Stearin Candle Stock by Lime Saponification

Stearin candles burn harder and cleaner than tallow because the soft oleic part and the glycerin are taken out of the fat. In the 1850s the works did it with lime: tallow steamed with a cream of slaked lime becomes a lime soap, and washing it carries the glycerin away as a sweet water. Sulfuric acid then takes the lime back out, leaving the fatty acids, which are left to granulate and pressed to squeeze out the liquid oleic acid. Muspratt's Chemistry (1860) describes the whole process.