Snail Scott on fri 1 dec 00
USG #1 is O.K., but #1 Pottery Plaster (also USG) is better
for most molds because it is more absorbent. This is less
important for hump/slump molds than for slip-casting, of
course. You may need to go to a specialty supplier for
Pottery Plaster; most building-supply places can order it,
but don't stock it. Hydrocal is very, very strong but not
very absorbent. It's almost impossible to drill, file,
or scrape. I wouldn't use it except to make a permanent
pattern for multiple mold making.
-Snail
At 02:11 PM 12/1/00 -0600, you wrote:
>Hello,
>
>I have been roaming the web and making phone calls for the past two days
>trying to figure out what kind of plaster I should use and where I can find
>it locally. What appeared to be a simple task turned into a nightmare. A
>likely candidate is USG #1, but I would have to do back flips to get
>it. What's the story with Hydrocal and which one if any?
>
>All I want to do is a simple hump mold. *sniff* ;) Those of you who have
>experience in mold making, what do you use and why? Also, anything you can
>tell me in terms of pitfall, would be greatly appreciated.
>
>TIA,
>
>Fabienne
>--
>Milky Way Ceramics http://www.milkywayceramics.com/
michael wendt on fri 1 dec 00
Hi Fabienne,
I make drape molds out of particle board for short run orders. They are
light, tough and release easily when sprayed with WD-40 or some other light
oil or cooking spray. I always make my drapes in the hollow form so that as
the clay shrinks, it pulls away from the mold rather than getting caught as
it would with a positive drape. For deeper molds, I stack up multiple sheets
of particle board, cut on the jig saw, glue and sand them and then put in
the bottom last. I radius the curve transitions in the forms with Durham's
rock hard water putty. Best of all, if you want to make a plaster mold
later, you can finish the wooden one and make a plaster master positive to
make as many molds as you want.
Regards,
Michael Wendt wendtpot@lewiston.com
-----Original Message-----
From: Fabienne Micheline Cassman
To: CLAYART@LSV.CERAMICS.ORG
Date: Friday, December 01, 2000 2:19 PM
Subject: Choosing the Right Plaster
>Hello,
>
>I have been roaming the web and making phone calls for the past two days
>trying to figure out what kind of plaster I should use and where I can find
>it locally. What appeared to be a simple task turned into a nightmare. A
>likely candidate is USG #1, but I would have to do back flips to get
>it. What's the story with Hydrocal and which one if any?
>
>All I want to do is a simple hump mold. *sniff* ;) Those of you who have
>experience in mold making, what do you use and why? Also, anything you can
>tell me in terms of pitfall, would be greatly appreciated.
>
>TIA,
>
>Fabienne
>--
>Milky Way Ceramics http://www.milkywayceramics.com/
>
> Yes, I have learned from my mistakes...
> I can reproduce them exactly.
>
>___________________________________________________________________________
___
>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.
>
Jonathan Kaplan on fri 1 dec 00
>Hello,
>
>I have been roaming the web and making phone calls for the past two days
>trying to figure out what kind of plaster I should use and where I can find
>it locally. What appeared to be a simple task turned into a nightmare. A
>likely candidate is USG #1, but I would have to do back flips to get
>it. What's the story with Hydrocal and which one if any?
>
>All I want to do is a simple hump mold. *sniff* ;) Those of you who have
>experience in mold making, what do you use and why? Also, anything you can
>tell me in terms of pitfall, would be greatly appreciated.
>
>TIA,
>
>Fabienne
>
You want to use USG Pottery #1 Plaster. It is the industry standard. Use
this for casting molds, hump molds, etc. etc. It is designed to absorb
water from the clay and needs to be used at a consistency of 70 parts water
to 100 parts plaster. USG will send you a plaster calculator just for
asking that, using some basic geometric forms, will help you arrive at the
correct weight of plaster and weight of water for a specific volume.
Hydrocal, Ultracal 30, Hydrostone, are gypsum cements and all have super
low absorbancy and are used mostly for tooling... blocks, cases, etc. etc.
Jonathan
Jonathan Kaplan
Ceramic Design GroupLTD/Production Services
PO Box 775112
Steamboat Springs, CO 80477
(970) 879-9139 voice and fax
http://www.sni.net/ceramicdesign
UPS: 1280 13th St. Unit13
Steamboat Springs, CO 80487
Veronica Honthaas on fri 1 dec 00
I just go down to the local a building store and they order it for me.
Usually have it in a less then a week. Veronica
Cindy Strnad on fri 1 dec 00
Fabienne,
You might be best off to purchase the highest grade of plaster available at
the busiest hardware store near you. Number 1 pottery plaster is probably
the ideal, but only if it's fresh. Hardware stores tend to have a higher
turnover rate of merchandise than art stores. Freshness is the most
important thing with plaster. Everything else falls in line behind that.
Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
USA
earthenv@gwtc.net
http://www.earthenvesselssd.com
Stephani Stephenson on fri 1 dec 00
Fabienne wrote
All I want to do is a simple hump mold. *sniff* ;) Those of you who
have
experience in mold making, what do you use and why?
Hi Fabienne
I would suggest # 1 Pottery plaster for your hump mold
It is less expensive than hydrocal, and yet is stronger than typical
"plaster of Paris" found at craft or hardware stores. Also it has a
good porosity, This is helpful because when you place a slab over the
mold, moisture from the clay is absorbed by the plaster at somewhat the
same rate as moisture evaporates into the air. (This isn't any kind of
exacting scientific statement , it's just what I have noticed over the
years.) You want the plaster to wick some moisture away from the clay
because it means that relatively even drying is taking place on both
surfaces of the slab as it stiffens. Also the plaster's porosity helps
the mold dry out after use.
For the most part # 1 pottery plaster is very useful and durable.
We use hydrocal in the making of ram press molds, but the mixing and
moldmaking process is quite different.
If you have some hydrocal on hand, and want to use it up rather than
buying new plaster, however, you could certainly make a hump mold with
it.
Stephani Stephenson
Marcia Selsor on fri 1 dec 00
Fabienne,
Hydrocal is harder than US#1, If you want durability in your mold use
hydrocal. It lasts longer. US#1 is somewhat softer although is very
adequate for molds. Even lumber yard casting plaster will work for a
hump mold.
Marcia
> Fabienne Micheline Cassman wrote:
>
> > Hello,
> >
> > I have been roaming the web and making phone calls for the past two days
> > trying to figure out what kind of plaster I should use and where I can find
> > it locally. What appeared to be a simple task turned into a nightmare. A
> > likely candidate is USG #1, but I would have to do back flips to get
> > it. What's the story with Hydrocal and which one if any?
> >
> > All I want to do is a simple hump mold. *sniff* ;) Those of you who have
> > experience in mold making, what do you use and why? Also, anything you can
> > tell me in terms of pitfall, would be greatly appreciated.
> >
> > TIA,
> >
> > Fabienne
> > --
> > Milky Way Ceramics http://www.milkywayceramics.com/
> >
> > Yes, I have learned from my mistakes...
> > I can reproduce them exactly.
> >
> > ______________________________________________________________________________
> >
> > 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.
>
> --
> Earl Brunner
> http://coyote.accessnv.com/bruec
> mailto:bruec@anv.net
>
> ______________________________________________________________________________
> 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.
--
Marcia Selsor
selsor@imt.net
http://www.imt.net/~mjbmls
http://www.imt.net/~mjbmls/Tuscany2001.html
Fabienne Micheline Cassman on fri 1 dec 00
Hello,
I have been roaming the web and making phone calls for the past two days
trying to figure out what kind of plaster I should use and where I can find
it locally. What appeared to be a simple task turned into a nightmare. A
likely candidate is USG #1, but I would have to do back flips to get
it. What's the story with Hydrocal and which one if any?
All I want to do is a simple hump mold. *sniff* ;) Those of you who have
experience in mold making, what do you use and why? Also, anything you can
tell me in terms of pitfall, would be greatly appreciated.
TIA,
Fabienne
--
Milky Way Ceramics http://www.milkywayceramics.com/
Yes, I have learned from my mistakes...
I can reproduce them exactly.
Earl Brunner on fri 1 dec 00
I don't, and haven't used plaster in my studios for many years. What
works well for me is bisque, I throw the hump mold shape I want on the
wheel, or if not round, form it out of a slab over some other form.
Once fired in a bisque they work very well. They don't absorb quite as
much moisture as plaster but they are a nice alternative.
Fabienne Micheline Cassman wrote:
> Hello,
>
> I have been roaming the web and making phone calls for the past two days
> trying to figure out what kind of plaster I should use and where I can find
> it locally. What appeared to be a simple task turned into a nightmare. A
> likely candidate is USG #1, but I would have to do back flips to get
> it. What's the story with Hydrocal and which one if any?
>
> All I want to do is a simple hump mold. *sniff* ;) Those of you who have
> experience in mold making, what do you use and why? Also, anything you can
> tell me in terms of pitfall, would be greatly appreciated.
>
> TIA,
>
> Fabienne
> --
> Milky Way Ceramics http://www.milkywayceramics.com/
>
> Yes, I have learned from my mistakes...
> I can reproduce them exactly.
>
> ______________________________________________________________________________
>
> 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.
