Oil spill cleanup seems to be the problem with a former printing company floor that will not clean. Technique now involves applying a combination of odorless paint thinner, laundry soda and Pine Sol in hot water with damp mop. Oily gunk rises to surface in a milky emulsion. Rinse black gunk from mop repeatedly. Dry with paper towel (or other cellulose product). Result is sticky, black floor. Don't know if this is an improvement.