Painting a coffee cup is a project that adults and children can do to add instant personalisation to a mug for a gift or to have at home as a special mug. However, not all paint applied to coffee cups is waterproof. The best way to make a painted coffee mug waterproof is to paint the design with air-dry enamel paint and paint over the design with an enamel glaze after the paint dries. You can add enamel glaze to coffee cups painted with another non-washable paint as well to make that paint waterproof and durable.
Wipe the mug clean with a soft, damp cloth. Take extreme care when wiping the mug so that you do not damage any part of the paint, which may be delicate.
Dip a sponge brush into ceramic enamel glaze. Use a high-gloss glaze for a shine, or a satin glaze for a reduced shine. Gently coat the entire exterior of the mug with the glaze. Allow the glaze to dry for two hours, or until the glaze is dry to the touch.
Apply a second coating of glaze over the painted area of the mug. Allow the mug to dry in a cool, dry area for 10 days before using or washing the mug.
Wash the coffee mug in hot water with dish soap. Allow to dry for 24 hours before painting.
Dip a sponge brush in ceramic surface conditioner. Wipe the area of the mug that you intend to paint with the brush. Apply a thin coat of conditioner. Allow to dry for 24 hours.
Paint the surface of the cup with air-dry enamel paints. Allow the paint to dry 24 hours until it is dry to the touch.
Paint the design with an enamel air-dry glaze to add additional protection to the surface of the mug. Glaze the painted design and 2 inches beyond the design on all sides. If you painted over the entire mug, then glaze the entire mug. Allow the mug to dry for a full 10 days before using or washing the mug.