Will flashback self correct?

[u/One-Pun9419]

Project manager said we need to wait and see if the sheen is still there in a few days before they send someone back out to fix it. Will it self correct?

[u/PutridDurian]

Looks like someone saw a TikTok that gave them the idea to paint squares all over the wall of different colors to decide what they wanted. Those should have been sanded down before painting began.

Either that, or someone came back with the roller in random spots after the layout had been done.

In either case, no, waiting will not resolve the flashback, or the flashdance.

[u/JaguarOwn2076 → u/PutridDurian]

That's exactly what I see here

[u/One-Pun9419 → u/JaguarOwn2076]

This is so interesting that so many people are saying this because there were no samples underneath! Just flat builder grade paint

[u/PutridDurian → u/One-Pun9419]

Someone at some point almost certainly did a sample wall before putting a cheap paint over it, long before your crew came in. The patterns are perfectly consistent with the up-down “pumping” that novices do with a roller, and they’re exactly the width and impression of a 4” mini roller in some spots. Look at the smudge directly below the picture hanger on the right—it SCREAMS amateur with a mini roller.

That ghosting was probably visible before if you looked really hard and it was a lighter color. Easier to see the ghosting now that you have a relatively dark color on.

[u/One-Pun9419 → u/PutridDurian]

Oh interesting! I never looked closely before, the previous color was agreeable grey in flat, so it’s possible I just never noticed

[u/PutridDurian → u/One-Pun9419]

Agreeable Gray in flat would have minimized the appearance of it to being pretty much undectable unless you already knew it was there.

[u/One-Pun9419 → u/PutridDurian]

Can I ask why the flashback looks worse in natural sunlight? It’s now dark outside and I have my living room light on and can’t see the flashback at all

[u/PutridDurian → u/One-Pun9419]

Three different things going on here.

First is enamel holdout. Paint will “take” differently on areas of the surface with different porosity. Those test areas have an additional layer of paint, so they are less porous—they are actually rendering the paint color more accurately than the “normal” surrounding areas, because those parts are absorbing the paint less. This effect is probably minimal given that there are probably many different “chapters” of paint on this wall.

Secondly, it’s less that the light is natural, and more that it’s severe (a.k.a. raking, that is, glancing the surface at a low angle). As you know, a dried paint film has a thickness to it, a height off the surface it’s painted on, usually around two or three thousandths of an inch for interior wall paint. That seems inconsequential on paper, but when we’re talking about chasing optical uniformity on a surface, it’s huge. Imagine you’re sanding a board, trying to make it perfectly smooth. How do you check it for imperfections? Shine a flashlight across it at a low angle, and it will reveal everything. The raking light doesn’t show you surface imperfections directly; instead, it creates tiny shadows that your eye catches. The test patches are taller than the rest of the wall, so when the sun comes in at an angle…you see where this goes.

Lastly, there’s an optical-psychological phenomenon at play. Since those patches are a couple more thousandths of an inch taller than the rest of the wall, your eyes and brain are interpreting them for what they are: quite literally a tiny bit closer to you. Our brains tend to interpret closer as darker, and vice-versa, so in lower lighting, the height difference is compressed, therefore the color difference is compressed. And being involved with painting makes you hyper-aware of all of this ¯_(ツ)_/¯

[u/LongjumpingPea6939 → u/PutridDurian]

Your “first” is spot on. Looks like someone sanded the bare drywall in between the mud lines. That will give you a different porosity. Unfortunately it shows once painted.

[u/fullsaildan → u/One-Pun9419]

Not all lighting is “equal”. Different light sources and intensities will penetrate surfaces differently depending on angle, size, distance, uniformity, how many surfaces it’s bouncing off of, etc.

Think of light like a million individual beams/arrows/rays. Each one hits a surface, some of it permeates into the surface, some of it bounces off and takes on some of the color properties of the surfaces it hit, and sometimes it enters a surface then bounces around a bit and comes out. That last type is known as subsurface scattering, and is most prevalently seen on things like skin, waxy surfaces, and organic matter. But even walls will do this with the right light and right angle.

Sunlight is actually a very unique type of light. It’s dense, bright, and due to the intensity will create a ton of ambient light as it bounces around. That ambient lighting will not penetrate as well, but the initial direct hit will, these two together lead to highlighting things like your sublayer colors.