I found my sds. It has linseed and a proprietary “modified” oil, my guess is it’s a “boiled” tung. The heat treatment is probably correct since linseed won’t dry very fast if not pre-heat treated and heat treated tung will dry much faster. I’m pretty sure when you see anything that’s a “modified” oil then it’s brought up to high temp in the absence of oxygen to catalyze the molecules to start linking, forming polymers that are not fully cured, basically creating a thickened oil that will oxidize and dry faster and leave behind more of film forming layer. Tru-oil and many others use Stoddard solvent, basically a distillate like mineral spirits, white spirits or paint thinner - just more refined so has less other distillates and nearly none of the lighter volatiles. Today’s low odor paint thinner is basically like stoddard solvent since it has less of the lighter volatiles that evaporate more easily creating more odors. Wood finishing products is an interesting part of chemical engineering (my background was more in other types of specialty chemicals). If you see alkyd in an oil based product, then it has synthetic resins similar to polyesters to mimic the natural oils. I’ve seen some guitars finished in tru-oil with many layers that look like a nicely spray lacquered buildup.
