Like most of wall coverings, knotty pine may become stained from kitchen grease and years of dirty fingers. Even though you might have to sand and seal unfinished knotty pine to remove tough grease stains, you frequently can scrub them off from paneling that has a finish already implemented on it.
Vinegar and Water
Dust the wall with a microfiber cloth or wax it with an upholstery attachment.
Mix 1 cup white vinegar in 1 gallon of water. Fill a spray bottle with the solution, and shake it to mix.
Spray the walls generously with the solution and permit it to sit for 15 minutes.
Scrub the grease stain with a soft sponge, applying more detergent solution as needed.
Melamine Eraser
Dust the wall with a microfiber cloth or wax it with an upholstery attachment.
Dampen a melamine-foam eraser with water and then squeeze it out.
Scrub the grease stain with the eraser, rinsing as necessary, until the stain is gone.