Hobbies And Interests
Considerations
Both tung oil and boiled linseed oil come from plants. Tung oil comes from tung oil trees, while linseed oil originates in the flax plant. Linseed oil is a less expensive alternative to tung oil, although tung oil may stand up better over time in some applications. Linseed oil can build up on a surface and give it a yellow tint, something that may not show on darker rocks. Light rocks, however, could discolor. Tung oil also provides a more elastic finish and is less likely to disintegrate over time, unlike boiled linseed oil. Boiled linseed oil has driers in it to speed its drying time, while raw linseed oil may take too long to dry, especially on dense rocks.
Application
Both oils are easy to apply using paintbrushes or rags. Rocks generally have irregular surfaces, which could be difficult to roll evenly with a paint roller. Many containers used for tung or boiled linseed oil have small spouts, which necessitates pouring the oil into a jar or can that the brush fits inside. Before applying the oils to the rocks, brush the rocks to remove dust and debris. The rocks should also be dry before coating. Porous rocks or sedimentary rocks absorb oils quickly, while dense rocks do not and require longer drying times. The application may need to be repeated three or four times for both types of oil.
Benefits
Coating rocks with natural oils to seal them versus using synthetic sealers like shellac or varnish has several benefits. The oils release no volatile organic compounds, which can irritate the respiratory track. The oil coatings never crack, and sunshine does not degrade the finish. It's easy to freshen these oil finishes by re-coating them without having to sand or strip the previous surface, as you often have to do with synthetic sealers.
Warning
Rags and brushes can spontaneously combust when using any kind of linseed oil, whether it's raw, boiled or an ingredient in other finishing oils. After using a brush or rag with linseed oil, soak it in a bucket of water or wash it thoroughly with soap and water to remove the threat of combustion. Tung oil contains nut oils, and anyone who is allergic to any kind of nut needs to use care when using tung oil for sealing purposes.