Old Fiesta dinnerware was made using radioactive glazes. While the red pottery is noted for its especially high radioactivity, other colors emit radiation. Also, other pottery from the era was glazed using similar recipes, so just about any pottery from the early to mid 20th century may be radioactive. The dishes are highly collectible, both because of their vivid colors (and because the radioactivity is cool.) But is it really safe to eat off these dishes or are they best thought of as decorative pieces to be admired from afar? Here's a look at just how radioactive the dishes are today and the risks of using them for serving food.

What's In Fiesta That's Radioactive?

Some of the glazes used in Fiesta Ware contain uranium oxide. Although several colors of glazes contain the ingredient, the red dinnerware is best known for its radioactivity. The uranium emits alpha particles and neutrons. Although the alpha particles don't have much penetrating power, the uranium oxide could leach from the dinnerware, particularly if a dish was cracked (which also would release toxic lead) or the food was highly acidic (like spaghetti sauce).

The half-life of uranium-238 is 4.5 billion years, so you can rest assured pretty much all of the original uranium oxide remains in the dishes. Uranium decays into thorium-234, which emits beta and gamma radiation. The thorium isotope has a half-life of 24.1 days. Continuing the decay scheme, the dishes would be expected to contain some protactinium-234, which emits beta and gamma radiation, and uranium-234, which emits alpha and gamma radiation.

Just How Radioactive Is Fiesta Ware?

There is no evidence that the people who made these dishes suffered any ill effects from exposure to the glazes, so you probably don't have a lot to worry about by just being around the dishes. That being said, scientists at Oak Ridge National Laboratory who measured radiation from the dishes found that a standard 7" "radioactive red" plate (not its official Fiesta name) will expose you to gamma radiation if you're in the same room as the plate, beta radiation if you touch the plate, and alpha radiation if you eat acidic foods off the plate. The exact radioactivity is difficult to measure since so many factors play into your exposure, but you're looking at 3-10 mR/hr. The estimated daily human limit rate is only 2 mR/hr. In case you've wondered just how much uranium that is, researchers estimate a single red plate contains approximately 4.5 grams of uranium or 20% uranium, by weight. If you eat off the radioactive dinnerware daily, you would be looking at ingesting around 0.21 grams of uranium per year. Using a red ceramic teacup daily would give you an estimated annual radiation dose of 400 mrem to your lips and 1200 mrem to the fingers, not counting the radiation from ingesting uranium.

Basically, you're not doing yourself any favors eating off the dishes and you certainly don't want to sleep with one under your pillow. Ingestion of uranium could increase the risk of tumors or cancer, particularly in the gastrointestinal tract. However, Fiesta and other dishes are a lot less radioactive than many other items produced during the same era.

Which Fiesta Ware Is Radioactive?

Fiesta commenced commercial sales of colored dinnerware in 1936. Most colored ceramics made prior to World War II, including Fiesta Ware, contained uranium oxide. In 1943, manufacturers stopped using the ingredient because the uranium was used for weapons. Homer Laughlin, the maker of Fiesta, resumed using the red glaze in the 1950s, using depleted uranium. The use of depleted uranium oxide ceased in 1972. Fiesta Ware manufactured after this date is not radioactive. Fiesta dinnerware made from 1936-1972 may be radioactive.

You can buy modern Fiesta ceramic dishes in just about any color of the rainbow, though the modern colors won't match the old colors. None of the dishes contain lead or uranium. None of the modern dishes are radioactive.

Sources

Buckley et al. Environmental Assessment of Consumer Products Containing Radioactive Material. Nuclear Regulatory Commission. NUREG/CR-1775. 1980.

Landa, E. and Councell, T. Leaching of Uranium from Glass and Ceramic Foodware and Decorative Items. Health Physics 63 (3): 343-348; 1992.

National Council on Radiation Protection and Measurement. Radiation Exposure of the U.S. Population from Consumer Products and Miscellaneous Sources. NCRP Report N0. 95. 1987.

Nuclear Regulatory Commission. Systematic Radiological Assessment of Exemptions for Source and Byproduct Materials. NUREG 1717. June 2001

Oak Ridge Associated Universities, Fiesta Ware (ca. the 1930s). Retrieved April 23, 2014.

Piesch, E, Burgkhardt, B, and Acton, R. Dose Rate Measurements in the Beta-Photon Radiation Field from UO2 Pellets and Glazed Ceramics Containing Uranium. Radiation Protection Dosimetry 14 (2): 109-112; 1986.

Vaughn Aubuchon (2006). Geiger Counter Comparison - Popular Models. Retrieved April 23, 2014.