How To Clean A Polyurethane Brush?
QUICK ANSWER
Clean a polyurethane brush by soaking it in mineral spirits if the poly is oil-based, or warm soapy water if water-based. Work the bristles to release the finish, change the solvent until it stays clear, then rinse and air dry. Clean immediately after use, not later.
A good brush is worth saving, and polyurethane will ruin one fast if you let it dry. Cleaning it properly takes only a few minutes, but the method depends entirely on whether your poly is oil-based or water-based. Use the wrong approach and you will waste product and possibly the brush.
How do you tell oil-based from water-based polyurethane?
Cleaning method depends entirely on whether the polyurethane is oil-based or water-based. Check the can label. Oil-based polyurethane requires a solvent like mineral spirits or paint thinner because oil and water do not mix. Water-based polyurethane cleans up with warm soapy water alone. Using the wrong solvent does nothing helpful and wastes time and product. The label is the first thing to read before touching the brush. If the can is gone, smell test the dried finish: oil-based has a strong solvent odor.
How do you clean an oil-based polyurethane brush?
Pour mineral spirits into a glass or metal container (not plastic, which can react). A multi-jar method works best: submerge bristles in the first jar, work them with gloved fingers or a brush comb, then move to a second jar of clean spirits. Repeat through 2 or 3 jars until the spirits stay clear. Finish with warm soapy water rinse, then shape and air dry flat or hanging bristle-down to keep the bristles straight.
How do you clean a water-based polyurethane brush?
For water-based polyurethane, simply rinse the brush under warm running water immediately after use, working the bristles with your fingers to release the finish. Apply a drop of dish soap and scrub by hand or with a brush comb. Rinse until the water runs clear. Spin the brush between your palms to remove water, then reshape the bristles and let air dry. The whole process takes a few minutes. This easy cleanup is one of the main reasons many DIYers prefer water-based poly.
Can you save a brush that already hardened?
If you forgot to clean the brush and it has hardened, all is not lost. Soak the dried brush in mineral spirits (for oil-based) or warm water and dish soap (for water-based) for several hours or overnight. Work the bristles loose with a stiff brush or comb. Most brushes recover, though the bristles may never feel quite as soft. For very stiff brushes, a dedicated brush cleaner like Krud Kutter brush wash can rescue what mineral spirits alone cannot. Cheap brushes are not worth the rescue effort.
Match the solvent to the poly: mineral spirits for oil-based, warm soapy water for water-based. Clean while wet, work through the solvent until it runs clear, then reshape and air dry. A forgotten hardened brush can usually still be soaked back to life.
More Wood, Stain & Finish Questions
Mystery Question?
Mystery Question?
Mystery Question?