The sfumatura or slow-folding process is a traditional technique for manually extracting the essential oils from citrus peel using sponges. Dating back to 18th-century Italy, the process is still carried out in Sicily today, although it is increasingly rare.Di Giacomo p.63-64 Despite the modern array of sophisticated machines for extracting citrus oil, even the best machinery does not approach the quality of sfumatura-produced oil.Di Giacomo and Di Giacomo p.124
