Mist coat washes off with a wet sponge

[jacoscar]

I had my living room plastered 6 months ago, so it’s well dry

I applied this as a mist coat

Wickes Matt Emulsion Paint - White - 10L | Wickes.co.uk

Wickes Matt Emulsion Paint - White - 10L

www.wickes.co.uk

3 part paint and 1 part water
That’s 25% dilution, even though the bucket says I could go up to 40%

I just tried to brush the wall with a wet sponge and this happened (the coat was applied 4 days ago), is this normal?

It basically got back to bare plaster

 

[DiyNutJob]

If you reduce the sticking power of paint by 75%, seems logical it won't stick well. I know nothing about mist coating. But I am happy to guess it's done to clear out dust or powder that would interfere with paint adhesion. It could be done with plain water, then you wouldn't be able to tell which part is done and which part isn't if the process is interrupted for a period of time long enough for the water to dry.

 

[mattylad]

I'd have thought that by adding 25% water the paint is only reduced by 25% not 75%???

Yes 4 days is not long enough.

 

[DiyNutJob]

I'd have thought that by adding 25% water the paint is only reduced by 25% not 75%???

Yes 4 days is not long enough.

I misread. 25% dilution is not much of a mist coat then. In that case, I am guessing the powder residuals from manufacturing resulted in non-adhesion.

 

[jacoscar]

I misread. 25% dilution is not much of a mist coat then. In that case, I am guessing the powder residuals from manufacturing resulted in non-adhesion.

I had asked a similar question a few months ago where I had diluted at 40% and I was told it was too much water
Now it’s too little water

However, I am not clear if the mist coat is supposed to be washable with a wet sponge

 

[Mottie]

I always thought it was 50/50?

 

[jacoscar]

I always thought it was 50/50?

The instruction on the bucket say up to 40% water 60% paint

 

[Mottie]

How about this then? Special offer - £2!

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[RandomGrinch]

. I know nothing about mist coating. But I am happy to guess it's done to clear out dust or powder that would interfere with paint adhesion

Close but not quite!
New plaster is like a sponge, it sucks moisture in like crazy - it's why you really have to move fast when plastering and put on the next coat at just the right moment.

If you put paint on new plaster without the mist, it will literally suck the moisture out of the paint, leaving a skin of pigment on the surface that can be scraped off in sheets.

I've used 50/50 mist coats and multiple mist coats without issue. One thing to note, in this current heat, what may start as a 50/50 will be a good deal less sloppy when you finish!

I've also used the new plaster sealant, which is great stuff, but expensive.
I tend to save it for areas where I've used a lot of filler; where the moisture from a mist coat may reactivate the filler.

 

[jacoscar]

Would anyone answer my question?

 

[Wayners]

Use acrylic primer undercoat.
Then a quality emulsion.

If you want it to continue drying out for next 6 months use a contract emulsion which will be chalky but will do job.
Contract emulsions can be washed off. Like poster paint.

I don't ever use contract emulsion but I don't paint new damp properties.
I do paint new plaster skims after a few days drying with acrylic primer.
Then often durable emulsion.

 

[jacoscar]

If you want it to continue drying out for next 6 months use a contract emulsion which will be chalky but will do job.
Contract emulsions can be washed off. Like poster paint.

So can I just go over it with my finish coats without worrying that the mist coat can be washed off?

 

[DiyNutJob]

So can I just go over it with my finish coats without worrying that the mist coat can be washed off?

Why not experiment? It's quicker than waiting for answers.

 

[Wayners]

If I was to paint with contract matt I'd leave that on.

If I was to paint over contract matt with a durable emulsion with scrub rating maybe prime first.
Contract matt is not a great primer over plaster for durable emulsions.
Some durables say so in application data sheet.
What are you using at top coats and read the application data sheet online. Simple document..
Contract matt is very dry and durable emulsions can play up when applied over. You may need to add water to first coat to seal surface and prime. Durable emulsions have longer drying and recoat times. Follow them

 

[sparkwright]

I had my living room plastered 6 months ago, so it’s well dry

I applied this as a mist coat

Wickes Matt Emulsion Paint - White - 10L | Wickes.co.uk

Wickes Matt Emulsion Paint - White - 10L

www.wickes.co.uk

3 part paint and 1 part water
That’s 25% dilution, even though the bucket says I could go up to 40%

I just tried to brush the wall with a wet sponge and this happened (the coat was applied 4 days ago), is this normal?
View attachment 277601


It basically got back to bare plaster

I would say it would be normal for the mist coat to come off like that if you put a wet sponge on it.

Are the edges peeling. They shouldn't be, and it doesn't look they are.

You will have to touch that up with some more mist coat, as I'm sure you are fully aware of.

If I'm reading the data correctly, the emulsion is not supposed to washable anyway.

It's supposed to be good opacity, several reviewers have pointed out how thin it is and that it doesn't cover - so you may want to try something else for the last coat or two.

All you can do is try it.

***

If you are worried about it, apply some normal emulsion over the mist coat in a discreet location, to check the mist coat is sound.