Why can “permanent” markers be erased by dry erase markers on certain surfaces?
In: Chemistry
Permanent markers use a single quick evaporating solvent. Once it evaporates the dissolved solids are firmly attached to the surface.
Dry erase markers use two solvents, one quick evaporating, and a second that evaporates very slowly (over months). When the quick solvent evaporates the slow solvent remains, so the dissolved solids are left as a thick sludge, which can be smeared and erased.
When you rub dry erase over permanent marks the quick solvent re-dissolves the solids, leaving them suspended in the slow solvent as if they’d been dry erase in the first place.
If you leave the dry erase marks long enough the slow evaporating solvent will evaporate, leaving marks nearly as solid as permanent marker.
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