Shelf life of plaster

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A book I have (Renovating Old Houses by George Nash) noted as an aside in one sentence that plaster will only stay usable for around a year. I just bought 100 lb. of plaster (50 lb. USG Struct-o-lite and 50 lb. USG Diamond Veneer Finish plaster) and wonder if it will last longer if I store it in air-tight containers and store in a cool location. When I bought these last week I had no idea it wouldn't keep indefinitely. I have a lot of plaster work to do, but may well not get around to 95% of it for a year or longer. Anyone have experience with these things? Thanks for any info.
Dan
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Dan_Musicant writes:

Plaster will strike in the bag due to infiltration of humidity. It will still be a powder that mixes up OK, but given enough storage time and humidity before use it will have a final strength of a Ritz cracker.
I would think the cost of proper containers would approach the cost of the plaster.
Most cost effective would be 5-gallon paint buckets with the O-ring lids, with a sock full of calcium chloride as a dessicant.
Easy enough to do your own "lab" testing later to verify setting quality. Make some cylindrical samples (cast in a pill bottle) now and when you plan to use it. See if you find any difference in strength or setting time. Better than wasting a lot of labor on material that turns out to be flawed.
Steady non-condensing relative humidity is more important than cool. Warmer may make your RH lower.
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wrote:
:Dan_Musicant writes: : :> wonder if it will last longer if I :> store it in air-tight containers and store in a cool location.: :Plaster will strike in the bag due to infiltration of humidity. It will :still be a powder that mixes up OK, but given enough storage time and :humidity before use it will have a final strength of a Ritz cracker. : :I would think the cost of proper containers would approach the cost of the :plaster. : :Most cost effective would be 5-gallon paint buckets with the O-ring lids, :with a sock full of calcium chloride as a dessicant. : :Easy enough to do your own "lab" testing later to verify setting quality. :Make some cylindrical samples (cast in a pill bottle) now and when you plan :to use it. See if you find any difference in strength or setting time. :Better than wasting a lot of labor on material that turns out to be flawed. : :Steady non-condensing relative humidity is more important than cool. :Warmer may make your RH lower.
Thanks for the post. I cut open the bags last week and put the plasters in plastic bags, fairly thick ones mostly. But I got the idea shortly thereafter to use some plastic buckets I have. These aren't 5 gallon buckets but food service buckets I got from a fast food place. They gave them to me free. They had 10 lb. potato salad in them and I got them with the tops. I have 13 of them now, and can get an unlimited supply in the future for free (I made an arrangement with another source.
I presume they will be air tight, but I think your admonisions are advisable - dessicant and testing. I would never have thought of the dessicant, and I wouldn't have done the testing without your suggestion. However, like you say, it's really important that I not invest time and materials into repairs that turn out to be crap.
Great ideas with the old pill bottles. I have a bunch of them, been saving them for some good use, and this is sure one. Thanks again.
Dan
PS: Anyone know where I can get calcium chloride in quantity economically? Thanks!
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snipped-for-privacy@privacy.net says...
<snip>

Nice. I buy them at the BORG. Free is better. ;-)

Not to mention the work to tear out crap.

It is a good idea. I may have a little grout and thinset to do this with.

The better sidewalk/driveway ice melter is calcium chloride (read the container, NaCl isn't a desicant). You should be able to find it for $12is for a 50lb bag at the BORG or a bit more at a hardware store. It's also available (for a lot more $$) at grocery stores in the winter (too soon now :-( ).
--
Keith

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wrote:
: snipped-for-privacy@privacy.net says... : :<snip> : :> Thanks for the post. I cut open the bags last week and put the plasters :> in plastic bags, fairly thick ones mostly. But I got the idea shortly :> thereafter to use some plastic buckets I have. These aren't 5 gallon :> buckets but food service buckets I got from a fast food place. They gave :> them to me free. They had 10 lb. potato salad in them and I got them :> with the tops. I have 13 of them now, and can get an unlimited supply in :> the future for free (I made an arrangement with another source.: :Nice. I buy them at the BORG. Free is better. ;-) : :> I presume they will be air tight, but I think your admonisions are :> advisable - dessicant and testing. I would never have thought of the :> dessicant, and I wouldn't have done the testing without your suggestion. :> However, like you say, it's really important that I not invest time and :> materials into repairs that turn out to be crap.: :Not to mention the work to tear out crap. : :> Great ideas with the old pill bottles. I have a bunch of them, been :> saving them for some good use, and this is sure one. Thanks again.: :It is a good idea. I may have a little grout and thinset to do :this with. : :> PS: Anyone know where I can get calcium chloride in quantity :> economically? Thanks!: :The better sidewalk/driveway ice melter is calcium chloride (read :the container, NaCl isn't a desicant). You should be able to find :it for $12is for a 50lb bag at the BORG or a bit more at a hardware :store. It's also available (for a lot more $$) at grocery stores :in the winter (too soon now :-( ).
What is the BORG? I'm in Berkeley, CA. A Google search on BORG doesn't seem to come up with anything. Is it like Lowe's and Home Depot? Thanks.
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wrote:
[snip]

We are the Borg. You will be assimilated. Resistance is futile.
But what if we don't want to be assimilated?
That is irrelevant. You are irrelevant. You will be assimilated.
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Dan_Musicant wrote:

Big Orange Retail Giant = Home Depot
a guess.
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Dan_Musicant writes:

Polyethylene bags are poor vapor barriers.

