Getting rid of water chalk

This is in the context of a blackboard. I have used a water chalk stick to write on it and I can't get it off. I have tried industrial hand wipes which can remove just about everything from everything but it has not touched it at all.

Is that like indelible pencil?

It looks like a piece of chalk, but not dusty like chalk. It will write on glass like car sales places do. I am going to try meths next and then white spirit after that I am out of ideas.

Googling liquid chalk found a lot of people asking the same question...
Answers were generally try these, in this order, and for the latter ones, be prepared to repaint the board if it damages the surface:
- water and detergent
- window cleaner
- non-acetone nail polish remover (ethyl acetate)
- Chalkboard Magic-Shadow Killer Sponge
- magic eraser

meths worked a little but also took off the black paint as well.

I am guessing repaint the flamin board and use ordinary chalk afterwards is about the only real solution grrrr!

Yes - infuriating!

I like the sound of the Shadow Killer Sponge though![]