However, is liquid chalk really a good substitute for traditional chalk when used on chalkboards?
Many liquid chalk pens are water-based, and claim to be erasable. But this is mostly true only when they are used on certain non-porous surfaces like glass or on this chalkboard surface.
Instead, when such liquid chalk pens are used on traditional chalkboard surfaces, they tend to be very difficult to erase and often leave permanent marks.
Indeed, the internet is replete with reviews and complaints of unsuspecting consumes who used liquid chalk pens on their chalkboards thinking that the writings were erasable, and then had trouble erasing those writings (see this and this).
So, always be very careful when using liquid chalk pens on your chalkboards. Use them sparingly, or only if you do not intend to erase them later =)