lili krakowski on fri 27 feb 04
I know very little about plaster, and need help.
In September I bought some moulding plaster, used half the bag, wrapped =
the rest tightly in its own bag and put in a bucket. Bucket stored in a =
shed that is dry but totally unheated--i.e. it is below freezing in =
there a lot.
Reopened bag just now, made a sample batch (very small)
The plaster is granular, sort of like pie crust when one has just cut =
the shortening in, something like cornmeal except uneven. =20
Is there any sense using it for a mold for my tiny bricks? Would =
sieving do anything except make a mess? Would bringing the dry plaster =
to room temp do anything?
Is a totally sealed bag of plaster bought at same time have a chance of =
being "good"? =20
Many thanks
Lili Krakowski
Be of good courage
Lou Roess on fri 27 feb 04
on 2/27/04 6:37 AM, lili krakowski at mlkrakowski@CITLINK.NET wrote:
> Reopened bag just now, made a sample batch (very small)
> The plaster is granular, sort of like pie crust when one has just cut the
> shortening in, something like cornmeal except uneven.
>
> Is there any sense using it for a mold for my tiny bricks? Would sieving do
> anything except make a mess? Would bringing the dry plaster to room temp do
> anything?
>
> Is a totally sealed bag of plaster bought at same time have a chance of being
> "good"?
Lila, The following should answer these questions.
"1. Always check and see if your plaster is good. Run your hand through
the dry plaster and check for little nodules (lumps) of plaster. This
indicates old plaster and now matter what you do the mold will be soft
and brittle. If the plaster is very fine and "dusty" it is usually new
and suitable for mold making. If you have old plaster and you strain it
with a kitchen flour sifter, you will get the lumps out, but it will set
too quickly and be incredibly soft mold. Use new plaster, especially when
making one-off molds. These lumps are caused by the dry plaster absorbing
moisture from the air and the plaster is simply too old. It will absorb
this moisture through the bag the plaster is in. "
This exerpt is from a posting to Clayart by Clifton Cardin on Nov 7, 2003
The subject was "no subject" so you'd have to search by his name, or if you
want I can forward it to you . There was lots of useful information in the
post.
Lou in Colorado
Craig Dunn Clark on fri 27 feb 04
Lily, sounds to me like your plaster is "seeded." It is no longer of
much use...at least not for what it was intended. I had a similar problem a
little over a year ago and called the folks that manufacter the stuff and
was told that whenever a bag of plaster is opened it is best to use it,
otherwise it will absorb moisture from the atmoshpere and begin to react.
This leads to the nasty lumpy stuff that you have described.
Having said this it also sounds like you took extraordinary precautions
to prevent seeding. If you are certain that the water/plaster mix is correct
then you might ask your supplier how long the bag had been sitting in the
shelf before it was sold to you. Give US Gypsum a call also and speak to one
of their technical folks. THey are quite helpful and will answer any
quesitons you have pertaining to their product (if that is where your
plaster comes from.)
Hope this helps
Craig Dunn Clark
619 East 11 1/2 st
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org
----- Original Message -----
From: "lili krakowski"
To:
Sent: Friday, February 27, 2004 7:37 AM
Subject: plaster help please
I know very little about plaster, and need help.
In September I bought some moulding plaster, used half the bag, wrapped the
rest tightly in its own bag and put in a bucket. Bucket stored in a shed
that is dry but totally unheated--i.e. it is below freezing in there a lot.
Reopened bag just now, made a sample batch (very small)
The plaster is granular, sort of like pie crust when one has just cut the
shortening in, something like cornmeal except uneven.
Is there any sense using it for a mold for my tiny bricks? Would sieving do
anything except make a mess? Would bringing the dry plaster to room temp do
anything?
Is a totally sealed bag of plaster bought at same time have a chance of
being "good"?
Many thanks
Lili Krakowski
Be of good courage
____________________________________________________________________________
__
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Kathy Forer on fri 27 feb 04
It's best to store plaster wrapped or better, double-wrapped, in
plastic in an airtight covered bucket or container. Otherwise moisture
from freezing and thawing will get inside even when it's dry.
Kathy
John Rodgers on fri 27 feb 04
Lily, the usefulness of this plaster is gone. Toss it. Bite the bullet
and buy a new bag. When you open the bag test it to see if the plaster
is fine, powder like and free of nodules. If so, it is a good bag. That
portion that you don't use, put in a heavy, double [plastic bag, squeeze
out all air, wrap it tight, and put in a relatively airtight box plastic
box. it should keep for a reasonable period of time. I woud try and use
it all up in less than 6 months or it may go bad just sitting there.
