My "fingernails on a chalkboard" is unglazed pottery. Even just skimming this thread makes me shiver. Next restaurant in Chicago has some unglazed dishes in their collection, and my customer profile now includes "no unglazed dishes" along with my bell pepper sensitivity. The first time I got a dish served on one of those plates, there was an artistically placed sauce that would have required me to scrape my fork over the plate...I had to ask them to replate it for me. I can't touch it and I definitely can't stand the sound of pieces of unglazed earthenware touching one another. Ugh, even just writing this is making my skin crawl. Needless to say, no earthenware cooking pots for us!