Ink and paint

[Jona Lendering]

I just put online the text of the Deir 'Alla inscription (nothing military, but still an interesting ancient text that happens to mention the Biblical prophet Balaam). It is some kind of fresco, but the excavators tell that it was written with ink. This makes me wonder what's the difference between ink and paint.

Under normal circumstances, I would say: both are writing materials and are made of more or less the same material, but one is more fluid than the other, because it is used to write on paper or parchment, while the other is a bit sticky because it has to be used on a vertical surface. Apparently, that's not true; but what is the difference?

[Epictetus]

Instead of ingredients or attributes perhaps the difference could be in their intended use? Ink would be more likely to be used in texts, while paint would be more likely to be used in illustrations.

[Theodosius the Great]

Is one more durable than the other ?

Paint is more likely to used outdoors while ink is used on fragile
paper which is stored away from the elements.

When the letters from Vindolanda were discovered the ink was still
visible to the naked eye for a few minutes but disappeared shortly
after being exposed to the air. The only way to read the letters was
via infra-red scans.

~Theo

[Bill Thayer]

Jona, I think you're on the mark: the way I understand it, the formulation of paint includes a binder, ink does not. The article Atramentum in Smith's Dictionary tantalizingly mentions an atramentum pictorium ("painter's ink"), just once though — and the dictionary has no article on paint; the latter was too far from those classicists' books....