I make a homemade rub that we just love for prime rib like for on the 35 day Drybag aged one that is for supper tomorrow night. I make it in small batches, but there is always a goodly bit left over so I save it in a tightly sealed glass spice jar from Penzkys. Then when I make a new batch I mix in the leftover which always is just a tad clumpy by then. I have been thinking that maybe I should add some anti-clumping agent to prevent that. Would common corn starch work? OTOH since I assume the clumping comes from the presence of moisture would merely adding some dry white rice to the stored rub do the trick and not add any taste?