed). Matt presented the concept of "green packing density" and showed=
=3D
that green packing density is directly related to workability of clay. So =
=3D
your observation that a clay body with a good mix of particle sizes has goo=
=3D
d working properties is supported by his work. Cracking is also minimized b=
=3D
y a higher green packing density, as there is more support between particle=
=3D
s and, hence, less shrinkage during the drying stage.
Finally, the oft-cited concept of clay platelets sliding over one another (=
=3D
sometimes with the tag line "like a deck of playing cards" added) is a gros=
=3D
s oversimplification. Only kaolin has platelets that might be thought of in=
=3D
that manner - and many, if not most, platelets are in "booklets", which me=
=3D
ans that their behavior will be closer to that of granular materials than t=
=3D
hat of a deck of cards. Ball clays have a far more complex structure and th=
=3D
e pore space is very tortuous. Because of their morphology, ball clays have=
=3D
a much larger surface area than kaolins, though they have much smaller par=
=3D
ticle size. The smectites (bentonite is the one we're most familiar with) h=
=3D
ave the smallest particle size and largest surface area.
The larger the surface area, the more difficult it will be to deflocculate =
=3D
the clay. In fact, there is a direct measure of a clay's - for lack of a be=
=3D
tter term - resistance to deflocculation. It's called cation exchange capac=
=3D
ity. If you have ever deflocculated a slip, you know that you can add a few=
=3D
drops of sodium silicate and it appears that nothing is happening. Then yo=
=3D
u add one more drop and, boom, the whole thing becomes deflocculated and be=
=3D
haves totally differently. You have just hit the cation exchange capacity o=
=3D
f the clay. Clay scientists use CEC as a measure of the surface area of cla=
=3D
ys. And they do it just as we deflocculate a slip. They add a deflocculant =
=3D
one tiny drop at a time until they observe the sudden change in character. =
=3D
The larger the surface area of the clay, the more deflocculant it requires =
=3D
to hit the CEC.=3D20
The upshot of all of this is that adding in these other clays (ball clays a=
=3D
nd a tiny bit of smectite) improves workability of the clay and will temper=
=3D
changes in workability resulting from changes due to reclaiming the clay o=
=3D
r other minor changes in composition. A clay with a smaller range of partic=
=3D
le sizes (such as a porcelain clay body) will be more likely to be adversel=
=3D
y affected by small changes in composition.
So your observations regarding the workability/plasticity of your clay body=
=3D
is spot on, but your understanding of why it behaves that way could use a =
=3D
little work.=3D20
Bruce Girrell=3D
James Freeman on sun 18 oct 09
On 10/17/09, Bruce Girrell wrote:
> Bill Merrill wrote
>
>
> with which I agree entirely, but then added
>
>> Clay is held together by suction,
> Whoa, Bill.
> First, clay is not held together by suction. I think you would be hard
> pressed to describe a mechanism that produces suction in a clay body. On =
the
> other hand, if you look at electrical forces, capillary pressures and
> surface tension, I think you may find a better means of describing the
> forces between different parts of a clay body.
Bruce...
I think perhaps Bill was using "suction" merely as a colloquialism for
surface tension (or probably surface energy). If so, I don't think it
is too terribly inaccurate as colloquialisms go. Many of us have used
the term precisely that way in non-scientific settings, such as when
trying to pick up a just washed saute pan that has become "suctioned"
to the countertop by the film of water.
Take care.
...James
--
James Freeman
"All I say is by way of discourse, and nothing by way of advice. I
should not speak so boldly if it were my due to be believed."
-Michel de Montaigne
http://www.jamesfreemanstudio.com
http://www.flickr.com/photos/jamesfreemanstudio/
http://www.jamesfreemanstudio.com/clayart/
Steve Mills on sun 18 oct 09
My Heroes as a student were (and still are to a certain extent) the traditi=
=3D
onal Potters who served their communities and used locally sourced material=
=3D
s. These good people would often prepare their local clay this year for use=
=3D
in the next, and since it was not a specially prepared body, but came with=
=3D
its own attendant idiosyncrasies this long period of "souring" was necessa=
=3D
ry. They also found that if they pee'd on it as well this helped to improve=
=3D
plasticity, as a good friend of mine put it: "you could throw it 'round co=
=3D
rners!". I have always baulked at using Urine as a plasticiser fo obvious r=
=3D
easons, but learnt that Vinegar was an excellent substitute, particularly i=
=3D
f the source was Cider - it smells a lot nicer!=3D0AOver quite a few years =
I =3D
have found that even a real "Class" prepared clay can be improved substanti=
=3D
ally by this treatment and needs much lass lubrication than before as a res=
=3D
ult, so it is part of my routine. =3D0ANow, at last I have found a local (t=
o =3D
