What is the difference between polymerized linseed oil and boiled linseed oil?

Our standard metal finish on the Pyro Tower is a polymerized linseed oil. Linseed oil is a natural product that is pressed from the dried seeds of the flax plant (Linum usitatissimum) and is commonly called flaxseed or linseed oil. The flax plant has been cultivated for thousands of years for its fiber (linen), seed and oil. Linseed oil is one of the oldest commercial oils and has been used for centuries as a drying oil in painting and varnishing.

Raw linseed oil can be used as a metal finish but it can take weeks for it to fully cure. It is for this reason that we use a polymerized linseed oil which is somewhat more viscous than raw linseed oil (making it more difficult to spread and apply) but dries considerably more quickly. The polymerization of the oil is accomplished by applying heat to the oil in the absence of oxygen. Be aware that this process produces a final product that is not the same as the “boiled linseed oil” that you might find on the shelves of home improvement and hardware stores. As counter-intuitive as it seems, boiled linseed oil has not been “boiled” or heated at all but instead has had petroleum-based solvents and metal driers added to it so that it supposedly behaves as if it was “boiled”. The most commonly used heavy metal dryer in “boiled linseed oil” is cobalt that is considered toxic. Additionally, a finish generically referred to as “Danish Oil” is produced by large paint manufacturers and contains some linseed oil but the majority of the components may be carcinogenic, petroleum-based ingredients such as Naptha, Mineral Spirits, and Dipropylene Glycol Monomethyl Ether.

Our linseed oil finish is 100% pure polymerized linseed oil that contains NO petroleum distillates, NO volatile organic compounds (VOCs) and NO heavy metal driers. The heating methods used to polymerize our linseed oil finish have been adapted from 18th to early 20th century varnish-making techniques while also using current technology and quality control measures to ensure a consistent and natural product. 

Linseed oil finish does not form a “shell” on the surface of the metal like varnishes or paints. Instead the oil soaks into the pores of the metal, leaving a satin surface that emphasizes the grain and natural beauty of the metal. The linseed oil continues to harden over time and enhances the metal’s resistance to scratching and rusting. If rusting or scratching does occur, the metal can be easily repaired by sanding and reapplying linseed oil. Reapplication of linseed oil over time will improve the richness of the metal finish and provide additional protection for the future.