Help with plaster patch up

[tireetim]

I am trying to patch up a bit of plaster that had got damaged but a leak from above which has now been fixed (dry for a couple of months). It was originally lime render but I have patched with sand and cement (5:1) with a plasticiser and was going to skim the whole wall after. My question is why has the sand / cement gone a sort of white colour as it's drying (see images)? Is this salts from the wall or something else and will it be a problem? It has set fine. Can I just pva and skim?

Untitled

• tireetim
• 14 Nov 2013
• 2

Untitled

• tireetim
• 14 Nov 2013
• 2

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[roughcaster]

Cement scratch/render will dry out that colour, not a problem. Before you skim, i'd flatten off the scratched areas a bit, let it set, then pva and skim.

 

[Reeves2k2]

Cement scratch/render will dry out that colour, not a problem. Before you skim, i'd flatten off the scratched areas a bit, let it set, then pva and skim.

As the man says, that's normal but personally wouldn't have scratched it before skim

 

[tireetim]

Thanks roughcaster and reeves.
Now it's drying properly it has gone uniform grey and looks more normal. I wasn't sure about scratching it or not - wouldn't do it next time.
Roughcaster - what do you mean by flatten the scratch areas? Go over again with sand and cement and smooth it off ?

 

[roughcaster]

Go over the scratched area with a bit of bonding coat or similar, nothing fancy, just enough to fill up the deeper scratches. Let it go off, then you're ready then to PVA and skim the wall. Skim onto the pva while it's wet/tacky.
For PVA ing onto light coloured surfaces, I always add a drop of red food colouring/dye into the container, enough to turn the pva light pink, so you can see where you are,, and it doesn't stain the finished plaster either.

 

[tireetim]

Great advice - thanks.

 

[roughcaster]

Good luck with your job Tim.