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I've built a small office desk and a shoe rack out of pine and now plan to paint both. The most used parts, i.e. table top of the desk and the shelves of the shoe rack are going to be black, the rest will be in white. The desk will be used for work (laptop and stuff) and eating.

I was planning to apply oil based polyurethane spray (matte finish) over glossy latex paint (already bought all the materials), but then realized that the oil based polyurethane does yellow over time. I kept googling and found out that even water based polycrylic yellows on white paint, and I was planning to cover the furniture pieces in whole. So now I'm pretty confused on what to do.

So, my questions are:

  1. Is it fine if I only apply top coat to the most used (black paint) parts?
  2. Will oil based polyurethane visibly yellow over black latex paint? How soon will it happen?
  3. What alternatives do I have?
  4. If I don't apply any top coat, how long would my table top & shoe rack shelves paint "live" for on average?

P.S. Water based polyurethane and polycrylic are pretty expensive (and polycrylic is extremely rare) at where I live, and I don't feel like spending that amount of money.

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  • Hi, welcome to Woodworking. Poly is not strictly needed to overcoat painted furniture, and if you pick the right black paint it won't make a huge difference to the overall durability. That said, what you've probably bought may not be the most durable of paints, but it's impossible to be definitive because "latex paint" has become a catch-all term for waterbased paints in some markets, and even within specific classes there's little consistency across the board.
    – Graphus
    May 5 at 6:09
  • @Graphus Hi and thanks for the answer! The table top is what I'm most concerned about, whenever I google it it usually says "you need a top coat on heavy traffic areas such as table tops, etc". Here's some of my paint's description if it helps: "100% Acrylic Quick Drying Enamel (Water-Based)... a high gloss 100% acrylic water-based paint formulated to replace conventional solvent-based alkyd enamel... dries to a tough and durable finish due to its room temperature, cross-linking capability."
    – Alexander
    May 5 at 6:36
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    Right, this is a superb example of what I referred to — that paint description is very reassuring and I would never refer to something like this as latex paint (latex often reserved for referring to waterbased wall paints, but even these vary). Anyway, there's no telling how tough your paint actually is, but it is exactly what I would look for myself if I wanted a substitute for oil-based enamel :-) Based on the blurb there's a decent chance it doesn't need overcoating for a desktop. "you need a top coat on heavy traffic areas such as table tops" Does this specifically refer to over paint?
    – Graphus
    May 5 at 8:14
  • @Graphus it was my mistake calling it "latex", I just supposed latex = acrylic = water based paint. "Does this specifically refer to over paint?" - hmm, I think so. And it does say you can use Poly on top of "latex" paint everywhere on the internet.
    – Alexander
    May 5 at 9:26
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Is it fine if I only apply top coat to the most used (black paint) parts?

To answer this generically, sometimes yes, sometimes no. Adding a clear finish such as lacquer or varnish over paint can offer increased protection, and with some paints this may be needed for the expected use. So a lot depends on the paint chosen.... some paints are more than capable of holding up over extended periods and some high-wear usages without any help.

In your case, based on the further description of the paint you bought from the Comments, there's a decent chance it doesn't need overcoating.

Will oil based polyurethane visibly yellow over black latex paint? How soon will it happen?

Oil-based polyurethane is already slightly yellowish (or more accurately, amber). It just becomes slightly darker and more orange/tan over time with ageing and exposure to light. This darkening takes a few years usually before it's noticeable.

But, you don't really have to worry about this since you basically can't see a yellowish clear finish over a black background.

Two further things to bear in mind however:

  • The curing period for oil-based poly is long, up to a month. So if you do use it your desk won't be available for normal use, where you don't have to baby it, for at least two weeks and possibly double that, depending on local conditions1.

  • Matt varnishes don't hold up as well as more glossy variants, in terms of maintaining their original look. The main issue is that the matt surface can become buffed by use, leading to glossier areas especially along edges, but even where you commonly rest the heel of your hand using a mouse or over the edge of a laptop can create a shiny spot.

Water based polyurethane and polycrylic

Same thing.


A few application pointers:

  • In case the application guidelines for the paint don't make this plain, it is far preferable to paint multiple thin coats than fewer thicker coats. I would aim to apply four thin coats to the top of the desk, and fewer elsewhere2.

  • In addition to the above the first coat can the thinned quite a bit so that it sinks into the wood more deeply. (IME you can do this safely even if the paint's instructions say not to thin the product.)

  • I'm personally a big fan of using foam rollers for applying waterbased paints, but you may not like the subtly textured surface this often produces so would prefer to apply the paint conventionally.


1 The rule of thumb is that varnish can be considered cured once you can no longer smell it with your nose right by the surface.

2 On non-critical surfaces once full coverage was achieved I'd generally stop, unless I was feeling particularly conscientious that day :-)

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    Thanks for breaking things down in detail! The paint can refers to itself as "Top coat" and they recommend 1 coat of primer (of the same brand) and 2 coats of top coat (the paint itself). So I guess I'll do it without Poly and see what happens, I'm curious of the results anyway since it's my first time. And I'll be able to re-do the job with Poly if paint does come off too soon. I bought a matte Poly because I wanted matte finish, but also read that matte paint is less durable while matte Poly can give you a matte finish even over glossy paint. I might've googled too much unrelated info :)
    – Alexander
    May 5 at 9:42
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    "I might've googled too much unrelated info :)" :-) While you can never know too much it is easy to get information overload early on, when you're not sure what you need to know. Yes matt poly can give you a matt finish over glossy paint (or glossy varnish.... which is actually the right way to do a matt varnish finish, not multiple coats of matt). And also yes, matt paint (matt finishes in general) are less durable overall. It's not necessarily that they'll wear off faster, but the change in look from buffing is hard to avoid.
    – Graphus
    May 5 at 11:41
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    "I'm going to use primer first, so I think the "first coat sinking" thing won't be an issue?" Correct, skip the dilute coat if priming. While only a few years ago I would have said otherwise I don't actually think primer is essential (on wood), but if you want to do this textbook then priming is the right call. Re. number of coats, be guided by the product directions as much as anything.... it'll probably suggest 2 or 3. I'd be unlikely to do 4 in this case, and only 2 could be enough as black paint tends to have good coverage. Your white paint might too since white pigment is very cheap.
    – Graphus
    May 5 at 11:47
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    Oh P.S! Something I meant to mention earlier — are there any knots in the item to be painted white? Knots in pine and other resinous woods need to be sealed prior to painting, if not sealed successfully over time where the knots are you'll get a yellow/tan stain. It's possible the primer you get might not be enough for this (check what it says). They do make stain-blocking primers but these tend to be expensive. But plain shellac, of any colour, will do the job perfectly, and shellac tends to be much cheaper as well as having multiple future uses for the woodworker.
    – Graphus
    May 5 at 11:53
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    You're welcome, glad to try to help. Re. the knotting products, those are just marketing names used in Britain and Ireland, I'm not even sure if similar products are sold in other markets. But what's in the container is merely a strongish solution of dark shellac. If you were to buy shellac because you wanted it for future uses as well I would advise getting it in dry form (usually flakes, but sometimes in these large, thick buttons) and making up small quantities that you'd use up before it goes off. Dry shellac stores almost indefinitely, but once made into solution it lasts ~6-12 months.
    – Graphus
    May 6 at 7:15

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