Although more time-consuming for the teacher, teaching with blackboard and chalk has repeatedly proved to be a suitable instrument for regulating working speed and ensuring clarity. It is assumed that the speed of writing on the blackboard corresponds to the speed of thinking, i.e. the speed of taking in, processing and understanding. The process of recording on the board, the decision as to whether and what of what is written on the board is noted down and writing it down already contributes to anchoring in the brain ("from the hand to the head").
Working on the blackboard is seen as a regulator for the speed of work in the course. While writing on the board, students can think through the facts presented, take notes or make notes.
In addition, facts can be outlined, questions discussed or models developed on the blackboard, step by step, in small sections and clearly. Short texts ensure that the key findings are retained. The blackboard follows the course of the lecture and documents/saves it for several minutes, half an hour or even the entire time.
For geology enthusiasts, the blackboard chalk can also be used as a test object, e.g. for a lime test with hydrochloric acid.