I’d contest the statement that “less than the normal background radiation you get from rocks and stuff”. Go find a Geiger-Mueller counter and aim it at a red Fiesta plate. We did a whole undergraduate lab on exactly that-- figuring out (quantitatively, by counting statistics) whether a source was more radioactive than the background. Our orange Fiesta plate was a significantly higher source (of course, that in itself doesn’t mean it’s dangerous to be around the plates-- we didn’t compare our readings with any safety standards).
The company officials may dispute that it’s dangerous to eat off the plates, even acidic foods, but they have a responsibility to their company. I’d be interested in hearing about an independent investigation.
The reason I looked up the subject on Straight Dope is that not too long after that physics lab, a couple of us geeks ordered a pizza at Dave & Buster’s, and the pie arrived with a stack of Fiesta plates, one of which was pink. (Quick, to the Batcave!) We snickered about warning the waitress, but it would be nice to know how well that old glaze holds up under restaurant-strength usage.
It’s the pre-war orange fiestaware that’s really hot. They changed the formulation in later glazes. I took a nuclear science course in high school (it was an experimental program being tried at a small number of high schools). My grandmother had some of the stuff, and I remember we checked it out. I can’t remember the figures we got, but I DO remember it was radioactive enough that it technically belonged stored in a vault according to the guidelines we had been given. And I used to eat cereal out of those orange bowls at my grandmother’s house.
This link has a picture of one of the plates, about like her’s. They are claiming 20 millirad/hr right at the surface of the dish, which is significant:
I should note that mR should mean “milliroentgen” if he is abbreviating the unit correctly, whereas the other guy is quoting millirads. A roentgen is a measurement of energy produced in dry air by a level of gamma or X-ray radiation specifically, whereas rad stands for “radiation absorbed dose”, and indicates an attempt to account for the absorption rate in a particular material, and for different types of radiation. For a discussion like this, they can be assumed roughly equivalent.
I used to drink tea out of beige ones at my grandmother’s house. (We did have a beige one in the lab for a different part of the experiment, although it wasn’t as radioactive as the orange one.)
I really should go back and compare the data I got with some safety standards. The Frinky part of me wants to take the portable GM counter to Dave & Busters. (“Oh, I spilled root beer on my glaven…”)
(We did have a beige one in the lab for a different part of the experiment, although it wasn’t as radioactive as the orange one.)