What are the disadvantages of using blackboard?

Blackboards, or chalkboards, are made out of temporary materials— normally dark gray or black slate stone sheets — that do not last very long, and are always fixed, restricting the use of classroom space and creating problems for those who have vision impairment. Blackboards become cloudy and chalky after some time with the usage of certain kinds of chalks and improper cleaning practices.

The highest grade of blackboards are made out of rough versions of porcelain enameled sheets. However, they are still messy and difficult to use. Also, they are fixed at a certain height that is not always comfortable for all users.