Regards,
John Rodgers
Chelsea, AL
lili krakowski wrote:
>I know very little about plaster, and need help.
>
>In September I bought some moulding plaster, used half the bag, wrapped the rest tightly in its own bag and put in a bucket. Bucket stored in a shed that is dry but totally unheated--i.e. it is below freezing in there a lot.
>
>Reopened bag just now, made a sample batch (very small)
>The plaster is granular, sort of like pie crust when one has just cut the shortening in, something like cornmeal except uneven.
>
>Is there any sense using it for a mold for my tiny bricks? Would sieving do anything except make a mess? Would bringing the dry plaster to room temp do anything?
>
>Is a totally sealed bag of plaster bought at same time have a chance of being "good"?
>
>Many thanks
>
>
>Lili Krakowski
>
>Be of good courage
>
>______________________________________________________________________________
>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.
>
>
>
Ivor and Olive Lewis on sat 28 feb 04
Dear Lili,
Sad to say, water vapour has the ability to permeate into the best
wrapped of bags.
It seems probable yours has started to react with atmospheric
moisture.
I would test a small sample and see if it sets up well.
I think all forms of plaster, even in unviolated virgin bags has a
limited shelf life.
Best regards,
Ivor Lewis. Redhill, South Australia.
----- Original Message -----
From: "lili krakowski"
To:
Sent: Saturday, 28 February 2004 12:07
Subject: plaster help please
I know very little about plaster, and need help.
In September I bought some moulding plaster, used half the bag,
wrapped the rest tightly in its own bag and put in a bucket. Bucket
stored in a shed that is dry but totally unheated--i.e. it is below
freezing in there a lot.
Reopened bag just now, made a sample batch (very small)
The plaster is granular, sort of like pie crust when one has just cut
the shortening in, something like cornmeal except uneven.
Is there any sense using it for a mold for my tiny bricks? Would
sieving do anything except make a mess? Would bringing the dry
plaster to room temp do anything?
Is a totally sealed bag of plaster bought at same time have a chance
of being "good"?
Many thanks
Lili Krakowski
Be of good courage
______________________________________________________________________
________
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.
Eleanora Eden on thu 11 mar 04
Hi Lili and all,
I read all the posts and happily see all of the points have been
covered. I especially liked that Craig thought to mention asking the
supplier how long the bag was sitting around.
About 15 years ago I was going through alot of plaster and ran out. I had
some sent from a nearby supplier I wasn't familiar with. BAD IDEA. When
it comes to plaster, KNOW YOUR DEALER!!!!! You want to buy from a supplier
that knows how to buy and store plaster. My wonderful main ceramics
supplier, Vermont Ceramics in Rutland, also makes molds and they order in
small batches and keep it dry. Also they buy it in 50 lb sacks!!!! I
think you should never let somebody sell you a 100 lb sack of plaster. It
is just making everything more difficult.
As soon as I get it home I put each unopened bag in a heavy garbage sack
and wrap and tape it. Store it on a wooden platform, in a dry area, never
on the cement floor. With all of this, I have had very good experience and
can go into a bag after 6 months and it is fine. Better to just buy one
sack at a time if you don't have experience storing it.
Best, Eleanora
At 08:37 AM 2/27/04 -0500, you wrote:
>I know very little about plaster, and need help.
>
>In September I bought some moulding plaster, used half the bag, wrapped
>the rest tightly in its own bag and put in a bucket. Bucket stored in a
>shed that is dry but totally unheated--i.e. it is below freezing in there
>a lot.
>
>Reopened bag just now, made a sample batch (very small)
>The plaster is granular, sort of like pie crust when one has just cut the
>shortening in, something like cornmeal except uneven.
>
>Is there any sense using it for a mold for my tiny bricks? Would sieving
>do anything except make a mess? Would bringing the dry plaster to room
>temp do anything?
>
>Is a totally sealed bag of plaster bought at same time have a chance of
>being "good"?
>
>Many thanks
>
>
>Lili Krakowski
>
>Be of good courage
>
>______________________________________________________________________________
>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.
Eleanora Eden 802 869-2003
Paradise Hill Road eeden@vermontel.net
Bellows Falls, VT 05101 www.eleanoraeden.com
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