In the 1820's a French chemist, Michel Eugène Chevreul, had published his researches into fatty acids. By mixing a strong alkali with vegetable or animal fats he discovered that the solution separated into liquid and solid components. This technique, known as saponification, was already used by soap makers, but nobody had employed it for candle manufacture. William Wilson's son, George, experimented with this process; by adding a further distillation using a vacuum or high pressure steam he improved Chevreuil's basic chemistry. Price's were now able to refine tallow and vegetable oils to produce a harder, pure white fat known as stearin. Candles made from this burned brightly without smoke or smell. The same chemistry could also be applied to a range of unsavoury raw materials that had previously been unusable – skin fat, bone fat, fish oil and industrial waste greases could all be rendered into hard white candles.