Finishing Plaster drying far too quickly.

FD

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I'm patching a wall in my Dad's kitchen after installing conduit drops and will be tiling over the plaster

Yesterday I plastered one of the walls with Blue Hawk Undercoat Plaster then Blue Hawk Finishing Plaster. Had no problems despite using a bag of plaster which has been open and sitting in the bunker for a few years.

This evening I abraded down that wall, cleaned up and started on another wall. I disn;t have enouh in the opened bag so opened a new bag of Finishing Plaster, same make 12.5kg bag, mixed with water the same way I did yesterday which was as per instructions. Bag was still airtight.. As I was applying it, over wet undercoat Plaster I noticed it was setting very quickly. At that juncture, just minutes from mixing, the finishing plaster in the tub was almost solid.

Is there something I am doing wrong? Maybe I opened the hot tap instead of the cold?

By the time I get a new bag of plaster the undercoat / bond coat or whatever it's called will be set and dry. Is that going to pose a problem for applying a good finishing coat?

Will I need to redo both coats?
 
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The plaster is off, bin it and get another bag.

pva the undercoat before applying the finish and it will be ok.
 
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if you live in an area with clay soil, break up the plaster and put it on the garden. Gypsum improves heavy soil and lightens the texture.

True.
 

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Soil is good, not clay like at all but I'll certainly use it in the garden. Thanks for the suggestion .
Odd thing is the bag that was already opened for a few years was lumpy but applied well and has a solid finish.
The plaster that was powder as one would expect plaster to be was the one that set too quickly.
Strange.
I knew I was pushing my luck using plaster a few years old'. Didn't fancy two bus rides each way to dodge city.

BTW, talking of gypsum what's the difference between brown plasters and white?
 
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BTW, talking of gypsum what's the difference between brown plasters and white?
None, it just depends where the gypsum is mined.

Dilute the PVA or neat?
Diluted around 1:3 PVA/water.

Leave to dry?
Apply 2 coats, leave the first coat to dry, apply a 2nd coat & strt plastering as soon as it goes tacky. If the 2nd coat of PVA is sucked straight into raw plaster you’ve already applied, leave the second coat to dry for much longer & then apply a 3rd coat & plaster when tacky; never plaster over dry PVA.

Never risk using out of date plaster or even plaster close to date this time of year & if it’s been opened, forget it; it’ll cause you nothing but grief.

Prime the bare plaster with an acrylic primer before tiling; if using powder adhesive you must prime all gypsum plaster or plasterboard surfaces.
 

FD

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BTW, talking of gypsum what's the difference between brown plasters and white?
None, it just depends where the gypsum is mined.

Dilute the PVA or neat?
Diluted around 1:3 PVA/water.

Leave to dry?
Apply 2 coats, leave the first coat to dry, apply a 2nd coat & strt plastering as soon as it goes tacky. If the 2nd coat of PVA is sucked straight into raw plaster you’ve already applied, leave the second coat to dry for much longer & then apply a 3rd coat & plaster when tacky; never plaster over dry PVA.

Never risk using out of date plaster or even plaster close to date this time of year & if it’s been opened, forget it; it’ll cause you nothing but grief.

Prime the bare plaster with an acrylic primer before tiling; if using powder adhesive you must prime all gypsum plaster or plasterboard surfaces.

Thanks Richard, Alastair and John.
I bought new bonding, finishing & PVA etc today, hacked out the bodge up I did a couple of night ago and away to start again.
 
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I'd never waste my money on small "very expensive" bags of Blue Hawk plaster,,, £6 to £7 odd for a "12.5kg" bag of plaster,,, :rolleyes: a rip of in my opinion. I've never bought it. You'll never get a tradesman buying that stuff either, unless he's really desperate,, maybe not even then. It's made for the DIY market,, people who don't really know what other materials are available. Buy British Gypsum plasters/products, and you're buying the best at reasonable prices.
 

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Yes, I know it cheaper, there's higher turnover and a better branded product in a builders' merchant but there's no way I can carry 2 bloody 25kg bags home on 2 buses.
The Blue Hawk has done a very good job before.
 
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