Ron Roy on wed 27 mar 96
Hello the list,
Does anyone know if old plaster (powder) can be made good again by
calcining? If so what temperature?
Thanks, RR
Louis Howard Katz on thu 28 mar 96
You can recalcine plaster by putting it in an oven at about 350 degrees
for a few hours. This turns the gypsum into plaster of Paris, but it will
may not revert any hardeners or modifiers that have been added to the
plaster. The plaster may need to be lightly ground to be usable.
Louis
P.S. I tried this on a small amount of plaster years ago, it worked O.K..
The information came from the mold instructor at P.C.A. named Petrus. I
don't know his last name.
***************************************************
*Louis Katz lkatz@falcon.tamucc.edu *
*Texas A&M University Corpus Christi *
*6300 Ocean Drive, Art Department *
*Corpus Christi, Tx 78412 *
*Phone (512) 994-5987 *
**************************************************
ktighe on mon 22 jul 96
Regarding plaster--- I make plaster molds for original sculpture and spent
far too much energy in the past seeking out perfect plaster. Two hours by
car from my home is a place where I would spend $20 for #1 Casting plaster,
available only in 100 lb. bags. Then I discovered a place only one hour
away that carried #1 Pottery plaster for about $10 in 50lb. bags. I would
have to arrange these purchases around trips into the city etc. I would
over-buy, and end up with plaster I couldn't use, because all plaster has a
shelf life and must be stored carefully. Now, in a paint supply store that
is stone's throw from my house, I buy Drywall Brand Plaster of Paris in 25
lb. bags for $4.50. It is an excellent product, produces a very hard mold,
and I can't believe all the time and energy I spent worrying about the
perfect plaster. Put me in the electric-chair purists; but plaster is
plaster is freaking plaster.--- Kenneth
Jonathan Kaplan on mon 22 jul 96
>----------------------------Original message----------------------------
>Regarding plaster--- I make plaster molds for original sculpture and spent
>far too much energy in the past seeking out perfect plaster. Two hours by
>car from my home is a place where I would spend $20 for #1 Casting plaster,
>available only in 100 lb. bags. Then I discovered a place only one hour
>away that carried #1 Pottery plaster for about $10 in 50lb. bags. I would
>have to arrange these purchases around trips into the city etc. I would
>over-buy, and end up with plaster I couldn't use, because all plaster has a
>shelf life and must be stored carefully. Now, in a paint supply store that
>is stone's throw from my house, I buy Drywall Brand Plaster of Paris in 25
>lb. bags for $4.50. It is an excellent product, produces a very hard mold,
>and I can't believe all the time and energy I spent worrying about the
>perfect plaster. Put me in the electric-chair purists; but plaster is
>plaster is freaking plaster.--- Kenneth
While I might, in very broad general non specific terms agree that plaster
is plaster is freaking plaster, or chemically speaking, they partial
hydration of a gypsum product, or the change in alpha gypsum to beta
gypsum, whatever, I would none the less disagree with you and state that
plaster is not palster is not freaking plaster.
While I share your travel concerns, it does a great dis-service to put
forward mis-information to this list. While it may work for you, and I am
pleased that you found this solution, I would never trust any product for
use in my shop that I didn't know diddly squat about, especially plaster.
There may be no perfect plaster for your particular application (but I
doubt this). But there are plasters, gypsum cements, that are superior in
formulation and use for specific applications. In fact, a very significant
portion of the ceramic industry uses industrial plaster for the resuklting
clay work, and my bet is that indeed, there are specific applications for
specific plasters. Go ahead, make some casting molds from Ceramical or
Ultracal 30 and then post your results to the list. I'm willing to bet that
your statement of plaster beign plaster being freaking plaster will be gone
by then.
Please get your information correct before making such bold assertions.
Jonathan
Jonathan Kaplan
Ceramic Design GroupLtd./Production Services
PO Box 775112
Steamboat Springs CO 80477
(970) 879-9139 voice and fax
call before faxing
"Show up, pay attention, tell the truth, don't be attatched to the results!"
Russel Fouts on thu 25 jul 96
PlasterCasters,
I've just made my first plaster mold (no great shakes, just a hump mold) and
read that it should now dry for TWO to THREE WEEKS before using it!?
Awww come on, can't I speed that up some?
Is it that it takes that long to dry out or are some chemical reactions still
taking place and hurrying it would make a weaker mold?
This will be the master for the working molds.
