Expression
Expression as a method of fragrance extraction where raw materials are pressed, squeezed or compressed and the oils are collected. In contemporary times, the only fragrant oils obtained using this method are the peels of fruits in the citrus family. This is due to the large quantity of oil is present in the peels of these fruits as to make this extraction method economically feasible. Citrus peel oils are expressed mechanically, or cold-pressed. Due to the large quantities of oil in citrus peel and the relatively low cost to grow and harvest the raw materials, citrus-fruit oils are cheaper than most other essential oils. Lemon or sweet orange oils that are obtained as by-products of the commercial citrus industry are among the cheapest citrus oils.
Expression was mainly used prior to the discovery of distillation, and this is still the case in cultures such as Egypt. Traditional Egyptian practice involves pressing the plant material, then burying it in unglazed ceramic vessels in the desert for a period of months to drive out water. The water has a smaller molecular size, so it diffuses through the ceramic vessels, while the larger essential oils do not. The lotus oil in Tutankhamen's tomb, which retained its scent after 3000 years sealed in alabaster vessels, was pressed in this manner.
Read more about this topic: Fragrance Extraction
Famous quotes containing the word expression:
“But the wise know that foolish legislation is a rope of sand, which perishes in the twisting; that the State must follow, and not lead the character and progress of the citizen; the strongest usurper is quickly got rid of; and they only who build on Ideas, build for eternity; and that the form of government which prevails, is the expression of what cultivation exists in the population which permits it.”
—Ralph Waldo Emerson (1803–1882)
“The novel is the highest form of human expression so far attained. Why? Because it is so incapable of the absolute.”
—D.H. (David Herbert)
“The psychological umbilical cord is more difficult to cut than the real one. We experience our children as extensions of ourselves, and we feel as though their behavior is an expression of something within us...instead of an expression of something in them. We see in our children our own reflection, and when we don’t like what we see, we feel angry at the reflection.”
—Elaine Heffner (20th century)