Never seen pure tung oil mold. Heck the Song Dynasty in china where tung oil first came from used the oil to waterproof ships.
Pure Tung Oil was and is one of the first truly “Green” finishes. It is all natural and contains zero VOC’s. Pure Tung oil (China wood oil) is an all-natural finishing product that provides a tough, flexible and highly water-resistant coating or wood finish. It is classed as a drying oil along with linseed, poppy seed, safflower seed, walnut, soybean, oiticica and a few other oils. Although it is relatively new to the Western world, tung oil also known as chinawood oil has been known for centuries to the Chinese, and until this century, China was the main source for the oil. It comes from the seed of the tung trees, Aleurites fordii and Aleurites montana, deciduous trees that are very susceptible to frost damage. This vulnerability has restricted the cultivation of the trees to China and South America. Tung oil (china wood oil) received wide application in China: in the building trades as a treatment for both stone and wooden structures; in marine trades as a preservative and water repellant on wooden boats. It is said to have been introduced to the West by Marco Polo. From the 13th to the 19th century, tung oil had only limited use in the West. More recently, it’s gained favor over linseed oil for wood finishing because it is faster drying and does not darken as much with age.