Originally Posted by
ckcowl
there are a number of different chalk marking products on the market- you need to check the removal instructions for the product you used.
This is what I was going to say also. I have several different marking products and they each have do's and do not's spelled out on the packaging. When I realized that what would make one product disappear would make another product permanent, I decided to keep the packaging with each product. It's a pain, but better safe than sorry.