I always wondered how my parents were able to learn by writing with their pencil on their slate, wiping it off afterwards and writing the next thing on it. Seem

I always wondered how my parents were able to learn by writing with their pencil on their slate, wiping it off afterwards and writing the next thing on it. Seems comparable to me. https://de.wikipedia.org/wiki/Schreibtafel#Schiefertafel https://de.wikipedia.org/wiki/Schreibtafel#Schiefertafel