As asked in the question and also, a bonus question: which property of a chemical would make it 'permanent' in terms of markers?
The "permanence" is just a reference to it being waterproof.
In general, the ink comprises a main carrier solvent, a glyceride, a pyrrolidone, a resin and a colorant.
This is mostly the result of solubility. There are other markers sold on the market with labels such as "buff proof" (slang for removal proof), that are really just pens that use a different carrier solvent. With those, typically organic solvents would be the correct solvent for removal.
Basically, ink is a liquid or paste made up of pigments or dyes that is used to color a surface to create printed words or pictures. Modern inks are often made of complex combinations of various chemicals, including solvents, pigments, dyes, resins and other materials.
The chemicals found in permanent markers--xylene, toluene and urethane resin--are what give these markers their characteristic abilities to handle unusual surfaces and leave long-lasting messages. While substantial or prolonged exposure to these chemicals is harmful and toxic, the amount present in a permanent marker is minimal for the casual user.
This is what I got from google search. The above mentioned chemicals are most oftenly used, which make ink permanent. However If you have notice you would realise that the ink actually is not permanent, it fade away after certain period of time!
In my experience, ink of a permanent marker can be removed by drawing over it with a non-permanent marker and wiping it off (success depends on surface). The same goes for non-permanent writing that can't be removed because it is too old. Expo (apparently a company that sells markers and related stuff) confirms this in their FAQ
the big question:
how do I get permanent marker off a whiteboard?
No worries if those pesky permanent markers make their way into your whitespace. Just draw over it with an Expo Dry Erase Marker and poof! It's gone.
From this I would conclude that non-permanent markers contain some solvent that permanent markers lack. But obviously, permanent markers need some solvent, too. Otherwise, you wouldn't be able to write in the first place. So it must be some solvent that evaporates quickly while the solvent in whiteboard markers doesn't.
the main ingredient is isopropyl alcohol, which is sometimes called "rubbing alcohol." Other ingredients may include 2-butoxy ethanol and (di)chloroacetic acid.
ISOPROPANOL (ISOPROPYL ALCOHOL), 2-PROPANOL, DIMETHYL CARBINOL
2-BUTOXYETHANOL (ETHYLENEGLYCOL MONOBUTYL ETHER), BUTYL CELLOSOLVE, BUTYL GLYCOL, GLYCOL ETHER EB
Given the wide range of possibilities, the actual chemicals used probably depend on the marker's brand. Isopropyl alcohol seems to be a good bet, though.
It also evaporates quickly, leaves nearly zero oil traces, compared to ethanol, and is relatively non-toxic, compared to alternative solvents.
To answer your more generic "bonus" question:
which property of a chemical would make it 'permanent' in terms of markers?
- The ink needs to waterproof, i.e. not water soluble
- The solvent needs to vaporize quickly
Regarding the bonus question: Permanence will depend on resistance of the resin to water and solvents, which may be obtained using a resin that self-crosslinks at room temperature. Alkyd paints contain this type of resin, but there are many other possibilities. You also need to protect the bond between resin and substrate, which gets tricky, because of so many possibilities for the substrate's chemical structure -- relatively easy to stick to wood or acrylic, but hard for polyolefins, especially if fluorinated. An ideal resin would be of low molecular weight and a good solvating power for the substrate, so it would penetrate somewhat into the surface, and then chemically attach as well as self-crosslinking.