The iris

Iris pallida, Iris alba, Iridaceae

The myth
Iris, messenger of the gods spread her multicolored scarf, thus creating a bridge made of a rainbow, linking the earth and the beyond, guiding the souls of women to their final resting places.

The story
Iris means rainbow in Greek.
The Egyptians were the first to use rhizomes, the underground stem of perennial plants, to extract fragrant smoke. They are at the origin of the first potpourri. The philosopher Theophrastus, 300 BC. JC, already knew the recipe to extract the secret perfume from the rhizomes.
The iris is the initial model of the fleur-de-lis. Clovis had made it his emblem when, with his horses and his army, he was able to cross a ford on which this plant grew in abundance and made him win the battle. Later, to get closer to the Church, the white lily, emblem of chastity, replaced the iris.

A bit of botany
Ornamental plant, there are more than 200 horticultural varieties. The iris is a genus of perennial plants with rhizomes or bubbles, of the family Iridaceae. Its sophisticated flowers are composed of six pieces including three real petals. They can reach a height of 70cm in certain varieties such as the iris Pallida, or the Alba and only reach 20cm in the dwarf iris. Its unevenly shaped, swollen, gnarled rhizomes are covered with a thin brown bark, they hold the flower to the ground, and themselves have roots.

The perfumer's iris
Not all irises have the same olfactory qualities. These are the pale mauve iris pallida and the Florentina, the Alba, which are used for their fragrant rhizomes. These hold the irone (chemical principle to which the iris owes its smell) sought after by perfumers, a fragrance close to that of the violet. These irones are the aromatic molecules specific to the iris.
From the highest antiquity, the secret of extraction to obtain the perfume of the iris was already known. A first step consists in pulling out rhizomes of the iris pallida that have remained in the ground for more than 3 years only. Once these have been carefully peeled (unshelled we obtain a darker essential oil which we will call black iris but the peeled rhizome gives better quality extracts), they are then cut into strips and then left to dry in the sun for two weeks. They are then stored in bags for three years to allow the “irone” molecule to reveal itself to the maximum. The rhizomes acquire after this long desiccation a perfume of violet. They are then crushed and reduced to powder.

Its mode of extraction
Once the irone concentration has been obtained, the rhizomes are ground and then turbodistilled.(link) This is when the iris butter is extracted, which is in fact only the essential oil which has solidified and one calls butter only for the iris. This iris butter contains 15% irone. It is then subjected to a new fractional distillation (link) which makes it possible to increase the irone concentration of the final product (up to 60%) and which is called the absolute.

In perfumery
Three tons of fresh rhizomes will give one ton of dry rhizomes, 500 kg of dry rhizomes give 1 kg of iris butter and 4 kg of iris butter give 1 kg of absolute. This long process of cultivation, maturation, and the multiplicity of extraction operations make iris absolute one of the most expensive materials in the perfumer's palette. Even if it is the rhizomes from which the absolute is drawn, it is definitely a heart note. Its fragrance is described as halfway between flower and wood. The iris is one of the noblest materials in perfumery.

Based on research by Tachka Sofer
Bibliography
The mythology of plants A.Gubernatis ed. Horticultural SocietyL'ethnobotanique Méditerranée, by P.Lieutaghi, ed. Acte sudNatural and cultural history of perfume plants by Fr. Aubaille-Sallenave, ed. Ibis pressThe essential oils of G.Roullier, ed. DanglesThe perfumes of E. de Feydaux, ed. R. Laffont