We usually try to clean them with a cloth and water but avoid to scrub. If they are more persistent stains, we usually use glass cleaner or dishwashing liquid. Of course we recommend avoiding stronger cleaning liquids such as grease remover, since rubbing a lot ends up lifting the ink.
First of all, we recommend avoiding all types of abrasive liquids, such as alcohol, acetone, solvents, white spirit, etc. as you will damage the quality of the material.
Unfortunately we can only accept exchanges or returns of products that have not been used, and they must be intact as they were sent. You can read our exchange and return policy for more information.