[procaryote]

If you leave writing on a whiteboard too long water won't do the trick and you'll need something stronger, like isoproplanol, or one of the many purpose mixed cleaning sprays

"chemicals" isn't inherently bad of course, if that needs saying. Don't drink the cleaning spray and you'll be fine

[readthenotes1]

My experience was that once you use something more stronger than water, you have to continue using that substance.

Alternately, whatever chemicals are in the marker ink will dissolve previous marks and leave the whiteboard surface intact. Just right over what was written before and it will melt