That's due to the oil barrier. I like that idea, wish I'd considered it!! Even so, that's, I now 3D print cat food bowls that have an extremely small, canted inward oil ring, which stops kittie's fur from accidentaly having oily. It works very well and is simple to wash. https://jaspervqmgb.nizarblog.com/36516832/examine-this-report-on-pet-store-jlt