Chalkboard Cleaner Revisited
Don’t do it! Furniture polish will eventually stain your chalkboard so much that the chalk won’t write on it. The chalkboard coating is actually a microscopically rough surface that scrapes off a little chalk every time you write on it. When you wipe off the chalk dust with an eraser, or even with water, you don’t “fill up” the texture. The oil in the polish will, and will make the bumps so slick that they won’t scrape off the chalk. I was even told (decades back when I started teaching) that you need to “re-season” the chalkboard even when you just wash it with water.