Q: Were blackboards originally made of smooth? ¶
A: Yes, and thin sheets of black or dark grey slate stone.
Q: Are blackboards made of a rougher version porcelain enamelled steel? ¶
A: Yes, Porcelain is very hard wearing and blackboards made of porcelain usually last 10–20 years in intensive use.
Q: Are blackboards difficult to date? ¶
A: Yes, but they were used for music education and composition in Europe as far back as the sixteenth century.