We made for our museum a video of the champleve enamelling technique by Michele Gilbert, Limoges, France
The artist is using a black resist - it is an oil based product that requires time for drying - smells real strong-and resists the acid etching - It can be purchased through Thompsons or any other enamel supply store. The dried tiles are then attached to duct tape or any heavy duty tape and laid into the acid bath for etching.