Porcelain has been in use in the U.S. since the 1890s. Porcelain signs have become a highly collectible item because of their bright colors and interesting graphics. Some porcelain signs, if they are in good condition, can be worth quite a lot of money. At one time porcelain signs were not difficult to find, but many have been destroyed or are in collections. While it can be tempting to use heavy-duty cleaning solutions on your porcelain sign, simpler cleaning solutions will work better.
Pour 1/2 cup baking soda and warm water into a spray bottle. Screw on the cap and shake to mix.
Spray the baking soda and water solution liberally on the porcelain sign.
Use a soft cloth to lightly rub the baking soda and water onto the sign. Start from the top and clean your way down the sign. If the sign is particularly dirty or if the baking soda and water start to dry, spray more of the cleaning solution on the sign.
Rinse the sign well with warm water. You can dip the sign in water or use another spray bottle filled with plain water to rinse the sign.
Mix one part bleach with one part water in a clean spray bottle. Spray the bleach solution directly onto the sign and allow it to sit for just a few minutes. Rinse well with water, and repeat if the sign has stains. The bleach solution whitens white porcelain and brightens colored porcelain.