what kind of paint would be best to use - I am talking about a knife rack I need to change its colour - (please dont argue with me about that )
would paper be less problematic?
magnets work through magnetic fields. Paint will do nothing to stop the magnetic field from attracting objects. The only way to limit the field is by breaking the magnet or keeping objects out of the field or using any field to disrupt or alter the field. See that the earth is itself a magnet!
Answer is no. But if the coating of paint is thick it could allow the knife not to stick as well but the magnet still has all its power. If you want to test, take a piece of black electrical tape, and tape it to the magnet. If the knife still sticks ok then you are ok to use paint up to that thickness of the tape. Of course remove the tape, it was only for a test. The tape will make the magnet appear not to be as powerful as the knife cannot get as close to the magnet. Same as if you use a very thick enamel paint. My guess it will still work fine. What kind of paint to use? No lead paint! as you are dealing with food. Read and checkout first before you apply any paint to see if it safe around kids and food.
No, it will have such a small effect, if any, that it will not be noticable. Remember what a magnent is. It messes with magnetix, it doesnt blow air. It also does not require a medium in witch to work, so paint away!