I boil the soybean oil myself. I just pour a whole bottle into a large pot, open the doors and windows, make sure the fire extinguisher is handy just in case, and heat it till it smokes. I got the idea partly from seasoning cast iron pots; if you lay the oil on heavy, and bake at 400 deg for an hour, the pot comes out with a coat of varnish. Then I learned that most of the printing ink in use today is soy based as well. Soybean polymerizes when heated, just like linseed. Other non-spoiling oils like walnut and olive work, as does animal fat, but they don't dry to a varnish. Soybean will go rancid if exposed to air for long periods, but the fact that the boiled stuff dries, keeps that from being a problem. Incidently, I set it with a heat gun after I rub it in, just like I do linseed, otherwise, theres a lot of hand rubbing involved to generate the heat needed to set it. One day I'll try it with a setting agent and see how that works. I currently use a paste of boiled soybean and beeswax as a periodic top coat for just about everything, wood, leather, steel etc.
