That's due to the oil barrier. I like That concept, wish I had considered it!! Having said that, that's, I now 3D print cat food bowls that have an exceedingly small, canted inward oil ring, which prevents kittie's fur from accidentaly getting oily. It works rather well and is simple https://bird-food08641.blogripley.com/37106627/pet-corner-dubai-an-overview