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Old May 22nd 05, 11:06 AM
Moonshine
 
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Default UnderCoat Plaster shrivels up like biscuit - why?

I've had a couple of goes at doing this with the same failed result.

Just trying to base coat plaster patch over some chased in channeling.

When going back to it in the morning it has all just shriveled up and
cracked like a wholemeal biscuit :-(

I've wet the surface before applying.

The house is warm with CH running - could it be drying out too quick?
Could the mix be too dry?

Am I using the wrong stuff - Blue Hawk Undercoat Plaster (which claims
to be non-shrinking!)?

Thanks

Cliff

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Old May 22nd 05, 11:57 AM
Alan
 
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In message , Moonshine
wrote
I've had a couple of goes at doing this with the same failed result.

Just trying to base coat plaster patch over some chased in channeling.

When going back to it in the morning it has all just shriveled up and
cracked like a wholemeal biscuit :-(

I've wet the surface before applying.

The house is warm with CH running - could it be drying out too quick?
Could the mix be too dry?

Am I using the wrong stuff - Blue Hawk Undercoat Plaster (which claims
to be non-shrinking!)?


Surrounding plaster sucking out all of the water in the new plaster. Try
'painting' the channel with a water/PVA mix to seal the surface - let
that dry - wet down the area and then plaster.

--
Alan

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Old May 22nd 05, 12:52 PM
Dave Liquorice
 
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On Sun, 22 May 2005 10:57:04 +0100, Alan wrote:

Surrounding plaster sucking out all of the water in the new plaster.
Try 'painting' the channel with a water/PVA mix to seal the surface
- let that dry - wet down the area and then plaster.


The orginal mix may well have been be too wet as well. Thick whipped
cream consistancy, just about falls of the trowel when picked up and
the blade turned vertical.

--
Cheers
Dave. pam is missing e-mail



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Old May 22nd 05, 03:41 PM
Moonshine
 
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On Sun, 22 May 2005 11:52:43 +0100 (BST), "Dave Liquorice"
wrote:

On Sun, 22 May 2005 10:57:04 +0100, Alan wrote:

Surrounding plaster sucking out all of the water in the new plaster.
Try 'painting' the channel with a water/PVA mix to seal the surface
- let that dry - wet down the area and then plaster.


The orginal mix may well have been be too wet as well. Thick whipped
cream consistancy, just about falls of the trowel when picked up and
the blade turned vertical.


Cheers Guys,

I've PVA'd it and will give it another go later on.

Cliff
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Old May 22nd 05, 03:49 PM
mark down
 
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On Sun, 22 May 2005 09:06:03 GMT, Moonshine wrote:

I've had a couple of goes at doing this with the same failed result.

Just trying to base coat plaster patch over some chased in channeling.

When going back to it in the morning it has all just shriveled up and
cracked like a wholemeal biscuit :-(

I've wet the surface before applying.

The house is warm with CH running - could it be drying out too quick?
Could the mix be too dry?

Am I using the wrong stuff - Blue Hawk Undercoat Plaster (which claims
to be non-shrinking!)?

Thanks

Cliff

Bonding coat is probably better for small patching to old plaster but
not vital. Bonding coat also shrinks and cracks but for patching that
means you can put the finish coat on and still get it perfectly flush
with the old plastera assuming you ruled off the patch against the
surrounding plaster Just put the finish on and dont worry about the
cracks -they just improve the key.

M


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Old May 22nd 05, 08:52 PM
Mike
 
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"Moonshine" wrote in message
...
I've had a couple of goes at doing this with the same failed result.

Just trying to base coat plaster patch over some chased in channeling.

When going back to it in the morning it has all just shriveled up and
cracked like a wholemeal biscuit :-(

I've wet the surface before applying.

The house is warm with CH running - could it be drying out too quick?
Could the mix be too dry?

Am I using the wrong stuff - Blue Hawk Undercoat Plaster (which claims
to be non-shrinking!)?



British Gypsum Bonding coat would be better (and cheaper) but even that
sometimes cracks on the first coat. Don't put it on too thickly and rush
the job. The second coat will stay smooth.


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Old May 23rd 05, 09:44 AM
Moonshine
 
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On Sun, 22 May 2005 19:52:42 +0100, "Mike" wrote:


"Moonshine" wrote in message
.. .
I've had a couple of goes at doing this with the same failed result.

Just trying to base coat plaster patch over some chased in channeling.

When going back to it in the morning it has all just shriveled up and
cracked like a wholemeal biscuit :-(

I've wet the surface before applying.

The house is warm with CH running - could it be drying out too quick?
Could the mix be too dry?

Am I using the wrong stuff - Blue Hawk Undercoat Plaster (which claims
to be non-shrinking!)?



British Gypsum Bonding coat would be better (and cheaper) but even that
sometimes cracks on the first coat. Don't put it on too thickly and rush
the job. The second coat will stay smooth.


Success - the PVA worked, woke up to non-cracked plaster. It also
appears as has been said that "base coat" is not the right plaster to
use in this high suction application. You live and learn :-) This
stuff seems to have some fine yellow particles in it too - what might
that be?


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