Swimming pool store.
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wrote:
:Dan_Musicant writes: : :> I cut open the bags last week and put the plasters :> in plastic bags, fairly thick ones mostly.: :Polyethylene bags are poor vapor barriers.
Thanks. : :> Anyone know where I can get calcium chloride in quantity :> economically?: :Swimming pool store.
Thank you. It doesn't snow here, so swimming pool water conditioner is easier had than snow melter.
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wrote:
:Most cost effective would be 5-gallon paint buckets with the O-ring lids, :with a sock full of calcium chloride as a dessicant. A pool supply place I'm talking to doesn't have it but they stock calcium hypochlorite, which he says is a "pool shocker" or some such thing. Is that a dessicant (i.e. OK) or do I want calcium chloride? TIA
Dan
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No.
In my experience, an air-tight container is sufficient. No need for a dessicant.
--
Regards,
Doug Miller (alphageek at milmac dot com)
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On Tue, 05 Sep 2006 18:39:50 GMT, snipped-for-privacy@milmac.com (Doug Miller) wrote:
:> :>:Most cost effective would be 5-gallon paint buckets with the O-ring lids, :>:with a sock full of calcium chloride as a dessicant. :>A pool supply place I'm talking to doesn't have it but they stock :>calcium hypochlorite, which he says is a "pool shocker" or some such :>thing. Is that a dessicant (i.e. OK): :No. : :> or do I want calcium chloride? TIA: :In my experience, an air-tight container is sufficient. No need for a :dessicant.
The problem is that I'm uncertain if these containers will indeed be air tight or not. I think they may be absolutely air tight, but I'd hate to find out they aren't by having my plaster go bad, especially if I've gone ahead and used it. I'll try to find a cheap source of calcium chloride.
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experience, putting it in an airtight container is enough. How hard is it to find an airtight container? All I'm using is a five-gallon bucket and lid that I bought at Lowe's for about $8, and it works _just_fine_. No dessicants. No driers. Just a tight lid.
--
Regards,
Doug Miller (alphageek at milmac dot com)
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On Wed, 06 Sep 2006 19:15:30 GMT, snipped-for-privacy@milmac.com (Doug Miller) wrote:
:>The problem is that I'm uncertain if these containers will indeed be air :>tight or not. I think they may be absolutely air tight, but I'd hate to :>find out they aren't by having my plaster go bad, especially if I've :>gone ahead and used it. I'll try to find a cheap source of calcium:>chloride. :> :Haven't you been reading my posts? I've said at least twice that in my own :experience, putting it in an airtight container is enough. How hard is it to :find an airtight container? All I'm using is a five-gallon bucket and lid that :I bought at Lowe's for about $8, and it works _just_fine_. No dessicants. :No driers. Just a tight lid.
It's hard for me to be certain that my containers are tight. I better do something soon, though, because I have the plaster in my garage and the rainy season is around the corner. On top of that, my garage needs a new roof! I'm gonna be a busy guy.
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and buy the damn bucket and lid already. It'll be tight enough to keep your plaster from going bad. Worked for me over a period of several years.
--
Regards,
Doug Miller (alphageek at milmac dot com)
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Dan_Musicant writes:

Putting a dessicant in a leaky or permeable container just lengthens the time the interior stays dry. Eventually the dessicant saturates and becomes inert. In the case of a deliquescent like calcium chloride, it turns into a nasty, corrosive goo. Thus the advantages to silica gel or molecular sieves.
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wrote:
:Dan_Musicant writes: : :> The problem is that I'm uncertain if these containers will indeed be air :> tight or not.: :Putting a dessicant in a leaky or permeable container just lengthens the :time the interior stays dry. Eventually the dessicant saturates and :becomes inert. In the case of a deliquescent like calcium chloride, it :turns into a nasty, corrosive goo. Thus the advantages to silica gel or :molecular sieves.
I've spent an hour or two trying to locate CaCl2 hereabouts, but not done well. The pool supply places say they don't carry it and most are a ways from me, anyway.
Chemical supply places are too expensive. I did find one that will sell me 50 lb. for around $55 including tax, so that's a possibility. But 50 lb. seems like a lot and I'll have to store IT somehow so it stays dry!! Pretty funny, in a way. I found some on eBay, 5 lb. for around $22 shipped. Maybe I'll do that. The CaCl2 is $10, the shipping $12. Or 10 lb. for around $32. I guess if I can keep it dry, it might be a good investment.
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Dan_Musicant writes:

That's odd. It is a necessary ingredient to protect any plaster pool surface from soft-water etching. Maybe the pool supply places are in the replastering business, too.
Another source is concrete suppliers, where it is used as an accelerant.
I would also ask at an Agway feed store type place.
Or just the 42 oz DampRid refill at Home Depot.
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wrote:
:Dan_Musicant writes: : :> The pool supply places say they don't carry it ...: :That's odd. It is a necessary ingredient to protect any plaster pool :surface from soft-water etching. Maybe the pool supply places are in the :replastering business, too. : :Another source is concrete suppliers, where it is used as an accelerant. : :I would also ask at an Agway feed store type place. : :Or just the 42 oz DampRid refill at Home Depot. I called HD, but they couldn't find it. Orchard Supply tells me they have calcium chloride in 26 oz. packages for $3.99. I think I may get a couple of those. Cheaper and faster than eBay.
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wrote:

rice is pretty hygroscopic.
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