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I am spray painting my cabinet doors.

The first and second coats are good. However, I see cracking on the edges of each door after third coat. The surface is good, quite smooth.

enter image description here

Do you know what could be the problem?

My paint expired a little bit. The humidity is 74%. But I didn't see same problem when the first and second coats were applied.

I am using GRACO HANDHELD sprayer with 414 tip. Paint is water based.

  • 2
    Looks like the coat is too heavy for those details. What was done for paint prep and primer? – Harper - Reinstate Monica Sep 25 at 5:13
  • It's new maple door. I didn't use primer... Will it be the problem? – XWLI Sep 25 at 5:40
  • The paint I used says it's self-priming: [BRAND-NAME] Semi-Gloss paint is a self-priming, medium to high sheen, protective finish that dries to a hard, durable film. Ideal for interior walls & ceilings, trim, furniture, and other woodwork, such as cabinets. – XWLI Sep 25 at 5:46
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    "Self-priming" is really just a marketing term that means little more than "good coverage", and simply contrast it with paints which were common a couple decades ago that covered poorly. It doesn't negate the need for primer for certain cases, particularly over glossy and porous surfaces or stains. It's also always a good idea to prime over darker colors and any red paint despite the "self-priming" lingo. – Nate Sep 25 at 7:27
  • Maple is a closed grain wood though, so it isn't nearly as porous as pine or oak. It generally takes paint well without priming. If that edge has end grain, though, that would be the most porous part and may explain the cracking. – Nate Sep 25 at 7:44
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You laid it on too thick, because nooks are tricky to paint for several reasons.

This was greatly exacerbated by not using primer.

Whenever the paint industry claims something, they mean it in a certain context. For instance I see a lot of brushes and rollers "for all paints". Yeah, they melt and come to pieces when I roll a marine LPU, because what they really meant was "All paints sold in Home Depot (except the garage floor epoxy)".

When they say "self-priming" what they really mean is "On drywall or pre-painted off-white surfaces" and it's a brag about their coverage.

An important job of primer on raw wood is to block moisture and oils. It might have been moisture pushing out the end grain, but probably not. Mineral-based primers made for wood do a good job of this.

You didn't mention this, but I bet the whole reason you came back for a third coat is the coverage was poor. The maple was printing through the paint, either from color, absorption or texture. This falls into two areas that are primer's job too:

  • Make the entire surface consistent (behaving the same): For instance, end grain absorbs diluent and paint differently than side grains. This effect will "print through" paint, making the end grain look different. Primer's job is to stabilize this no matter what, and provide a stable base that can be sanded to remove flaws. One last primer coat is added to make the sanded work consistent. So the topcoat is covering one uniform surface that has the same texture and absorption.
  • Make the entire surface the same color, reasonably near the topcoat ultimate color. Without this, any color differences in the substrate will "print through" - will be noticeable in the topcoat, because topcoats are not opaque. In particular, it is a massive fad to have all house paint be off-white. As such, architectural coatings are expecting to overpaint surfaces which are already off-white, and they don't have the strength of pigment to deal with deep colors. Primer's job is to be effectively more tint coats to cover and equalize ineqaulities, like wood grain.

The next coat of a paint can partially reactivate the last coat; that's how it bonds (without having to scuff-sand for a purely mechanical bond). I'm not sure whether your third coat reactivated the first two, or you were just hitting the third coat extra hard to avoid a fourth, but the stack ended up too thick to dry without cracking.

By splitting the "coverage" task across two totally different chemicals, you reduce that layer thickness - you are applying two thin paint systems instead of one thick one. It also helps if the primer is a different chemistry, e.g. 2-part epoxy or alkyd, and that even helps the primer do a better job.

But I would say, next time, prime with an aklyd wood primer, until the surface is monochrome and as you like. Then you will use less paint and you won't have defects arising from thickness.

  • Thanks a lot for explaining so detail! I think I understand the problem now. Can't wait to see if I can do it better for next batch of doors. – XWLI Sep 25 at 22:04
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Might be caused by the second layer shrinking beneath the third layer because it hadn't fully dried. In high humidity conditions, I generally increase the recommended drying time between recoats by 25%, just to be safe.

Alternatively, if the backside of the door has been stripped and hasn't been resealed, the door itself may be expanding slightly due to the humidity.

I haven't actually had this happen before on something like a cabinet door, so these are just guesses based on experience with painting outdoors.

  • Thanks! actually the third coat was applied two days after the second one. So I assume it's drying time is good enough... – XWLI Sep 25 at 5:52
  • That should have been plenty. If the other side is properly sealed, I'm not sure what the problem is. – Nate Sep 25 at 7:24
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    I have seen moisture in wood cause a problem as part of Nate answer points to. – Ed Beal Sep 25 at 14:05

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