One of the most popular scents for perfume is the scent of real roses. Traditionally it is believed that Arab chemists were the first to find a way to produce useable perfume oils from roses. Rose oil commands a very high price, because it is so laborious to extract. The harvesting of the buds is done by hand before sunrise and the petals are used to create oil and scent extracts the very same day. It takes many pounds of rose petals to make just one ounce of oil. So how is the rose scent used in perfume created?
There are three current methods of getting oil out of the rose petals.
In the solvent extraction method the rose petals are mixed in a vat or tub with some kind of solvent like hexane. The hexane draws out the rose aroma, as well as some wax and pigments. A vacuum process removes the Hexane and leaves a thick wax-like mass which is called Concrete in the perfume industry. Alcohol is put through the Concrete which draws out the scent part only. This alcohol mixture is then evaporated under low pressure, leaving the pure scent extract behind. This is called Rose Absolute and is an amber yellow to deep red in color. This is the least expensive method of scent extraction.
- Extraction by a solvent
- Extraction by steam distilling
- Extraction via superficial carbon dioxide
Removing rose scents by steam distilling involves large stills filled with rose petals and water. The still is heated for a period of time, until the water vapor along with rose oil vaporizes out of the still and into a condenser, where the condensate is run off into a container. Then the water is drained off from the oil leaving very concentrated oil. The drained off water is then re-distilled to extract water soluble oils or alcohols that still exist in the water. There is also a method to perform a combination distillation-extraction of this left over water. These water soluble constituents are mixed with the original concentrated oil to get the final oil product called Rose Otto or Attar. Rose Otto is made up of around 20% of the concentrated oil and 80% of the water soluble products. It is then diluted heavily when used in perfume. It is pale yellow to olive green in color and will crystallize at room temperature. Bulgaria is the largest producer of Rose Otto.
The carbon dioxide extraction method is the most expensive method of the three and the price of your perfume may reflect that. Carbon dioxide, which is normally a gas at normal pressures, is put under pressure until it liquefies. The Rose petals are mixed with liquid carbon dioxide and heated at very low temperatures. The rest of the process is similar to the standard solvent extraction method. When normal pressure is restored to the carbon dioxide it turns back into gas and leaves the aroma extracts behind. The CO2 does not leave any odor of its own behind.
A good deal of quality control must follow the process of making and buying pure rose oils as it is not unusual for it to be unscrupulously diluted with essential oils from the Geranium flower or Palmarosa herb (related to the Geranium), or even other alcohol related chemicals.