Is finishing plaster always pink?

[Cursitor Doom]

Hi guys,

I've ripped out the old bath and had another nasty surprise. It seems some clot may have used Multifinish instead of one-coat or Bonding at a depth of about 3/4" straight onto brickwork. I'm guessing this is what's happened, because this plaster has a definite pink tint to it. I need to increase the depth of this plaster to around one inch, but am reluctant to go over the existing plaster as I fear it will be a very poor 'foundation' as it were. How can I tell for sure if the builder/bodger misused a finish plaster on this brickwork? Is there a simple way to tell?

cheers,

cd

[mike]

Bonding / browning can be grey or pink (take a look at the descriptions here):

If someone has used multi finish but it's solidly attached, I wouldn't worry - just PVA it and carry on as normal.

[harryagain]

The colour of plaster (all grades) depends on the source of the gypsum it was made with.

If finishing plaster is used too thickly, giant cracks appear on the surface, if there are no cracks then this hasn't happened. As long as it doesn't sound hllow when tapped, it will be OK.

The norm is to level a rough wall with sand/cement mix and to finish it with plaster. There was/is a plaster for rough filling in called "browning", doesn't seem popular these days due to expense I imagine. It was much lighter to handle than sand & cement mix. I think it has vermiculite in it.

[Andrew Gabriel]

Plaster is made from gypsum. Pure gypsum is white, but is not normally used for making building plaster. Normally gray or pink is used in the UK, depending which quary it came from (and it's the same for bonding, browning, and finish coat).

Finish coat shrinks considerably as it sets - if it's been used more than a few mm thick, it will be riddled with deep cracks which formed as it set (although that could then have been properly skimmed over).

The important thing when plastering over is to be sure the existing base it sound, and will remain sound with the extra weight, and temporary dampness whilst the new plaster dries. You will need to PVA the existing surface as is normal for any reskim.

[Cursitor Doom]

Many thanks, gentlemen. I think that covers it. It's perfectly smooth so that looks promising. I'll test if first for proper adhesion and PVA it as suggested, cheers. :)

[Rick Hughes]

awful lot of make up with plaster. normally rough that out with 4:1 scratch coat first.