Warren Heintz on tue 28 dec 04
Here is a sure fire method for mixing plaster,excuse me if I repeating something here. Have your container of water ready Allow the water to become still. Start sifting in the plaster and DO NOT stir the water at all. Keep sifting the plaster until an island of plaster floats on the water ,dry This tells you that the water can not hold any more plaster then reach in feel for lumps smashing them, and then stir. It is very important not to stir until the islands form, as it will cause the plaster to float before there is enough plaster. This process works for any amount, but in larger amounts the plaster is really floating where as in smaller amount ,the island is more than likely the top of a pile. Works everytime,just don't stir the water until the islands form,and when they do you can add some more plaster if you like it will just make it set faster.
Craig Clark wrote:Denis, there is a good chance that you did not get a proper mix of
your plaster to begin with. Since you aren't talking about that much
plaster just break it out, mix up another batch and recast. This time,
rather than trying to mix the plaster in place use a five gallon bucket
or large tub and mix it up properly. You can easily mix up that much
plaster by using a jiffy mixer on a nice stout drill motor. Just mix
until the plaster is well creamed, be careful not to entrain air while
you are doing so, and pour the plaster into the form.
It is important to be certain that the proportion of water to
plaster is correct. If it is not then you will end up with a set that is
not very strong......hence the spalling of the surface. According to the
folks at USG the way to do this is to WEIGH your water and plaster. Do
this!!!! It really is EASY!!!!!!! There is a toll free number to call at
USG where you may speak to one of the technical folks who are very
forthcoming with info on the correct method to mix their products,
depending upon your application. Just dial 1-800-487-4431. It won't cost
you any money. They really know what they are talking about!! You may
need to leave them a call back number if they are busy but they will get
back to you within a few hours. At least they did with me on a few
different occassions in the past year. Just get them to talk you through
the procedure. It really isn't very complicated and is easily conveyed
in a quick phone conversation.
If you are still inclined to keep the slab that you have then rather
than trying to continually patch you may take some canvas and cover the
slab. The plaster still serve as a wick for moisture and will be
protected by the canvas from further errosion or abrasion. Just mix up a
small amount of plaster and "skim-coat" the area that has been damaged.
As long as it is clean the plaster should adhere to the slab. Or frame
up a deeper flask around the existing slab and just pour more plaster,
atleast two inches worth, over what you have already cast.
If you call the folks at USG and tell them what you are doing they
may suggest that you use either hydrostone or hydrocal. They are both
much harder than the no. 1 pottery plaster.
Hope this helps
Craig Dunn Clark
619 East 11 1/2 st
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org
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Denis on tue 28 dec 04
I made a plaster wedging table,3"Hx14"Wx24"L,by placing a plastic bag in
the cavity, adding water and then plaster according to measurements I
thought were correct. Trouble is plaster comes up on the clay in spots.
What is the easiest,way to correct this soft plaster, aside from dumping
the whole thing and starting over?
Might add my studio is in a greenhouse open to dampness and intense heat
by turns. An inactive greenhouse, just glass and corrugated plastic around
me.
Denis
Elizabeth Priddy on tue 28 dec 04
if the plaster is good at leaching water but just soft,
you can cover the table with thin cotton and staple it around the outer edges.
It whould work well to work the clay without the hassles of plaster
Denis wrote:
I made a plaster wedging table,3"Hx14"Wx24"L,by placing a plastic bag in
the cavity, adding water and then plaster according to measurements I
thought were correct. Trouble is plaster comes up on the clay in spots.
What is the easiest,way to correct this soft plaster, aside from dumping
the whole thing and starting over?
Elizabeth Priddy
252-504-2622
1273 Hwy 101
Beaufort, NC 28516
http://www.elizabethpriddy.com
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Take Yahoo! Mail with you! Get it on your mobile phone.
Craig Clark on tue 28 dec 04
Denis, there is a good chance that you did not get a proper mix of
your plaster to begin with. Since you aren't talking about that much
plaster just break it out, mix up another batch and recast. This time,
rather than trying to mix the plaster in place use a five gallon bucket
or large tub and mix it up properly. You can easily mix up that much
plaster by using a jiffy mixer on a nice stout drill motor. Just mix
until the plaster is well creamed, be careful not to entrain air while
you are doing so, and pour the plaster into the form.
It is important to be certain that the proportion of water to
plaster is correct. If it is not then you will end up with a set that is
not very strong......hence the spalling of the surface. According to the
folks at USG the way to do this is to WEIGH your water and plaster. Do
this!!!! It really is EASY!!!!!!! There is a toll free number to call at
USG where you may speak to one of the technical folks who are very
forthcoming with info on the correct method to mix their products,
depending upon your application. Just dial 1-800-487-4431. It won't cost
you any money. They really know what they are talking about!! You may
need to leave them a call back number if they are busy but they will get
back to you within a few hours. At least they did with me on a few
different occassions in the past year. Just get them to talk you through
the procedure. It really isn't very complicated and is easily conveyed
in a quick phone conversation.
If you are still inclined to keep the slab that you have then rather
than trying to continually patch you may take some canvas and cover the
slab. The plaster still serve as a wick for moisture and will be
protected by the canvas from further errosion or abrasion. Just mix up a
small amount of plaster and "skim-coat" the area that has been damaged.
As long as it is clean the plaster should adhere to the slab. Or frame
up a deeper flask around the existing slab and just pour more plaster,
atleast two inches worth, over what you have already cast.
If you call the folks at USG and tell them what you are doing they
may suggest that you use either hydrostone or hydrocal. They are both
much harder than the no. 1 pottery plaster.
Hope this helps
Craig Dunn Clark
619 East 11 1/2 st
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org
>
>______________________________________________________________________________
>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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