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Most widely available wood undercoat seems to be either white or dark grey. What would be best for a mid-tone top coat?

Context: I've found I need 2-3 coats of an expensive (brand name) eggshell over a white undercoat. I'm not keen to spend the extra ££ on their own brand recommended undercoat and it's not stocked at my local shop anyway.

I know this is a bit subjective and hard to answer without images, but I'd appreciate some guidance before buying a tin of dark grey to try out.

  • This question is probably best suited for the woodworking stack exchange. woodworking.stackexchange.com – Alaska Man Mar 4 at 18:00
  • Surely a question about paint is more relevant as a general DIY question than specifically woodwork. I'm painting wood, but the question would apply to any surface being undercoated. – Tim Mar 5 at 9:34
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Like you say, everything is relative. Architectural coatings are extremely biased toward white. I knew that's what you were talking about the moment you said "eggshell" :)

So I suspect all the colors you are contemplating are in fact pastels or off-whites. Truly dark (Munsell 0-7 lightness) or deep (3+ chroma) colors in interiors are simply not in style, and haven't been for 50 years. Here, see how the only color fit for architectural use is the top left (8 lightness 2 chroma)?

enter image description here
Munsell. Lightness is 2-8 bottom-top, chroma is even: 2 4 6 8 10.

When you have a "dark" (by architectural standards; probably 5 lightness) primer like this, it's for one of two reasons: First, because the chemistry of the stuff makes it better at its job; that's the case with Rustoleum Rusty Metal Primer for instance, or the mil-spec aluminum primers (the green on airplanes). Or: Second, it's tinted for undercoating extremely deep or dark colors like for warning signs or actual black or anything on the bottom half of that chart.

If the primer is merely done for color reasons, then, consult the factory, but they may allow you to add a little dark primer to white primer to dial it in to the lightness of your topcoat. But be careful; a little dark goes a LONG way! The reason to do this is to reduce the number of coats of topcoat needed for reliable coverage.

It's a regular thing for me to use Rustoleum Rusty on bare metal, followed by Rustoleum White primer, followed by 2 coats of an off-white. The Rusty is there for rust protection, the white primer is there to reduce the number of topcoats needed.

As always, primer is cheaper than topcoat, and good and proper prep is cheaper than recovering from lazy prep.

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  • gray primer is also good for coating surfaces with high-contrast markings on them, when you want to have a unifiorm pale finish. follow it with a white undercoat. – Jasen Mar 5 at 4:55
  • Thanks for the thorough answer. Can you link to a larger version of that chart please? – Tim Mar 5 at 9:35
  • It never occurred to me to mix the dark grey with some white of the same! I will try that. – Tim Mar 5 at 9:36
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    @Tim it was a found image on the web that was that size. Here's someone else's scan of that same page, but something was lost in translation... toridallasartwork.blogspot.com/2014/09/hue-5g.html – Harper - Reinstate Monica Mar 5 at 23:09

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