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About the Author: livescience


  1. Probably a better sub for this. But seeing this brings a question to my mind.

    Paint thinner can be used to thin paint. Besides its applications in preparing a paint sprayer, is there a reason to thin paint? Does it make for a smoother coat or something?

  2. Yeah, fun fact, you can get a really awesome paint finish by aggressively mixing paint thinner or even paint stripper into the paint just before applying it. A friend of mine refinished a guitar of mine and got it a kind of hammerer copper look that way.

  3. Paint is primarily made of 4 main components. A pigment, like titanium oxide which imparts white color to paint. Pigments are usually nano-micro scale particles dispersed in the mixture. A resin, that binds the pigment to a continuous liquid. This is usually a polymer of some kind, like polyester. So the liquid is a huge number of convoluted chains that are all entangled with each other. A solvent, such as acetone which dissolved the polymer and keeps it a thin liquid. The greater the amount of solvent the easier the fluid flows. And the final component is usually an additive that includes smaller chemical compounds or polymer chains that serve to change the rheology of the liquid. An example would be chemicals added to increase mould resistance.

    There are many complex paint mixtures and they often have different drying mechanisms based on their make up. The simplest one to understand is when the solvent, a highly volatile compound like acetone, evaporates leaving behind a polymer mixture with many small pigment particles uniformly mixed in. The polymer thickens and stiffens as the solvent evaporates, drying to form a coat.

    I’m not sure what’s happening here but I would guess that as the solvent evaporates a concentration gradient of polymer builds up near the surface. To minimize the surface energy of the fluid gas interface, we see the patterns forming. The polymer begins to diffuse back down into the bulk as there is a concentration build up near the surface and the solvent begins to diffuse to the surface because there is a concentration in the bulk. But as the solvent is made up of small molecules compared to the long polymer chains the solvent diffuses much faster through the polymer leading to a thicker fluid near the surface and a thinner fluid in the bulk. This loss of solvent will continue to occur until a new equilibrium concentration is obtained.

  4. See something like this at work all the time. Spraying silver anti seize off of vehicle hubs with break cleaner does this as well.

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