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Can Dead Plaster Be Revived? (Call The Paramedics!)


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i know plaster dies at 6 months.  i do not know why.  i have called USGypsum to ask their technical person if calcining it or heating it or anything can be done so i can use some old plaster.  maybe it is anhydrous and takes water vapor from the atmosphere and that is what kills it.

 

after going round and round with phone numbers and recordings i pressed 4 to reach the person who knows "hobby plaster".  a very nice sounding recorded voice advised me that he had retired and could not be reached any more.  he gave me a different number.  suffice it to say i went round and round for over 20 more minutes, never reaching anyone who knows about plaster.

 

the very nice young lady i kept circling back to was very apologetic but did not see any reason to change the message from the man who retired "about a year ago".  she was sure a salesman would be able to answer any question i have.  really................

 

this sounds like a nerd question, i hope he is here.

 

of course, i could go to my "local" supplier and buy a new bag.  it is 65 miles in any direction to reach a supplier.  i have half a bag of several years old plaster.  anyone know how and if it can be revived?  i will toss it if necessary.  is it good in a garden?

 

i do not want to use it to make a small mold in the state it is in

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OldLady I had 2 year old #1 Pottery Plaster. I started making plaster bats using the Lester Bat system. The bat instructions said use 1800 g of plaster and 1200 g of water. That did not work out so well. Reduced the water to 1100 g. This worked but instead of waiting 45 minutes before removing from the mold, had to wait 1 hour and 30 minutes. It all worked nicely and I have some nice plaster bats.

 

If you have ever been in MS then you know of the humidity we have - does not get less than 50%.

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https://books.google.co.uk/books?id=gDngCgAAQBAJ&pg=PA294&lpg=PA294&dq=make+plaster+anhydrous+again&source=bl&ots=QV4n82HRGt&sig=TWLMSNkh8LQ5EoDr6Xw_8Y9iF6Y&hl=en&sa=X&ved=0ahUKEwjdtuSk4fjMAhUJLcAKHS0NAkUQ6AEIIjAB#v=onepage&q=make%20plaster%20anhydrous%20again&f=false

 

This seems to say 260c will do it, wiki said 130c would do it. My initial thoughts were 800c where clay loses the chemical water. Who knows but it is possible, not sure if it would be as fine a powder after the process and work as well.

 

After reading that book more it seems to explain it all.

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No there is no way to make plaster exposed to humidity better.This is a true fact

I used to work for USGypsum as their hobby plaster expert and have since retired to play with clay as a full time production potter

For years I talked people off the cliff as they tried to bake plaster in their home ovens or tried to BBQ it on the grill with their pit fired stuff.

The fact is once you open the bag you have to protect the contents from air. You can use a vacuum sealer or double bag it then put in sealed container and pray

or keep it in very warm dry space or the vacuum of deep space whichever you have access to.Since you live part of the year in Florida you could ask your Nasa friends to send up a partial bag  on next space X test flight until needed.If you have migrated north and are on the east coast where humidity is king I suggest tossing the bag out. Plaster makes a good soil amendment as well.

My experience of sieving the lumps is no cure either as the plaster is now weaker and water and set times are now just a guess. So throwing bats is a good solution for old stuff-molds are out as its not worth the effort. Sixty five miles is a drop in the hat-get two bags and do not open the second one.Wrap that second one in two sealed plastic bags and keep in warm dry space until needed.

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Grating in a small amount of cured plaster will act as a catalyst. This helps set the older plaster quickly.

 

As Mark said, use it for relatively unimportant shapes like wedging tables, plaster bats, damp cupboard bases, or simple slump molds.

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thank you mark, i knew that would be the case but just can't believe it is really dead.  even though  it does look a little pasty white and unhealthy.  

 

and just FYI, driving 65 miles in northern california is not the same as 65 miles in the washington dc, baltimore area.    it is more like driving in LA.

 

joel, the page is not viewable, unfortunately.  would like to see it.

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 (northern california is not the same as 65 miles in the washington dc, baltimore area)

 

You got to move for sure now-who needs all those people and traffic.

I can formulate a list of reasons to head to the hills if you need one.

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Probably something to do with different laws in UK or something.

 

The important parts. "If powdered gypsum is heated to approximate 170c it loses three-quarters of its water of crystallisation and becomes class A plaster knows as plaster of paris...""If the powdered gypsum is heated to 260c it loses nearly all its combined water and becomes Anhydrous Gypsum Plaster(class c plaster), known as Siraphite plaster. Approx 1% alum or zinc is added to accelerate the set...""A harder plaster may be produced by heating the powdered gypsum to a temperature of 370c. This produces a superheated anhydrous gypsum plaster (class d plaster), knows as keene's cement..."

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thank you, Joel and John. because i want to make a permanent mold,  i will get some new plaster the next time i go to Baltimore.  it is a great trip, 65 miles from bucolic to bedlam and the return 65 miles is a joy.  in between i am in a city.  one with lots of attractions.  i always wind up down by the water surrounded by tall buildings.  a total 180 degrees from my peaceful studio on the river.