Russel ("Arthur Murry, taught me plaster in a hurry......")
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
* Russel Fouts, CI$: 100021,23,
Bruxelles, Belgium
Internet: 100021.23@CompuServe.Com
"It took more then one man to change my name to Shanghai Lil."
MD
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
!^NavFont01F0007NGHHH6A7DC6
Lori Wilkinson on thu 25 jul 96
At 09:16 AM 7/25/96 EDT, you wrote:
>----------------------------Original message----------------------------
>
> PlasterCasters,
>
> I've just made my first plaster mold (no great shakes, just a hump mold) and
>read that it should now dry for TWO to THREE WEEKS before using it!?
>
> Awww come on, can't I speed that up some?
>
Russel,
My experience has been that I have been able to use the mold as soon as it
felt dry to the touch and here in New Mexico drying it on a rack it took
less than a week. I am talking about a larger hump mold that I made 18"
platters with.
Lori Wilkinson Roswell NM
Jonathan Kaplan on tue 25 jul 00
I have always wondered why so many potters have such a fear of plaster in
the studio. I know it stems from a lack of education. Or from being
mis-informed or poorly educated.
There is a wonderful relationship between plaster and clay, and clay and
plaster. Having worked with this relationship for a long time I have come
to have a respect for both materials and their unlimited potentials.
Just as a side bar, the fear that many have of getting chunks of plaster in
their clay from a plaster wedging table surface surfaces many times on this
list and never ceases to amaze me. If the table is built correctrly and the
plaster mixed and poured correctly, there is really no problem. And yes, a
chunk of plaster in your pot will cause the section of the pot to blow off
due to the hydroscopic nature of plaster as well as to its expansion when
the pot is fired. However, an old slip casting/mold making trick in
adjusting for proper viscosity and specific gravity is too add a small
amount of powdered plaster to the slip mix. The resulting adjusted mix
never has been problematic in our shop on the times wse have needed to use
this method.
Plaster is one of those underused, underestimated and over feared materials
that is of such benefit to potters, often maligned because of mis-education
and mis-information.
Jonathan
Jonathan Kaplan, president
Ceramic Design Group
PO Box 775112
Steamboat Springs CO 80477
voice and fax 970 879-9139
jonathan@csn,net
http://www.sni.net/ceramicdesigin
Plant Location:
1280 13th Street Unit 13
Steamboat Springs CO 80487
(please use this address for all deliveries via UPS, comman carrier, FEd
Ex, etc.)
Tommy Humphries on tue 25 jul 00
Down here at Marshall Pottery, back in the days before the helpers got lazy
and we started using clay straight from the pug, ALL the potters clay was
wedged and rolled on plaster benches. This was upwards of 2-4 TONS of clay a
day without any problems of plaster getting into the clay. Of course we
used the plaster ball benches wet, to keep the clay from sticking, and I
think that this helped to cut down the chipping. Over the course of a years
time an 8" thick bench would have a pair of 6" deep depressions worn into
the surface from clay contact. Back in the "good ol days" all the potters
clay was pounded across a wire a minimum of 12 times to remove the air.
I also have wondered why so many were opposed to plaster, and why those who
weren't used it dry...
Tommy Humphries,
"`You know, it's at times like this, that I really wish I'd listened to what
my mother told me when I was young.'
`Why, what did she tell you?'
`I don't know, I didn't listen.'"
(Douglas Adams)
----- Original Message -----
From: "Jonathan Kaplan"
To:
Sent: Tuesday, July 25, 2000 8:03 AM
Subject: Plaster
> I have always wondered why so many potters have such a fear of plaster in
> the studio. I know it stems from a lack of education. Or from being
> mis-informed or poorly educated.
>
> Jonathan
>
> Jonathan Kaplan, president
> Ceramic Design Group
> PO Box 775112
> Steamboat Springs CO 80477
> voice and fax 970 879-9139
> jonathan@csn,net
> http://www.sni.net/ceramicdesigin
>
> Plant Location:
> 1280 13th Street Unit 13
> Steamboat Springs CO 80487
> (please use this address for all deliveries via UPS, comman carrier, FEd
> Ex, etc.)
>
>
____________________________________________________________________________
__
> 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.
>
David Hendley on wed 26 jul 00
I have to agree with Jonathon here. Plaster goes with clay
like, as our hometown boy Neil McCoy sings, coffee with a cup.
Yes, if you get a chunk of plaster in your clay it will cause
a blowout after firing.
