What is happening to this pyrex? Is it safe to use?
This pyrex measuring cup is completely clean, just freshly taken out of the dishwasher. I also use in in the microwave sometimes. Have had it for many years, to my knowledge. Seems like a coating is coming off, but what is it and why?
The bottom of the cup says "516, T.M.REG, PYREX (all capital letters), U.S.PAT.OFF., C -S, for general household and photographic use only"
ETA: Deep cleaned my dishwasher last month. Whatever is happening to the Pyrex doesn't wash off with bar keeper's friend, which usually works great on soap scum for other items. I've tried to hand wash it with BKF without any of it coming off. Scrubbing and soaking with vinegar also doesn't work. And no other dishes show any sign of soap scum.
Thanks in advance for any insight!
ANSWER: just etching damage caused by putting in the dishwasher & it is safe to use. Yay!