How to Make a Blackboard
1. Choose a support medium. Any surface that is firm enough to support chalk writing can be used for a blackboard.
2. Prepare the surface. In the case of wood, sand the side you plan to use as a blackboard to the degree of smoothness you desire. The smoother the surface, the smoother the chalk lines.
3. Apply blackboard paint. Apply even, thin coats with a roller. Apply additional coats after each coat has completely dried.
4. Cure. Although a coat dries in about four hours. Your blackboard will need at least three days to fully cure and be ready to work with. So factor that into the plan.
5. Condition. If you apply chalk to an unconditioned blackboard either you will have difficulty getting the chalk to adhere to the board or what does adhere will never fully erase. Chalk adheres to the chalk dust on the surface of the board; not the board itself. To condition the board, gently rub a piece of white chalk over the entire surface of your blackboard and then erase. Once conditioned, your blackboard is ready to use. No go forth and create.
A Few Notes:
Let how you plan to use your blackboard drive the smoothness of your surface. For example, I draw on my blackboards. And I love the unique texture that wood grain creates on chalk lines; so I’m using a 24” x 24” panel of plywood.
To prime, or not to prime, that is the question. Whether or not to prime depends on the support medium, how many coats of paint you plan to use and how you plan to use your blackboard.
When I work on painted wood, I often use a lot of pressure. And sharp chalk edges can cut into the wood. This is why I use six coats of paint on the drawing surface and two coats on the back of the panel.
When I've used primer, I've used two coats of primer and four coats of blackboard paint. Either way works for me.
I paint the entire panel to seal and protect the wood. (And also the back isn’t sanded to with less paint I can easily tell one side from the other by feel.) Apply even, thin coats with a roller. Apply additional coats after each coat has completely dried.
You can make your own chalkboard paint if the ready-made options do not suit your needs.
Yes, you can over-condition. But, no worries, you can always erase away the excess chalk dust.