Things You'll Need
2 wide-mouth jars
Spar varnish, also called marine varnish, is a tough formula used for boats and exterior jobs. The sticky substance can ruin a good paintbrush very easily, so after finishing your job, clean your brush right away. A simple rinsing with water will not cut it; in order to remove chemicals, you'll have to use chemicals. Getting the brush clean will take a few extra minutes at the end of your work day, but a good varnish brush is worth taking care of properly.
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Brush a scrap piece of wood with the brush to remove excess varnish from the bristles. Move to a clean area of the wood every couple of strokes, to thoroughly wipe off the varnish.
Put on safety goggles and wear protective gloves to protect your eyes and hands. Work outdoors or in a well-ventilated area, away from open flames.
Fill a wide-mouth jar with benzine. Benzine is a highly flammable petroleum distillate and mineral spirit that emits toxic fumes but also cuts through varnish. Dip the brush bristles into the benzine and work them against the bottom and sides of the jar.
Remove the brush from the benzine and wipe off any excess with a paper towel. Repeat the benzine application then wipe the brush dry a second time.
Fill a clean wide-mouth jar with turpentine. Turpentine is an oil made from pine resin. Dip the brush bristles into the jar and work the turpentine into them with your fingers.
Remove the brush from the turpentine and wipe the bristles clean with a paper towel. Reapply the turpentine as needed to remove all traces of varnish from the brush.