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
In message , Moonshine 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
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
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?
Base coat is an application, not a particular sort of plaster.
perlite/vermiculite?
SAND
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