... by special machine.3,there is a base to hold the blackboard.4,can be written constantly with a chalk.5,usually ... 2,3.Some relevant pictures for reference:Blackboard is coated on special machine:Coated blackboard machine:Test report ASTM F963-08Test report for ... more than 600 workers, specially producing different kinds of mini blackboard,chalk board, whiteboard, writing & drawing boards and color clay ...