I love this project, and if you have an unusual or fancy frame it can definitely have the WOW factor too. Scour charity, junk shops & car boot sales for cheap pictures or mirrors with great frames that you can give a new lease of life to. Once it's hanging on your wall I guarantee all your friends will want one.
1. Disassemble the frame and carefully dispose of the picture & glass or mirror insert.
2. If the backboard is missing or in poor condition use the frame or old backboard as a template, draw around it, cut a fresh backboard, sand the edges smooth & wipe with a damp cloth to get rid of any dust.
3. Optional - Place the frame on some newspaper and paint the frame (following the instructions on the tin, and applying a base coat & extra coats of paint if necessary).
4. Place the backboard on some newspaper and paint one side with the blackboard paint (read & follow the instructions on the tin), leave to dry.
5. Apply 1 or 2 additional coats of blackboard paint leaving to dry between each coat.
6. When everything is dry reassemble the painted backboard in the frame (I've fixed the frame in place with panel pins and gummed art tape).
7. Hang the framed chalkboard on the wall, stand back and admire your work.
Here's the frame before and after:
...and finally, here's an old brass mirror that I gave the chalkboard treatment to: (sorry about the fuzzy first picture.)