How Does a ‘Blackboard’ Work Without Paint?

A blackboard works like a magic wall that can remember what you write. It’s made of a special kind of stone called gypsum, which feels smooth and soft. When you write on it with chalk, the chalk sticks to the stone, but when you erase it, the chalk just slides away, leaving no mess behind! It’s like drawing in sand and then wiping it clean.

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Examples

Drawing on a blackboard is like drawing on a smooth sandcastle, you can erase it as easily as you built it.
A teacher writes a math problem on the board, then wipes it clean for the next lesson, just like magic!
You write your name with chalk and then erase it so someone else can write their name too.

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Categories: Technology · blackboard,technology,materials science