# Forum Home Renovation Rendering  PH level in white set plaster?

## Nestingmum

I have some new white set plaster walls to paint, but I'm a little confused. I have been told all along that it's the moisture content that matters. They were done about 3 months ago in the height of summer, so I'm sure they're well and truly dry, the guy in the paint shop told me just to paint with an oilbased sealer and I'll be right. But i had a chat with a chap in the 'mighty helpful' store, who told me it's all about the PH level, more so than the moisture level. He gave me a sample of this blue liquid that I can splash on a section and if the PH level isn't ready and it bubbles it's still "hot" and not ready to paint and they usually recommend people wait 6 -12 months to paint, but if I absolutely HAD to paint now I could paint on a layer of this blue stuff which levels out the PH'ness and I could then use a water based undercoat, whereas the paint store guy said it should be fine now to use the oilbased sealer with no mention of PH levels.  
I've read several conflicting threads on this here about white set plaster but with no mention of PH levels, anymore light to shed on this anyone?? 
Thanks :Smilie:

----------


## Bloss

Is this 'white set plaster' over brick or blockwork or are you referring to the jointing plaster in plasterboard walls? 
In any case if has been in place for 3 mths then a water-based acrylic sealer/undercoat will work fine then two or three coats of the final finish. 
Go to any number of paint manufacturers' web sites and see if they mention PH levels of dry plaster - and you won't find any! A furphy if ever there were one. 
Trying to paint over while wet/ not fully dry, or using a PVA or other paint rather than a sealer/undercoat made for the purpose can be problematic, but PH level - new one to me.

----------


## Nestingmum

It's new plaster over double brick walls. Yes I haven't had any luck finding anymore info on this either, but why would this guy give me this info if it's not relevant? Seems like a bit of an elaborate way of selling a different product. It's a new house so settling cracks are another reason for putting it off a bit, so I think we will anyway, and it'll be easier to choose colour while we're living in the house.  
Thanks oldboss

----------


## Bloss

When you find out why salespeople so often talk rubbish and tell porkies then tell the world - too many just do . . .    :Biggrin:

----------


## prof_montoya

I had a similar issue to yours (similar - I had my walls skimmed with white set - only couple of mm).  I contacted various paint manufactures inquiring about undercoat as I believe the walls have to breath to let moisture out.  Oil based paint seals in moisture. Water based paint breaths.  Problem was that water based paint is affected by pH. In one case I spoke with a paint manufacturers chemists and they also mentioned pH.  I think it was someone from Solver. Try giving them a call.

----------


## Bloss

Probably helps to look at the thread start date  :2thumbsup:  - I reckon he's painted it by now.   :Biggrin:  
In any case google is your friend - show us the link to the paint manufacturers that refers to this problem and I might be convinced it exists.

----------

