Watches are an essential, if overlooked, piece of modern machinery. Most watches are designed to have some degree of water resistance; however, few watches are completely waterproof. Condensation, or fog, forms on the inside of a watch face for a number of reasons. It could be from a faulty seal or from water droplets that form on the exterior surface of the watch face and cool the air behind it. Whatever the cause, it is necessary to remove the moisture from inside the watch face to prevent damage.
Place the watch on a towel. Use the screwdriver to remove the back of the watch. Some watches require a watch case wrench to open the back.
Set the hair dryer to "low" and blow warm air over the open watch case in a sweeping motion. Do not blow a direct stream of air into the watch or it could get damaged. Blow-dry the watch in this manner for 10 minutes.
Move the towel and the open watch to a sunny windowsill or other warm, dry place. Allow the watch to air-dry for 24 hours. Replace the case on the back of the watch.