What kind of board chalk is this?

daveyp225

In the following MIT video, some kind of thick chalk (not sidewalk, already tried it) is used in the lecture:

http://ocw.mit.edu/courses/mathemati...ture-2-limits/

It looks like great chalk. Or what chalk is this easy to write with?

Pythagorean

didn't look at video, but:

http://www.amazon.com/Liquid-Chalk-B.../dp/B004IM79HI

coffee shops use this kind of chalk a lot because it allows them more control when drawing pretty menus on blackboards.

daveyp225

Thanks for the suggestion. I have to erase a board probably 10 times a lecture, so wiping it down with water will not work well for me.