Spar urethane is a protective clear coat finish that has been specially formulated to use on interior or exterior wood surfaces exposed to water, sunlight, or changes in temperature. The UV blockers contained in spar varnish, help to reduce the effects of fading or graying caused by the sun. The basic difference between other varnishes and spar, is the ratio of oil to resin. In spar, this ratio is relatively high, which makes for a more flexible finish. It is tougher than polyurethane, making it more resistant to cracking and chipping. This also makes it more durable under dramatic temperature changes.

Big fishing boat
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Spar urethane is suitable for finishing boat decks.


The protective barrier spar urethane forms against moisture makes it a perfect choice to use on exterior wood surfaces. It has the ability to expand and contract with the wood during seasonal and temperature changes. It's also good to use on some interior surfaces. The recommended items spar urethane can be used on are: boats, outdoor furniture, doors, bathroom and kitchen cabinets, kitchen counter tops and windows. It is not recommended to use spar urethane on interior wooden floors.


The sheens available are: gloss, semi-gloss and satin. When using spar urethane it is recommended to wait at least four hours before re-coating and waiting twenty fours hours for it to completely dry. Spar urethane is produced by several manufactures and you should be able to find it at hardware or paint stores. You can purchase it in quart, gallon and five-gallon containers.

Application Steps

Spar urethane should be applied with a natural bristle brush. Make sure your work area is as clean and dust free as possible. Any wood surface you are working on should be dusted off with a lint free cloth before application of spar begins. It is recommended that to mix the paint you should do so by stirring and not shaking. If you shake the can to mix the contents, air bubbles will form and remain in the paint surface. You can clean up spar urethane by using mineral spirits.


Make sure you are working in a properly ventilated area when using spar urethane. Safety glasses and vinyl or rubber gloves are also recommended, in case splashing occurs. Avoid using spar urethane around extreme heat or sources of ignition. The effects of overexposure are: acute nausea, dizziness, respiratory tract and throat irritation. Consult medical attention if conditions grow worse. There are no long term effects that are known from exposure to the chemicals in spar urethane.


If you have wood items that are being exposed to sunlight and nature, consider painting them with spar urethane. It's ideal to protect wood facing tough environmental conditions. Not only will it protect the wood, it will also extend the life and the beauty. Spar urethane is not cheap, but it's a great investment for wood you'd like to last and keep in top notch shape.