> [Chalkboards] look nice when they are clean, but as soon as you erase something it ends up being unreadable. Depends on what chalk you use. If you use chalk

> [Chalkboards] look nice when they are clean, but as soon as you erase something it ends up being unreadable. Depends on what chalk you use. If you use chalk from chalk (CaCO3), then yes, it's awful, but if you use chalk from gypsum (CaSO4 hydrate), it's readable on a wet board and erases well.