When I was a mechanic a customer came in with a vehicle that had brand new tires on them. He asked us if while we were servicing it we could remove the blue protective coating on the white walls. I guess whoever installed them forgot.
Well me and the other guys tried everything. From soapy hot water to brake kleen. Those who have experience with brake kleen know how good it is at removing stuff.
My boss comes out and asked us what we were doing. After a quick explanation to him he then took out a clean rag, dipped it into his black coffee and to my amazement he wiped away the blue protectant without effort.
After that I realized the cleaning prowess of coffee