Decorating clues sought

[Tim Streater]

The porch being built on the side of our house is now ready to be painted. It connects into the Utility Room of the house, and was made big enough to house the washer/dryer. Plastering was finished yesterday, and the builder is now on hols for about 10 days. We may or may not get the plumber and sparks in next week to do a bit more.

So - we have new, drying, plaster in the porch, and some old, unpainted plaster in the utility room. I'm told we should size the plaster before painting once it's dry, and then two coats of emulsion.

1) How long should we wait for the new plaster to dry? Builder seemed to imply that once it went pale from dark pink, it could be worked on. Elsewhere I've heard a figure of four weeks, seems excessive.

2) What should we size it with? "Diluted emulsion" has been mentioned - diluted to what strength, or is this a bad idea and I should use something designed for the job?

[Dean Heighington]

it's known to me as a miss/ mist coat-

50/50 water and emulsion. You can use a cheap emulsion and maybe less water as you will get covered in it!

This can usually be applied a day or two after plastering, depending on conditions- if dark patches are shrinking to isolated spots, your nearly there... just give it another day.

Don't be fussy with the mist coat, just get it on and leave streaks- you're giving it a wash coat, not applying a layer of paint.

Hopefully ur plasterer hasn't trowelled the finish up too shiny, this makes their work look mint but is a bugger to paint:)

Hth Deano

[stuart noble]

Providing you use a decent emulsion, you shouldn't have to thin it. I don't regard the typical Dulux non-drip cottage cheese as a paint at all. Last time I painted new plaster Crown was a thinner consistency, but actually covered better. IMO the mist coat is a builders' bodge that has somehow gained respectability over the years without making any sense technically. Adding water doesn't "thin" an emulsion in the way that white spirit thins an oil paint

[Tim Streater]

What the builder said was, if you paint bare plaster with straight emulsion, after a week or two it'll just peel off. Something to so with the fact that new bare plaster absorbs moisture, I imagine, and hence the idea of diluting it.

[The Natural Philosopher]

piss coat. :-)

[Dean Heighington]

I disagree. The new plaster sucks all the moisture from paint so using a mist coat helps by having the water sucked then leaving a thin film of the emulsion which will provide a key for the top coats. Every decorator I know, does it. There are other products but if you've got 10+ litres of Gardenia then why not use it. Farrow & ball is by far the best paint IMO.

[Dean Heighington]

Exactly! See my recent post.

[stuart noble]

Try putting a spoonful of paint on a piece of kitchen roll. If you see an outer ring of clear or cloudy water developing as it soaks in, you have a badly formulated paint. A good product should soak into the paper uniformly, and would behave in the same way on plaster. A bit anal I know but I used to be much concerned with these issues in a previous life :-)

[Dean Heighington]

previous life :-)

The house 'boss' has just caught me with one of her spoons in a can of paint. She's not happy :)

[stuart noble]

previous life :-)

If women can stir paint with a bloke's chisels...

[Mr Fuxit]

So use undiluted emulsion on the plaster whilst it's still wet.

[The Medway Handyman]

Get some of the paint they use on DIY SOS. It will go over plaster after 20 mins :-)

[Andy Wade]

Whether or not you call it thinning, Dulux Trade recommend adding water to vinyl matt emulsion as follows:

Sealing new or bare surfaces: Add up to 1 part clean water to 5 parts paint.

Normal use (not to be exceeded): Add up to 1 part clean water to 10 parts paint.

Conventional spray application: Add up to 1 part clean water to 2.5 parts paint.

Airless spray application: Add up to 1 part clean water to 5 parts paint.

(copied from