The blackboard is clearly black, why is it green?

       Recalling the scene in the classroom, you saw yourself sitting on a brown chair, with textbooks and stationery on a brown wood grain table. Then you looked up and saw a dark green blackboard in front of you... and so on! The blackboard is clearly black, why is it green?

When I was studying before, I used to sit in the classroom and think about a question - why does the teacher always say please look at the blackboard, but that board is green? Is there any misunderstanding among them?

In fact, in the early 19th century, people used large stone slabs connected together to make blackboards, allowing teachers to write on them for the whole class to see. The name "blackboard" only appeared in 1815. In the 18th century, because paper and ink were relatively expensive, cheap and durable erasable stone slabs became a substitute.

At that time, students would bring a black slate to class, and these "small blackboards" were the predecessors of the large blackboards in the classroom. Therefore, in the beginning, blackboards were indeed all black, and they were made of slate. In rural areas, the raw material for blackboards was wooden boards. People mixed egg whites and roasted potatoes together and painted wooden boards dark. Later on, blackboards were all made of wooden boards, and the blackboards at that time were not adulterated with fake ones.

Until the 1960s, in order to reduce transportation costs, manufacturers changed the material of blackboards, replacing black slate with green coated steel plates. The new material was lighter and stronger, and chalk marks were easier to erase.

Why use green? Because green is not easily reflective, and it can relax the eyes. Even if you look at it for a long time, the eyes are not easily tired. For teachers who stare at the blackboard all day long, green blackboards are softer in color and more eye friendly, so "real blackboards" are gradually replaced by green blackboards. Therefore, most blackboards have been changed to "green boards", but the names have not been intentionally changed.

The editor has something to say:

As a familiar memory of our childhood learning, the blackboard also had such a birth process. Today, the editor has gained some insights. With the development of the times, blackboards have gradually been replaced by various multimedia projectors. However, in my opinion, the green color in the classroom still has a learning flavor and will always be an irreplaceable warm color in our memory.