I am starting to clean the studio up for the next round of creating and scraping shelves is something I do not enjoy. I read this tip in a magazine a while back so unfortunately I can't give kudos to the person who wrote it but before my last glaze firing I sprayed some water on my pristine new shelf (that I bought because some of my old ones are so crusty) dusted it with alumina hydrate and then misted with more water. Put it in the kiln loaded pieces glaze fired and it was awesome!!! Nothing stuck at all! In the past I have had the black underglaze that I sign my name with stick to kiln wash. Sometimes I also do little drawings and the bottoms and certain colors would stick but not this time! Then I laid out newspaper and just dusted the shelve off and am going to reuse the alumina. If you have never tried this I highly recommend it.