You don't get plaster in your clay. You cover your wedging
table with canvas and you treat batts with care. You really
have to be pretty rough to break off chunks.
Not using plaster out of fear is like not using a gas kiln
out of fear. Sure, you can use an electric kiln all your life,
but you are severely limiting yourself. Nothing's better
than plaster for drying out clay, and it's also great for
press molds and sprigging. And of course making full
blown molds is an art in itself.
--
David Hendley
Maydelle, Texas
hendley@tyler.net
http://www.farmpots.com/
----- Original Message -----
From: Jonathan Kaplan
To:
Sent: Tuesday, July 25, 2000 8:03 AM
Subject: Plaster
| I have always wondered why so many potters have such a fear of plaster in
| the studio. I know it stems from a lack of education. Or from being
| mis-informed or poorly educated.
|
| There is a wonderful relationship between plaster and clay, and clay and
| plaster. Having worked with this relationship for a long time I have come
| to have a respect for both materials and their unlimited potentials.
|
| Just as a side bar, the fear that many have of getting chunks of plaster
in
| their clay from a plaster wedging table surface surfaces many times on
this
| list and never ceases to amaze me. If the table is built correctrly and
the
| plaster mixed and poured correctly, there is really no problem. And yes, a
| chunk of plaster in your pot will cause the section of the pot to blow off
| due to the hydroscopic nature of plaster as well as to its expansion when
| the pot is fired. However, an old slip casting/mold making trick in
| adjusting for proper viscosity and specific gravity is too add a small
| amount of powdered plaster to the slip mix. The resulting adjusted mix
| never has been problematic in our shop on the times wse have needed to use
| this method.
|
| Plaster is one of those underused, underestimated and over feared
materials
| that is of such benefit to potters, often maligned because of
mis-education
| and mis-information.
|
| Jonathan
|
| Jonathan Kaplan, president
| Ceramic Design Group
| PO Box 775112
| Steamboat Springs CO 80477
| voice and fax 970 879-9139
| jonathan@csn,net
| http://www.sni.net/ceramicdesigin
mel jacobson on wed 26 jul 00
after 35 years of teaching clay in a high school, the mere
mention of plaster gave me shivers. if it is possible, a high school kid
will get plaster in clay.
it always shows up in the big fount i make for a church.
worth a great deal of money, and i did not make two. they need it for
easter and i fire on good friday.....huge plaster pop right in the middle.
(use a big black marker, grinder, more felt pen. re/do the commission.
if you work alone, know how to control plaster, it is a wonderful
tool for potters. as for me, never have a drop in my studio. it will find
me, no matter what i do.
mel
http://www.pclink.com/melpots
written from the farm in wisconsin
James Bledsoe on wed 26 jul 00
plaster is just calcium
when we wedge on plaster and it comes off in molecules it is a little flux
in the clay no problem
Tom Buck on thu 27 jul 00
James B:
My reading of your post, that plaster is calcium, makes me say "Ah
no"
----
Plaster (of Paris) starts off as a mineral, a natural deposit of
calcium sulfate anhydrous or duohydrate (2H2O, aka gypsum). As such
neither will react with water (set) to form familiar molds. For this to
happen the mineral is processed into calcium sulfate, hemi-hydrate
(0.5H2O), pulverized, etc. The bags of plaster that potters receive have a
shelf-life of approx. six months, or less, depending on storage conditions
(low moisture helps).
When a measured amount of PP is added to a known amount of water,
the PP becomes a form of gypsum, that is, it becomes an "ordered" solid
(crystalline) that is strong and durable. Like the mixing of concrete, the
ratio of water to plaster is critical to getting a durable solid.
For potters, I suggest that the best source of info on forming
plaster shapes, is the book by Donald Frith, namely "mold making for
ceramics".
peace. tom b.
Tom Buck ) tel: 905-389-2339
(westend Lake Ontario, province of Ontario, Canada).
mailing address: 373 East 43rd Street,
Hamilton ON L8T 3E1 Canada
Millie Carpenter on fri 28 jul 00
Tom
does plaster plaster come with sell by dates or experation dates? I don't remember
seeing a code on previous bags.
Millie in Md.
>> The bags of plaster that potters receive have ashelf-life of approx. six months, or
>> less, depending on storage conditions (low moisture helps).
>>
>>
Janet Kaiser on fri 28 jul 00
I was so cold by the time I got to bed last night, I
could not get to sleep and so lay there thinking
beautiful thoughts...
