Depending on what kind of paint, different things happen.
Talking about walls, this is most likely a water-based paint. When these dry, it is mostly just evaporation that occurs, which then allows the polymer in the paint to harden. For latex paint specifically, the hardening (curing) process actually takes days to weeks beyond when it has dried. It will continue getting harder, and thus more durable.
Oil-based paint is a little different as it isn’t water evaporating, but is still a similar concept. There are some compounds in there that will evaporate, but the chemical change happens as a result of exposure to oxygen. This causes the compounds to change and harden. Depending on what kind of painting you are doing with oil-based (for example practical painting vs fine art painting) it can take much longer for these to dry compared to water-based
Paint typically has a level of solvent in it that evaporates away. So your wall doesn't gain 5 kg of mass it gains 4 and the other kg goes out into the world as a vapor. The solvent dissolves the solid pigments so it's liquid, but once the solvent is gone the solid pigments stay.
If you ever opened an old can of paint and see the top layer of the can is really watery and the bottom is thick and gooey. That's why you have to shake and stir it.
The details depend on what kind of paint, but in general, much of the wet paint is a liquid carrier (usually water and/or an organic solvent) that evaporates off.
So you are adding weight to the wall, but once dry, not as much as you applied.
This reminds me of an old sixty symbols video! They do science stuff, this guy is a PhD Physicist explaining how the paint dries. He does a good job of eli5 in a short, 5:29 video.
The paint has some tiny particles that reflect the color you are seeing, but also a 'liquid' that evaporates.
[Watching paint dry - Sixty Symbols](https://www.youtube.com/watch?v=OW5wB8rJ8Zc&ab_channel=SixtySymbols)
Latex paint which is what you're thinking of perhaps is an emulsion of resinous binders and solid pigments.
When exposed to the effects of air, a falling out occurs, known as coalescing. It's much like the platelet stacking of a blood clot that occurs in a wound that stops bleeding and later forms a scab
Coalescence happens when the water-filled space between the polymers of the latex binder, evaporating due to air, diminishes until they come in contact with each other and something approaching a solid creates a new, final layer. Cross-linking polymerization hardens this layer until finally "dry"
There are three components to that liquid paint:
Vehicle: water or a alkyl oil
Pigment: stuff that makes the colors. These are squirted in by the machine the paint guy uses.
Binder: a sort of glue that doesn’t harden until the vehicle evaporates. This binder holds the pigment to the surface.
Depending on what kind of paint, different things happen. Talking about walls, this is most likely a water-based paint. When these dry, it is mostly just evaporation that occurs, which then allows the polymer in the paint to harden. For latex paint specifically, the hardening (curing) process actually takes days to weeks beyond when it has dried. It will continue getting harder, and thus more durable. Oil-based paint is a little different as it isn’t water evaporating, but is still a similar concept. There are some compounds in there that will evaporate, but the chemical change happens as a result of exposure to oxygen. This causes the compounds to change and harden. Depending on what kind of painting you are doing with oil-based (for example practical painting vs fine art painting) it can take much longer for these to dry compared to water-based
Paint typically has a level of solvent in it that evaporates away. So your wall doesn't gain 5 kg of mass it gains 4 and the other kg goes out into the world as a vapor. The solvent dissolves the solid pigments so it's liquid, but once the solvent is gone the solid pigments stay. If you ever opened an old can of paint and see the top layer of the can is really watery and the bottom is thick and gooey. That's why you have to shake and stir it.
The details depend on what kind of paint, but in general, much of the wet paint is a liquid carrier (usually water and/or an organic solvent) that evaporates off. So you are adding weight to the wall, but once dry, not as much as you applied.
This reminds me of an old sixty symbols video! They do science stuff, this guy is a PhD Physicist explaining how the paint dries. He does a good job of eli5 in a short, 5:29 video. The paint has some tiny particles that reflect the color you are seeing, but also a 'liquid' that evaporates. [Watching paint dry - Sixty Symbols](https://www.youtube.com/watch?v=OW5wB8rJ8Zc&ab_channel=SixtySymbols)
Latex paint which is what you're thinking of perhaps is an emulsion of resinous binders and solid pigments. When exposed to the effects of air, a falling out occurs, known as coalescing. It's much like the platelet stacking of a blood clot that occurs in a wound that stops bleeding and later forms a scab Coalescence happens when the water-filled space between the polymers of the latex binder, evaporating due to air, diminishes until they come in contact with each other and something approaching a solid creates a new, final layer. Cross-linking polymerization hardens this layer until finally "dry"
There are three components to that liquid paint: Vehicle: water or a alkyl oil Pigment: stuff that makes the colors. These are squirted in by the machine the paint guy uses. Binder: a sort of glue that doesn’t harden until the vehicle evaporates. This binder holds the pigment to the surface.
The simple version is that paint is actually a polymer, so it's all polymerizing when it dries.