That is because of the oil barrier. I like That concept, want I had thought of it!! However, that may be, I now 3D print cat food bowls that have a really compact, canted inward oil ring, which stops kittie's fur from accidentaly getting oily. It really works really well https://cat-toys77665.blog-ezine.com/36509160/examine-this-report-on-pet-store-jlt