Suddenly "plaster" popped up. (Yes, I know "Get a
life"). Apart from mulling over someone thinking
plaster is calcium (isn't it calcinated or dehydrated
gypsum?)
Anyway, it took me back to a big mega buck bid I worked
on at a petro-chemical engineering company in Germany
back in the early 1980s. They were introducing new
technology which would reduce pollution at a refinery
in the Soviet Union.
The bi-product of the proposed
Rauchgasentschwefelungsanlage (yes, that is one word)
was high grade plaster.
So all you folk who presume plaster is only made from
squeaky clean and natural products like gypsum please
beware. As far as I remember, the only way this other
plaster (which presumably would contain heavy metals
and other nasties like dioxins) differed from high
quality Plaster of Paris, was a slight yellow tinge. It
was also a tad softer than P.o.P. but equally
durable.
This technology was licensed from a firm in the US. It
was 1982/3 and I left in 1984/5, so I do not know how
many of these Rauchgasentschwefelungsanlagen went into
production around the world. Again I can only presume
some did, because it was at a time when many
manufacturing companies were being forced by
legislation and the environmental lobby to clean up
their act.
Just thought it worth a mention... Please do not ask me
the finer technical points. It is so long ago and you
know how those little grey cells drop everything they
need not remember. I also have difficulty telling you
anything from that previous life in English... That
part of my brain only works in German! :-)
Janet Kaiser - Also thinking of Joyce and her owls.
Does she realise how many people collect ceramic owls?
Now the word is out, there will be owl fanciers
arriving in droves. Hope they do not trample the desert
flat...
The Chapel of Art . Capel Celfyddyd
HOME OF THE INTERNATIONAL POTTERS' PATH
Criccieth LL52 0EA, GB-Wales Tel: (01766) 523570
E-mail: postbox@the-coa.org.uk
WEBSITE: http://www.the-coa.org.uk
Ingeborg Foco on sun 24 feb 02
I'm having difficulty locating Pottery #1 plaster for my new =
wedging/recycling table. The only thing available locally seems to be =
Uni Kal Veneer Plaster.
The ingredients are Plaster of Paris, Calcium Hydroxide and quarts. Is =
there anyone who has experience in using veneer plaster for a wedging =
table and hump molds? =20
Thanks in advance for any information.
Sincerely,
Ingeborg
John Rodgers on wed 2 jan 08
Bill,
I love my plaster bats. I started using them not long after I started
throwing on the wheel. Up until then my use of plaster has been in the
real of molds and mold making.
My throwing bats are made up from the "pure and Simple" bat system,
which consists of refomed plastic molds for the bats, and two different
sized keyways that fasten to the wheel head. Though I have used a lot of
other kinds of bats, mostly when I'm elsew3here and throwing, when I'm
in my studio I much prefer the plaster bats. I hear a lot of talk about
how plaster will get in the clay, etc, but I have never had that problem
when throwing, nor having it get into the scrap from throwing. I'm still
throwing with plaster bats I made up over ten years ago.
Two features I especially like are the ability to do a bit of wedging on
the bat while at the wheel, to remove any excess water and dry the clay
a bit, and I especially like the self releasing feature when the clay
object is dried on the base just a bit by the plaster, to the point that
the clay loses it's grip on the bat.and pops loose. It makes for a very
nice, smooth bottom. If the vessel is thrown well, there is no need to
trim out the bottom. of vessel.
Regards,
John Rodgers
Chelsea, aL
Bill Merrill wrote:
> Steve,
>
>
>
> I have used plaster bats since 1966. I took plaster class at Alfred in
> '73 and it was an eye opener to really learn how to make and use
> plaster. Wally Higgins was a great teacher. I have used plaster bats
> that I cast and the molds were part of the system Ted Randall developed
> in '49. There is a removable wheel head and flat heads for the Randall
> wheel. The bucket head accepts bats made from aluminum bat molds. I
> use 8", 12" 16" and 20 inch plaster bats. It is very convenient to
> throw pitchers for example on a bat, lift off the bat , let it set and
> trim it while still attached to the mold and then put it back on the
> wheel and trim the base if necessary. To remove the pitcher from the
> wheel I merely slide a thin, sharpened spatula under the pot and turn
> the wheel which pops off the pitcher from the bat. Not many people know
> this system, because there aren't any New Randall wheels being made. I
> am going to get a Soldner wheel and have them put on a tapered shaft so
> I can use use the bucket heads I have. A nice thing about plaster is it
> draws moisture out of the bottom of the pot and is similar in hardness
> to the walls of the pot. It is also convenient for Casseroles so if you
> have to adjust the lip you can as the can be turned upside down to see
> if it fits before cutting it off the bat. I guess I am just someone
> from an old school of potters and will continue to use plaster in my
> ceramics. Dave Shaner, Bob Turner, Val Cushing, Victor Babu, Ken
> Ferguson were just a few well known potters that used plaster bats. I
> have found that the use of bats this way raised my production
> tremendously.
