According to Wicker Paradise, you can use polyurethane to protect your outdoor furniture. Make sure to buy a polyurethane that is recommended for outdoor use so that the gleaming finish you long for will stand up well to sunlight, moisture and temperature changes.
Clean the wicker furniture thoroughly with a sponge and mild dish soap mixed with warm water. Wipe the furniture dry with a piece of cloth.
Apply the polyurethane in a thin coat, keeping the brush at a right angle. This will help to spread out a thin layer on the furniture. Thin coats are recommended for polyurethane because it dries up to a very hard finish. A thick layer can be overly brittle, which can result in cracking.
It is recommended to carefully inspect the furniture to make sure that you have covered the wicker, especially around corners and near the seams. Let the polyurethane dry thoroughly. Make sure to check the label on the can for guidance. The drying can depend on the climate and humidity and it may take between 6-8 hours,.
You can touch any part of furniture the bottom of a table or chair leg, to ensure that it is dry. If it is sticky, give it more time to dry. Once it is completely dry, apply another thin coat of polyurethane. Finally, give your newly protected wicker furniture plenty of time to dry and cure before using it.