is applied with a process called French polishing. The wood itself is polished and hardened as the oil is saturated into the surface. I usually apply about 20 coats or more of tung oil allowing each coat to soak in and cure in between each coat. The oil I use now is 100% pure tung oil, thinned with 100% pure citrus solvent. The oil is used with 600 up to 1200 grit sand paper to hand polish. then i will keep applying thin coats once a day until the surface is saturated with oil and polished. The time it takes, which varies depending on the wood used, temperature and humidity, carvings and intricate scrolls add to the time frame. The process takes several weeks as a minimum though i often will add more. The more time I have the better the finish will be. I have experimented with many different types of finishes over the years and now i like Tung Oil the best for it is the most durable and looks the best after years of playing and feels the best while your playing. I am also using violin varnish on spruce tops and softer woods.