me) clay with the ability to handle high temperatures. This is not a "perfe=
=3D
ct" clay, but it looks like it will work for me, and the fired samples look=
=3D
very promising indeed. One thing I am certain of though is that it's going=
=3D
to need the "accelerated souring" technique to aid its plastic qualities a=
=3D
nd ease my labours a bit.=3D0ALike you say Bill, this is what works for me.=
=3D
=3D0AVive la diff=3DE9rence.=3D0A=3D0ASteve=3D0ABath=3D0AUK=3D0A=3D0A=3D0A=
=3D0A=3D0A_____________=3D
___________________=3D0AFrom: Bill Merrill =3D0ATo: Cl=
ayar=3D
t@LSV.CERAMICS.ORG=3D0ASent: Sat, October 17, 2009 7:10:39 PM=3D0ASubject: =
clay=3D
body=3D0A=3D0AI have not seen vinegar or Epsom salts used in a good throwi=
ng b=3D
ody by=3D0Apotters I have known. Dave Shaner, Val Cushing, Ken Ferguson, W=
al=3D
ly=3D0ASchwab, Jim & Nan McKinnell, Jim Flaherty, Rick St. John etc.=3D0A=
=3D0AI w=3D
onder why? Is it because their clay bodies were formulated and=3D0Aworked =
w=3D
ell for them that they don't need anything to make them=3D0Aslippery etc. =
My=3D
clay body has 6 different clays in it. Three of which=3D0AI could replace=
w=3D
ith OM 4(or part of) , but I like to use other plastic=3D0Aclays to alter t=
he=3D
plasticity and fired color. The other clays are=3D0AA.P.Green Fire Clay( =
We=3D
llesville can substitute A.P. Green), I also used=3D0APine Lake fireclay, N=
ew=3D
man Red( I originally used PBX Valentine ) for=3D0Acolor, plus Talc or Cust=
er=3D
spar for the flux, and grog. The combination=3D0A(8 ingrediants) I use ma=
ke=3D
s a responsive body that stands up during=3D0Athrowing, doesn't get mushy, =
ca=3D
n be shaped by collaring and expanding=3D0Aand changed without the body col=
la=3D
psing. There are never any drying=3D0Acracks in the bottom of my pots and =
th=3D
e body is relatively strong in the=3D0Adry state. I have used this body si=
nc=3D
e 1968 and have made substitutions=3D0Afor some of the clays as the clay su=
pp=3D
lies changed. I call it the 'Ol=3D0Arubber body because of its versatility=
. =3D
My point is if you formulate=3D0Aand test your clays and formulate them co=
rr=3D
ectly, vinegar and Epson=3D0Asalts probably won't be needed. My clay is a =
li=3D
ttle short for a few=3D0Adays and gets considerably more plastic as the wat=
er=3D
is taken between=3D0Athe platelets of clay. Clay is held together by suct=
io=3D
n, so the more=3D0Avaried the particle sizes, the more water is in between=
t=3D
he platelets=3D0Aso they can slide over one another making the clay more "p=
la=3D
stic".=3D0AI'm not trying to convince anyone to use or not use vinegar or =
Ep=3D
son=3D0Asalts, just saying what has worked for me. =3D0A=3D0A=3D0A
Ron Roy on sat 31 oct 09
Hi Bill,
Probably because they were not using porcelain - especially at cone 6.
You can be sure they all knew about aged clay working better than fresh cla=
y
though.
Additives are necessary when you have some soluble sodium, potassium or
lithium present - they will all deflocculate a clay body given enough time.
If you have ever worked with deflocced clay you will soon realize the
benefits of reversing that situation.
RR
On Sat, Oct 17, 2009 at 2:10 PM, Bill Merrill wrote:
> I have not seen vinegar or Epsom salts used in a good throwing body by
> potters I have known. Dave Shaner, Val Cushing, Ken Ferguson, Wally
> Schwab, Jim & Nan McKinnell, Jim Flaherty, Rick St. John etc.
>
> I wonder why? Is it because their clay bodies were formulated and
> worked well for them that they don't need anything to make them
> slippery etc. My clay body has 6 different clays in it. Three of which
> I could replace with OM 4(or part of) , but I like to use other plastic
> clays to alter the plasticity and fired color. The other clays are
> A.P.Green Fire Clay( Wellesville can substitute A.P. Green), I also used
> Pine Lake fireclay, Newman Red( I originally used PBX Valentine ) for
> color, plus Talc or Custer spar for the flux, and grog. The combination
> (8 ingrediants) I use makes a responsive body that stands up during
> throwing, doesn't get mushy, can be shaped by collaring and expanding
> and changed without the body collapsing. There are never any drying
> cracks in the bottom of my pots and the body is relatively strong in the
> dry state. I have used this body since 1968 and have made substitutions
> for some of the clays as the clay supplies changed. I call it the 'Ol
> rubber body because of its versatility. My point is if you formulate
> and test your clays and formulate them correctly, vinegar and Epson
> salts probably won't be needed. My clay is a little short for a few
> days and gets considerably more plastic as the water is taken between
> the platelets of clay. Clay is held together by suction, so the more
> varied the particle sizes, the more water is in between the platelets
> so they can slide over one another making the clay more "plastic".
> I'm not trying to convince anyone to use or not use vinegar or Epson
> salts, just saying what has worked for me.
>
>
>
--
Ron Roy
15084 Little Lake Road
Brighton, Ontario, Canada
K0K 1H0
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