--
Earl Brunner
http://coyote.accessnv.com/bruec
mailto:bruec@anv.net
Greg Lamont on fri 1 dec 00
Hi Fabienne,
>From what I've been able to discern from reading about the various plaster
types and their attributes, in the Great Lakes Clay catalog, you should be
able to use good ol' #1 pottery plaster. Puritan pottery plaster is said to
be denser and stronger than #1 Pottery plaster and might be a good choice if
the mold will be subject to heavy use. Hydrocal is stronger yet and is
recommended for making case molds and master molds for porduction. Ultracal
is even stronger and hydrostone is is used for die production, etc. I've
made hump molds very successfully with just using Plaster of Paris from my
local Lowe's Home Improvement center. I only use them occasionally,
however. Perhaps Johnathan Kaplan will weigh in on this as he has great
experience with moldmaking?
All the best,
Greg
-----Original Message-----
From: Fabienne Micheline Cassman
To: CLAYART@LSV.CERAMICS.ORG
Date: Friday, December 01, 2000 2:48 PM
Subject: Choosing the Right Plaster
>Hello,
>
>I have been roaming the web and making phone calls for the past two days
>trying to figure out what kind of plaster I should use and where I can find
>it locally. What appeared to be a simple task turned into a nightmare. A
>likely candidate is USG #1, but I would have to do back flips to get
>it. What's the story with Hydrocal and which one if any?
>
>All I want to do is a simple hump mold. *sniff* ;) Those of you who have
>experience in mold making, what do you use and why? Also, anything you can
>tell me in terms of pitfall, would be greatly appreciated.
>
>TIA,
>
>Fabienne
>--
>Milky Way Ceramics http://www.milkywayceramics.com/
>
> Yes, I have learned from my mistakes...
> I can reproduce them exactly.
>
>___________________________________________________________________________
___
>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.
>
Tommy Humphries on sat 2 dec 00
As far a as freshness of plaster is concerned, you can refresh it by heating
it to around 700 deg. F. to remove all the moisture.
I once needed just a small amount of plaster to make a patch, and did not
have time to go into town, so I stripped off the paper backing from some
gypsum wallboard and heated it (about a pound) with a propane torch , while
crushing it with a mortar and pestle. when I had a fine HOT powder I added
water and mixed. It set up smooth and hard in the normal time.
I understand that in Europe they are beginning to recycle wallboard instead
of trucking it to the landfill.
Tommy Humphries
Photos here http://albums.photopoint.com/j/AlbumIndex?u=939179&a=6869600
----- Original Message -----
From: "Cindy Strnad"
To:
Sent: Friday, December 01, 2000 7:21 PM
Subject: Re: Choosing the Right Plaster
> Fabienne,
>
> You might be best off to purchase the highest grade of plaster available
at
> the busiest hardware store near you. Number 1 pottery plaster is probably
> the ideal, but only if it's fresh. Hardware stores tend to have a higher
> turnover rate of merchandise than art stores. Freshness is the most
> important thing with plaster. Everything else falls in line behind that.
>
>
> Cindy Strnad
> Earthen Vessels Pottery
> RR 1, Box 51
> Custer, SD 57730
> USA
> earthenv@gwtc.net
> http://www.earthenvesselssd.com
>
>
____________________________________________________________________________
__
> 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.
>
Louis Katz on sat 2 dec 00
It can be hard to get #1 pottery plaster from local suppliers. Apparently there
are two USG plants. One produces #1 pottery, the other doesn't.If your local
plaster supplier gets thier plaster from the plant that doesn't, well, its not
available and you should order it from another supplier. Most Ceramic suppliers
carry it.
There are probably good mixing directions in the archives.
Louis
Jonathan Kaplan wrote:
> >Hello,
> >
> >I have been roaming the web and making phone calls for the past two days
> >trying to figure out what kind of plaster I should use and where I can find
> >it locally. What appeared to be a simple task turned into a nightmare. A
> >likely candidate is USG #1, but I would have to do back flips to get
> >it. What's the story with Hydrocal and which one if any?
> >
> >All I want to do is a simple hump mold. *sniff* ;) Those of you who have
> >experience in mold making, what do you use and why? Also, anything you can
> >tell me in terms of pitfall, would be greatly appreciated.
> >
> >TIA,
> >
> >Fabienne
> >
>
> You want to use USG Pottery #1 Plaster. It is the industry standard. Use
> this for casting molds, hump molds, etc. etc. It is designed to absorb
> water from the clay and needs to be used at a consistency of 70 parts water
> to 100 parts plaster. USG will send you a plaster calculator just for
> asking that, using some basic geometric forms, will help you arrive at the
> correct weight of plaster and weight of water for a specific volume.
>
> Hydrocal, Ultracal 30, Hydrostone, are gypsum cements and all have super
> low absorbancy and are used mostly for tooling... blocks, cases, etc. etc.
>
> Jonathan
>
> Jonathan Kaplan
> Ceramic Design GroupLTD/Production Services
> PO Box 775112
> Steamboat Springs, CO 80477
> (970) 879-9139 voice and fax
> http://www.sni.net/ceramicdesign
>
> UPS: 1280 13th St. Unit13
> Steamboat Springs, CO 80487
>
> ______________________________________________________________________________
> 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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