Orton Foundation Firing Tips: Making Food Safe Ware

When making ware to contain food and beverages, it is very important to be sure it is food safe. Some of the important considerations for mugs, serving pieces and dinnerware include:

Clay body composition · Design of the ware · Glaze selection · Decoration · Firing to maturity · Testing for lead safety · Government regulations

What Type Of Ware?

Careful shape design is important for food and beverage containers.

Design-related cracks, rough areas, crevices and nooks and crannies are difficult to clean and might trap bacteria. They can also be difficult to thoroughly glaze. Pitchers with hollow handles can have problems.

Ware also needs to be serviceable. That is, it should be strong so it won't fail or break during service.

Making Smart Glaze Choices

While glazes are extremely durable, most are not completely insoluble. If attacked by acids in foods such as orange juice, vinegar and tomatoes, small amounts of the glaze may dissolve and pose a health hazard.

Acid resistant glazes have passed rigorous tests and are labeled as food safe. These should be selected for glazing food ware. Lead-free glazes may not be acid-resistant and should not be used unless labeled as food safe.

Crackle, matte or specialty glazes also should be avoided for surfaces of containers that will contact food and beverages.

How To Decorate

When glazing lowfire, be sure to completely glaze the ware to ensure the entire body is sealed. Properly bisqued porcelain may be dry footed, but only if the porcelain has been fired to vitrification. Stoneware is usually dry footed.

China paints, decals and rim designs are a popular way to decorate plates and mugs, but may not be safe for food surfaces. Specific regulations exist for the location of rim decorations which must be followed.

Decals should be used on the outside of a piece where they will not be in contact with food or beverages. Use china paints on decorative items only.

Safe Firing

Proper glaze firing and the bisque firing are very important to insure ware is food safe. If the bisque is under fired, it may create problems with glaze and body fit that result in crazing of the glaze, or glaze surface defects such as pinholes. These would not be acceptable for ware used to contain food and beverages.

If the glaze is not properly matured, it will not meet the food safe standards under which it was tested and may craze while in service.

Using pyrometric witness cones on the kiln shelf is the only way to insure that a proper firing has occurred. For food safe poured ware, many prefer to fire their bisque to an 03 witness cone just to be sure it is fully mature. Read the manufacturer's instructions.

Regulations

There are several very specific regulations for ware which will contain or contact food and beverages. California has the most stringent rules for dinnerware and new standards have been set by the FDA for clay decorations. These rules are available from standard federal agencies. If you are selling your dinnerware you may be subject to additional regulation.

How To Test For Lead Release

Several easy to use products are available on the market to test for lead release. These are primarily quantitative tests-that is, they tell you yes or no if the surface has lead above a certain level. The most commonly used kit is a thick cotton swab which turns pink if lead levels are exceeded. This test does not harm ware so if it tests too high in lead, the piece can still be used as decoration. These tests are a simple, economical way to feel confident that your ware is lead free and safe.

Reprinted with permission from Orton Foundation

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