Mist coat with oil-base

[bsr]

Hi Guys

I'm painting over filler using oil-based eggshell. Should I mist coat, and if so what should I dilute with - white spirit?

Thanks in advance

 

[dcdec]

Do you mean that you're spot priming where you have filled prior to a top coat?

If so and the wall is suitable for oil based eggshell (have to think why tho in this day and age) you can thin with white spirit and suggest you apply with a mini roller to avoid unsightly brush marks, hard to say as i do it by feel but about 20-25 % at a guess.

If you're painting fresh plaster you need to use an alkali resisting primer before any oil based finishes to avoid saponification

 

[bsr]

Thanks for your reply. A bit more detail:

• The wall was originally painted with several coats of emulsion
• On top of that are two coats of oil-based eggshell, used because it was recommended on this forum as a good paint for a bathroom
• The paint is cracking and peeling; when it comes away it leaves bare plaster
• My plan was to rake out and fine fill the gaps, then overcoat with the same oil-based eggshell
• How should I prep the filled surface? I know I can't put oil-based directly onto plaster because of saponification, so should I prime with primer, or can I mist coat with diluted eggshell (because I'm painting onto filler, not plaster)?

Thanks!

 

[dcdec]

If i was you, i'd try and get away from the oil based eggshell. I think you were badly advised to apply it when water based does the job very well.

So the first thing to do is apply a sealer coat. For this i'd use zinsser coverstain, gardz or bin (bin is tricky to use and stinks). Then do your filling and prime it with a diluted water based paint such as eggshell or emulsion.
You can now apply an acryllic eggshell to your walls. When doing this cut in, allow to dry then roll, this will avoid flashing.

It may be a little long winded but you'll be free of smelly alkyd paint and the water based will not be brittle and is unlikely to crack (unless there is some kind of underlying problem).