Yellowing
Do floor coatings turn yellow?
Sunlight ambers some resin chemistries, so a floor shifts color where the light lands, and the top coat is the layer where that difference sits.
The short version
- Ultraviolet light breaks down some resins, and the visible result is an amber shift.
- It shows first where the sun reaches: a strip inside the door, and wherever a window puts light on the floor.
- The top coat is the layer meeting the light, so its chemistry is the one that matters here.
- A light solid color shows a shift sooner than a dark flake blend does.
- A basement with no daylight in it is asking nothing of a top coat this way.
What sunlight does to a resin
Ultraviolet light carries enough energy to break chemical bonds, and some resin families have bonds it can get at. As those come apart the material stops throwing light back the way it did, and what a person sees is a warm shift: cream going tan, gray going slightly gold, a bright white going the color of old paper.
It is a surface effect and it arrives slowly, so it is easy to miss on your own floor and obvious the day somebody moves a cabinet that has stood in the same spot for a long time. The concrete under the coating is not doing anything. All of this is happening in the top fraction of the film.
Where it shows first
Follow the light. In most garages that is a band inside the overhead door where the sun comes in low in the afternoon, and it stops in a line right where the door shadow falls. A service door with glass in it prints its own rectangle. Under a workbench, back in the corners, and everywhere a car normally sits, nothing changes.
Outside is a different question again, because a patio, a pool deck or an entryway sits in full sun all day with nothing over it. A floor in that spot is asking much more of a top coat than a garage does, and that is the first thing to say out loud while the coating is still being picked.
The layer that meets the light
The top coat is the only part the sun ever touches, so the chemistry of that one layer is what this comes down to. Some resin families are built for outdoor exposure and hold their color far better under it. Others are used underneath, where they do their work in the dark and are never asked to face a window.
So the question worth asking about a quote is what the top coat is and whether the floor it goes on gets direct sun. Color helps too: a mid tone with flake in it hides a small shift that a flat light gray would show. Say where the light comes in while somebody is standing on the floor with you.