>
>
>
> Regards,
>
>
>
> Bill Merrill
>
>
>
> ______________________________________________________________________________
> Clayart members may send postings to: clayart@lsv.ceramics.org
>
> You may look at the archives for the list, post messages, or change your
> subscription settings here: http://www.acers.org/cic/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at melpots2@visi.com
>
>
>
Bill Merrill on wed 2 jan 08
Steve,
=20
I have used plaster bats since 1966. I took plaster class at Alfred in
'73 and it was an eye opener to really learn how to make and use
plaster. Wally Higgins was a great teacher. I have used plaster bats
that I cast and the molds were part of the system Ted Randall developed
in '49. There is a removable wheel head and flat heads for the Randall
wheel. The bucket head accepts bats made from aluminum bat molds. I
use 8", 12" 16" and 20 inch plaster bats. It is very convenient to
throw pitchers for example on a bat, lift off the bat , let it set and
trim it while still attached to the mold and then put it back on the
wheel and trim the base if necessary. To remove the pitcher from the
wheel I merely slide a thin, sharpened spatula under the pot and turn
the wheel which pops off the pitcher from the bat. Not many people know
this system, because there aren't any New Randall wheels being made. I
am going to get a Soldner wheel and have them put on a tapered shaft so
I can use use the bucket heads I have. A nice thing about plaster is it
draws moisture out of the bottom of the pot and is similar in hardness
to the walls of the pot. It is also convenient for Casseroles so if you
have to adjust the lip you can as the can be turned upside down to see
if it fits before cutting it off the bat. I guess I am just someone
from an old school of potters and will continue to use plaster in my
ceramics. Dave Shaner, Bob Turner, Val Cushing, Victor Babu, Ken
Ferguson were just a few well known potters that used plaster bats. I
have found that the use of bats this way raised my production
tremendously.
=20
Regards,
=20
Bill Merrill
=20
Rogier Donker on thu 3 jan 08
Hey Bill :-)
All this talk about bats.... I was beginning to think
I was in the minority when it came to throwing on plaster bats. Like
you I "grew up " with plaster bats. The Amaco wheels all used to
come with the Ted Randall system. "Special head and bat casting ring"
One made their own bats as part of the ceramic process. Back then
(the sixties) everybody who was anybody on the ceramic scene threw on
plaster bats. Some of the bats in my studio are over thirty years
old... still going strong, thank you. Sometimes I think the old ways
are a lot better than the modern newfangled ways. Then again that is
probably an argument that the generation before us had too...;-) Time
marches on. My kiln, "Mama Martha." is up for sale... (located in
Southwest Indiana)
Rogier
P.S. See us on the web at http://www.donkerstudio.org
James and Sherron Bowen on thu 3 jan 08
How does one make a casting ring for these types of wheel heads? I have an
Amaco and a Randall. I don't have the "bucket" head for the Randall but
would love to find one.
JB
----- Original Message -----
From: "Rogier Donker"
To:
Sent: Thursday, January 03, 2008 7:37 AM
Subject: plaster
C.T. Wagoner on thu 3 jan 08
Hi JB,
Amaco sells the ring for their wheel head. I have four if you would like to
borrow them. It is handy to make them three of four at a time. Make them
upside down on a pane of glass. Use Hydro-cal or Ultra-cal for long lasting
hard bats.
Chuck the Billie Creek Potter
-------------------------------------------------------------------
How does one make a casting ring for these types of wheel heads? I have an
Amaco and a Randall. I don't have the "bucket" head for the Randall but
would love to find one.
JB
-
Rogier Donker on sat 5 jan 08
Yo! JB!
Amaco sells the casting rings for the special heads... 1 800 925
5195 "Tammy" at extension 322
Rogier
P.S. See us on the web at http://www.donkerstudio.org
| |
|
