The thickness of the coating will depend on your desired application. For our hard coat products, we typically recommend applying a minimum of 60 mils to create a uniform film that will protect the piece. For more demanding applications where high impact is expected, such as outdoors, we recommend applying 60-120 mils to achieve the best results. Our brushable coatings have the best success at 100 mils and greater. The machinable hard coat should be applied thick enough that when machined, it is not reduced to less than 1/8 of an inch.