How can I clean my blackboard?

as far as i know you can't. i tried with mine without positive results. i become familiarized with you because almost all your posts are related to problems. i think i'd like to talk to you some time. i dont think you cant speak without talking about problems. sorry, but it is funny to me. i appreciate you only ask about technical problems, not metaphysical ones, like many here. at least, yours may have an easy solution. i hope.