If you crush a leaf in your hand and bring it to your nose, the scent you receive is the shortest answer to this question. In the leaves, in the bark, in the flowers and in the heartwood, a plant keeps a very small amount of fragrant compounds, held in tiny sacs or glands. Essential oil is that part, taken out and gathered together.
The plant does not make these compounds to serve our noses. They are how the plant lives: to call bees and butterflies for pollination, to keep insects away, to seal a wound in the bark. We find this well worth remembering each time we open a bottle of essential oil, because it reminds us that we are holding a part of a tree's work.
Why each drop needs so much material
The amount of fragrant compound in a plant is usually very small compared with its mass, and that ratio differs greatly from one species to another. Some give oil quite easily, such as citrus peel or mint leaves. Some need tens of kilos of material for a tiny amount, and flowers are usually the costliest group, because they have to be picked at the right hour and stay fresh only a few hours.
The moment of harvest changes the result too. From the same garden, picking at dawn and picking at midday give two different yields. The same species grown in one region and another gives a different scent, because soil, altitude, rainfall and sun all leave their mark on the plant. This is why a real material always has a season, and every season differs a little from the one before.
The two most familiar ways to take essential oil
The most common way is steam distillation. The material is packed into a still, hot steam passes through and carries the fragrant compounds along with it, and then that vapour mixture is cooled. Water and oil separate into two layers, and the oil layer on top is taken. The remaining water carries scent too, and in many places it is kept and used as a gentle scented water.
With the peel of the citrus family, cold pressing is usual. The oil sacs sit right in the outer peel, so pressing those sacs open is enough for the oil to run out, with no heat needed. This way keeps the freshness of just-peeled rind, and that is why citrus in a bottle of perfume sounds so alive.
There is one very old way, rare today, of spreading flowers on a layer of fat so the fat draws in the scent gradually, repeated many times with fresh flowers. People in Grasse in France once did this with blooms too delicate for heat. We tell this detail because it shows how patient the fragrance craft was before machinery.
A bottle of essential oil in your home
Essential oils composed by ZUNGZA come in a 15 ml glass bottle, and each time you use it you need very little. A few drops in a bowl of warm water beside the desk. One drop on a small piece of wood in the towel drawer. A few drops in a mist diffuser about twenty minutes before sleep, then switched off.
Sunlight and heat are the two things that change essential oil fastest, so keep the bottle standing somewhere cool, tightly capped, out of direct sun. The shelf life is three years from the date of production, and a bottle kept properly still holds its character right to the end.
A few questions you often send us
What is the difference between essential oil and fragrance compounds
Essential oil is taken out of a plant, while synthetic fragrance compounds are created in a laboratory. Both have their place, and we regard each according to the work it does.
Why does the same essential oil smell different from batch to batch
Because the plant changes with the season, with the soil and with the weather. Small differences between batches are the sign of a real material.
How do I keep a bottle of essential oil for a long time
Keep it somewhere cool, tightly capped, out of direct sun and away from hot places such as the stove or beside a glass door. The shelf life is three years from the date of production.
Read more the three trees behind our forest scents, three familiar materials in scent, and how to keep candles, perfume and essential oils.