Can you use a primer for a mist coat on plaster? Or are primers not good for mist coats for some reason?

[alligatorlizard]

I'm planning to paint a room using Farrow & Ball's yellow "Babouche", starting with an undercoat of their "Wall & Ceiling Primer & Undercoat White & Light Tones". The room has several plastered chases after a recent rewire, so I know I need to mist coat these areas as a first step.

What I can't work out is if I can use the primer (diluted) as a mist coat on these areas (and then once this has dried, another coat of undiluted primer all over before topcoats)

Or, do I not even need a mist coat if using a primer?? So just one undiluted coat all over?

Or, is the primer is unsuitable for a mist coat, and the mist coat should instead be done with the topcoat colour (i.e. Babouche in this case)? Followed by a coat of undiluted primer all over, then the 2 layers of top coat.

Have just been reading the Product Advice Sheet for their "Wall & Ceiling Primer & Undercoat White & Light Tones" and it seems to suggest the 3rd option - but can anyone confirm I've got this right?

If I can use their primer for a mist coat that would be great, as I've got a few spots on the bathroom ceiling I need to mist coat, and will be using Zinsser Permawhite Satin for this, which I know is definitely not suitable for mist coats - so if I can use the F&B white primer I already have as mist coat, would save me having to buy another whole tin of matt white just for a few small areas of plaster/filler in bathroom!

 

[Wayners]

What's the data sheet say for the paint?
Look it up. It will be a plain english pdf telling you everything you need to know.
Always read the data sheet

 

[alligatorlizard]

What's the data sheet say for the paint?
Look it up. It will be a plain english pdf telling you everything you need to know.
Always read the data sheet

I did already read it, but it's vague... It's basically unclear whether it's saying to use the overcoat for the mist coat (i.e. under, and in addition to the primer), or whether it's presenting two different scenarios - i.e. you could mist coat plaster with diluted topcoat, or use primer...

Hence why looking for clarification.

Presuming it's similar to other primers, in general, can you use a primer INSTEAD of a mist coat? Again, have looked this up, but answers seem contradictory... hence seeing if I can get a definitive answer here!

 

[Wayners]

Which F&B emulsion do you have?

 

[alligatorlizard]

Which F&B emulsion do you have?

Babouche, Estate Emulsion. As far as I'm aware this would be fine for a mist coat. Just not sure if their "white & light colours primer & undercoat for ceilings and walls" can be used as a mist coat on plastered areas.

 

[Wayners]

According to data sheet yes.
Under the section..

New or Unpainted Plaster/Dry-Lined Surfaces (Modern Construction) Preparation.

 

[alligatorlizard]

According to data sheet yes.
Under the section..

New or Unpainted Plaster/Dry-Lined Surfaces (Modern Construction) Preparation.

That sections says: "dilute your Farrow & Ball topcoat with 25% water and use this as a mist coat, followed by two coats of your chosen topcoat" - with no mention of the primer at all!

The previous section, "Priming and Undercoating Advice" says: "Don't over dilute the Primer & Undercoat or mist coat. This will reduce their opacity, causing an uneven finish and incomplete colour development. Before applying the top coat, consider if a second, undiluted coat of Primer & Undercoat is needed to achieve full opacity" - if the "or" I highlighted is a typo, and should be "on", then the paragraph makes a lot more sense, and implies the primer can be used as mist coat. If it's not a typo (and the subsequent use of "their" suggests it's not) then it seems to imply the mist coat is a separate paint from the primer, but isn't clear if it has to be...

I'm probably asking a question that's obvious to anyone who's painted before, but as someone who's not, I just need to know if a primer can be used for mist coats, or if some quality of primers (e.g. the fact it seals in what's under it) prevents it from being a good mist coat?

 

[Wayners]

Don't over dilute the primer or mistcoat.
I read that as..... don't add more than 25% water to either the emulsion or the primer.
It's very common for people to do that causing problems..
It's a bit generic as data sheet is for both emulsion or primer.
It mentions both are similar products so I guess the data sheet is covering both.
It's not very clearly written as you pointed out.

 

[alligatorlizard]

I did wonder if that might be problem, i.e. generic data sheet for multiple paint types. So many data-sheets/instructions have ambiguities like this - really, would it kill them to clearly state the obvious questions?!?

Anyway, from what I can tell from other FAQ's around the web, primer's probably fine for mist coat so long as it's water based (which this one is). There's a lot to figure out when painting a house...!

 

[Wayners]

The primer is mentioned.
As I understand it most paint manufacturers recommend diluting the emulsion as a base coat over plaster.
If you have contract emulsion on surface or something a bit grubby then use the primer. It gives a clean sealed surface.
It's because the resins in the emulsion can react or not get chance to level out if the surface is dry . Also helps with opacity.
It's a problem with durable (scrub rating) emulsions. You need a sealed surface for the emulsion to be applied to.
I always sprayed plaster with first coat vs rolling as it's a flawless application. New properties are sprayed now as well.

Any questions you have phone the technical helpline.