 

meantime, i will heat a smaller amount in my oven and make some smaller stamps.

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{snip}  i will get some new plaster the next time i go to Baltimore. {endsnip}

Hey there oldlady and sorta-neighbor. Do you know that Clayworks Supplies up in Bawlamer (as we who are from there pronounce it, though I don't live there anymore but still tawk like it sometimes...) now has a second store in Alexandria VA, just off the exit of I495 (beltway) and I395? 5704-C General Washington Dr, Alex. 22312, ph. 703.256.7500. Not nearly the bedlam of Falls Rd. in Balto, but then you won't get to smell the horses at Pimlico either (or the Inner Harbor)...    Let us know if you come this way and we'll have welcoming party for you.

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dick, ha hun,  (translation "hi, honey."  nobody in bawlamer needs to remember anyone's name.)    i thought that place closed years ago.  it had studio space to share and lots of potters used it.  is it in the same place?  

 

a trip to alexandria  ends up at the torpedo factory.  always wanted to get into that place, even when it was brand new and the ladies room had a radiator hanging on the wall that burned my leg every time i went in there.  before the big remodel, and after the remodel.  was in the kiln club for several years but they don't want me anymore, i live too far away.

 

i was told my stuff was too commercial and i would not need the torpedo factory to sell it because it was intended for artists.

 

why can't people just say "go away, we don't like your stuff"."

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dick, ha hun,  (translation "hi, honey."  nobody in bawlamer needs to remember anyone's name.)    i thought that place closed years ago.  it had studio space to share and lots of potters used it.  is it in the same place?  

 

a trip to alexandria  ends up at the torpedo factory.  always wanted to get into that place, even when it was brand new and the ladies room had a radiator hanging on the wall that burned my leg every time i went in there.  before the big remodel, and after the remodel.  was in the kiln club for several years but they don't want me anymore, i live too far away.

 

i was told my stuff was too commercial and i would not need the torpedo factory to sell it because it was intended for artists.

 

why can't people just say "go away, we don't like your stuff"."

The old Creative Clay studio closed a couple years ago; some of the folks associated with it -- including Dick -- set up a new shop called Alexandria Clay Coop. Before the old studio closed (collapsed or your choice of adjective), it dropped its supplies side-line and Baltimore Clayworks Supplies opened up shop next to it (a long story behind that move). Anyhow, Clayworks is still there while the old studio is history.

 

Will avoid any comments on the Torpedo Factory.

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This has been a great thread!!!  Makes me want to head east for a visit!!  But my hand is up with a question.  I bought plaster of paris at the hardware store to make some damp boxes. It worked great.  Love those boxes!!  Should I have used a better grade of plaster?

 

Roberta

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This has been a great thread!!!  Makes me want to head east for a visit!!  But my hand is up with a question.  I bought plaster of paris at the hardware store to make some damp boxes. It worked great.  Love those boxes!!  Should I have used a better grade of plaster?

 

Roberta

If it works, it works. I have found the plaster from my pottery supply store to be less expensive -- but you have to buy a 50 lb bag; plaster of paris comes in smaller bags at the hardware and building supplies stores.

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Roberta, as Bruce said, it works for that purpose. #1 Pottery Plaster has a harder, smoother surface and is stronger than Plaster of Paris and thus is preferable for molds and plaster things that need strength and/or surface definition. But Plaster of Paris is fine for a damp box, and is more readily available in smaller quantities.

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Since you already called them-

(Call The Paramedics!)

give that old plaster to them to make casts from.

I never got a straight answer on that Torpedo factory? is it from world war II or just a made up dance club name?

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it was a real factory for making torpedos for world war I.  the building was built to withstand an accidental misfiring and could not be destroyed.  it sat empty for years in the middle of a blighted neighborhood.  an artist and her friends convinced the alexandria city government to let them use it for an arts studio for many different types of artists who had no other space to work.  that was just before 1976 and the results are fantastic.  you can look up the story online.  i wrote about it here years ago.

 

it is now the center of a thriving area of homes, stores, offices, touristy stuff, and a dock over the river full of restaurants.  i can't apply for membership because they always do their jurying during the winter.  too bad.  

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(i can't apply for membership because they always do their jurying during the winter.  too bad. )

since you are now migrating with the birds how about leaving a box or whatever is needed with a fiend who stays north and can drop and pick up the jury stuff?

Thanks for the history lesson as well. 

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(i can't apply for membership because they always do their jurying during the winter.  too bad. )

since you are now migrating with the birds how about leaving a box or whatever is needed with a fiend who stays north and can drop and pick up the jury stuff?

Torpedo Factory requires their artists to be in their work/show space a certain number of hours each week . . . would make a really rough commute for Old Lady from Florida (or West Virginia). Many of the old timers take on associates who sit in the shop in return for space to display wares, allowing them to do the winter migrations or work at home. I've been told the jury process is rather, er . . . political. The center and its business model is being evaluated by the city which leases the space to the artists and the media around here have done recent articles on management/operations problems.

 

http://torpedofactory.org/

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