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What Actually Happens When The Paint Dries?


Piotr Parda, "All You Need Is Time", 2017, altered old painting


Let’s say you just painted a fence and now you are watching the paint dry just because you have too much time on your paint stained hands.

Boring?

Not if we take a closer look.

Paint usually consists of two elements: the pulverized pigment - usually a mineral or various oxides and a medium (or binder).

Application is possible because the medium binds the particles of pulverized pigment into a uniform and sticky… goo and becomes quite durable after drying.


If the medium contains water, the drying will depend on the evaporation leaving just the binding substance which keeps the particles of pigment together. In watercolors this substance is gum Arabic, honey and/or resin. Egg yolk in temperas.


Water itself wouldn’t help the paint stay on the surface. After its evaporation the pigment would get back to being its former pulverized self (which explains the low durability of chalks).


Evaporation and binding causes some of the volume of the paint to shrink and stretch on the surface, especially because a lot of pigment fill up all the tiny holes and gaps in the painted surface, no matter how well primed and smooth it was. Most colors will also darken upon drying. It is important to select the color based on its dried shade.

This stretching is the reason why one coat of paint is not enough to ensure a uniform surface. With increased transparency of the paint, more than two coats should be applied. The most transparent pigment is usually red and crimson. There just hasn’t been one opaque enough. Too much transparency is not the only reason why painting things red might drive you crazy. The color red influences our mind psychologically triggering a feeling of alert and even irritation.


I recommend green.

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