Originally Posted by
geargnasher
MJ, what you're talking about is how soap and grease is made commercially. The grease cooks don't melt pre-made stearates into oil, they actually make the grease from scratch by taking base oil, heating it to about 200F or so, and adding a metal hydroxide (sodium, lithium, magnesium, calcium, aluminum, antimony, etc.) and stearic acid (a fatty acid refined from beef tallow). The metal base and the stearic acid react to form a metal stearate within the oil itself.. This requires precision measurements for complete reaction with no leftovers, but requires much less heat than melting in stearates. The water from the reaction must be boiled off, other additives put in, and the whole mess milled, but that's basically it. The "salts" or "stearates", once formed by the acid/base reaction, require much more heat to melt than the final product does. This is why you can take sodium hydroxide and stearic acid and make regular ol' lye soap on the stove at about the temperature water boils, but if you ever want to remelt it, you have to go over 450F.