The ''sfumatura'' or slow-folding process is a traditional technique for manually extracting the

essential oil An essential oil is a concentrated hydrophobic liquid containing volatile (easily evaporated at normal temperatures) chemical compounds from plants. Essential oils are also known as volatile oils, ethereal oils, aetheroleum, or simply as the o ...

s from

citrus ''Citrus'' is a genus of flowering plant, flowering trees and shrubs in the rue family, Rutaceae. Plants in the genus produce citrus fruits, including important crops such as Orange (fruit), oranges, Lemon, lemons, grapefruits, pomelos, and lim ...

peel using sponges. Dating back to 18th-century

Italy Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical re ...

, the process is still carried out in

Sicily (man) it, Siciliana (woman) , population_note = , population_blank1_title = , population_blank1 = , demographics_type1 = Ethnicity , demographics1_footnotes = , demographi ...

today, although it is increasingly rare. 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 Using a ''rastrello'', a special

spoon A spoon is a utensil consisting of a shallow bowl (also known as a head), oval or round, at the end of a handle. A type of cutlery (sometimes called flatware in the United States), especially as part of a place setting, it is used primarily for ...

-shaped

knife A knife ( : knives; from Old Norse 'knife, dirk') is a tool or weapon with a cutting edge or blade, usually attached to a handle or hilt. One of the earliest tools used by humanity, knives appeared at least 2.5 million years ago, as evidenced ...

, the fresh peel is de-pulped. It is then thoroughly washed with

limewater Limewater is the common name for a saturated aqueous solution of calcium hydroxide. Calcium hydroxide, Ca(OH)2, is sparsely soluble at room temperature in water (1.5 g/L at 25 °C). "Pure" (i.e. less than or fully saturated) limewater i ...

and drip-dried on woven mats or special baskets for 3 to 24 hours, depending on the

ripeness In United States law, ripeness refers to the readiness of a case for litigation; "a claim is not ripe for adjudication if it rests upon contingent future events that may not occur as anticipated, or indeed may not occur at all." For example, if a ...

of the fruit, the

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...

, and the

humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity depe ...

. These steps harden the peel, causing the oil to spurt from the oil glands more easily, and the lime helps neutralize the

acid In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a sequ ...

ity of the peel.Di Giacomo p.64, Di Giacomo and Di Giacomo pp.125-126 A series of natural sponges is fixed upon a

terracotta Terracotta, terra cotta, or terra-cotta (; ; ), in its material sense as an earthenware substrate, is a clay-based ceramic glaze, unglazed or glazed ceramic where the pottery firing, fired body is porous. In applied art, craft, construction, a ...

basin or ''concolina'' and held in place with a wooden bar laid across the rim. The dried peel is folded and pressed against the sponges several times in a circular motion, causing a mixture of essential oil and peel liquids to pass into the ''concolina''. After finishing with the peel, the sponges are squeezed to recover additional oil and liquids. Finally, the oil is

decanted Decantation is a process for the separation of mixtures of immiscible liquids or of a liquid and a solid mixture such as a suspension. The layer closer to the top of the container—the less dense of the two liquids, or the liquid from which t ...

away from the heavier watery phase, which contains detritus from breaking the peel.

References

*{{cite book, editor=Giovanni Dugo , editor2=Angelo Di Giacomo, year=2002, title=Citrus, location=London, publisher=Taylor & Francis, isbn=0-415-28491-0 *Angela Di Giacomo. "Development of the citrus industry: historical note". pp. 63–70. *Angela Di Giacomo and Giovanni Di Giacomo. "Essential oil production". pp. 114–147. Citrus Essential oils