Uranium glaze was the thing in the 1920s and 1930s. It gave tiles a bright, shine. It is thought that 25 percent of homes built between 1920 and 1940 came with radioactive tiles in the bathrooms and kitchens. You have an old house? Get a Geiger counter and check it out.
Uranium Glaze William Lawrence Sr Omnibit 10-23-18
Lest people become terrified now by yet one more thing in their daily lives, though, consider this last line of the article:
“In most situations, the radiation exposure is not excessive, but there are some exceptions in which pure uranium oxide [which produces red-orange coloration as a glaze] on bathroom floors can pose a hazard for infants crawling around for hours on end, day after day.”