Outer Space

Can paint dry in outer space? Or would it stay wet forever. ?
(I’ve been watching Red Dwarf)

WAG: There’s no water in paint. It’s really just a process of the molecules forming polymers and solidifying. There’s no evaporation going on.

Depends on the type of paint. Lacquers only dry by evaporation of a solvent; there are no other reactions going on. Enamels may or may not have a volatile solvent, but they primarily set b y some sort of polymerization process, as you note.

If there is evaporation (I don’t know much about paint), it would happen even faster in a vacuum, for the same reason water boils at a lower temperature at higher altitudes. The evaporation rate is dependent on the vapor pressure of the substance in question (it can be solid and subliming also) and the ambient pressure. If the ambient pressure is higher, there will be very little, if any, evaporation, because the system will be at equilibrium. If the ambient pressure is zero, the volatile molecules (i.e. the ones moving the fastest) will fly off with impunity (allowing of course for Van der Waals, etc.)

I thought most paint is water-based these days?

Yes. I.S. was right and wrong. Yes, there is water in paint. No, the paint is not “drying,” it’s polymerizing.

This is like saying that a glass of salt water is crystalizing but not drying as the water evaporates. Yes, it is true that the sodium chloride is crystalizing, but it is doing so because there is no longer enough water to keep it in solution.

Similarly with paint, as the solvent evaporates from a liquid paint or surface coating, the ability of the molecules that make up the binder are no longer free to move and tend to either adhere to the substrate, or undergo the structural chemical changes of cross-linking and polymerization. Although the latter processes are generally categorized as curing rather than drying, they are initially inhibited by the presence of the solvent which evaporates away; in the case of latex or natural pigment paints, water functions as the solvent, whereas in oil-based paints it is the oil (which is generally considered an emulgent or emulsifier rather than a solvent). So saying that paint is drying is (at least for common liquid paint that most people are familiar with) this is an entirely accurate if not comprehensive non-technical description.

There are dual-base paints, e-coats, and UVC coatings, and other types of coatings that do not use a solvent or emulgent, instead requiring some kind of catalyst or external energy source to cause the paint to adhere, polymerize, and cross-link without an evaporating solvent or emulgent. These are especially used in applications requiring highly durable coatings which were previously applied using volatile organic compounds (VOC) as the solvent agent. However, what the average person thinks of as “paint”, i.e a gallon bucket from the Sherwin-Williams store or RustOleum contains a solvent which triggers curing as it evaporates.


In Space, No One Can Hear You Scream About How Boring It Is Watching Paint Dry.

Perhaps in the titles for Red Dwarf Lister was using some kind of special sci-fi space paint. He was also somehow managing to stand on a gantry without floating off into space.

The liquids in paint would evaporate of sublime, so if you can spread it it will dry. Just remember to decompress the can before you open it in the vacuum of space.
Bada Boom Bada Bang!