Many materials only seem nonporous but they are actually slightly porous and that can cause some problems when erasing chalk ink.
That's why we always recommend testing each surface before use.
- Make a small dot on a inconspicuous area and wait until ink dries.
- After some time try to erase the ink with dry or damp cloth.
- If the ink can be fully erased without leaving shadows or ghosting behind, you are free to use Blami chalk markers on that surface.