Lavender Oil Distillation
The stills usually employed by growers are of simple construction, any fault in the distillate being subsequently rectified by fractional distillation. The stills are constructed of copper, and generally built to take a charge of about 5 cwt. of flowers at a time. It is important to avoid burning, and the practice is to provide the stills with two chambers, with a perforated false bottom between, the lower chamber being filled with water which should be as soft as possible. Distillation is conducted by boiling the water beneath the charge with steam brought from a boiler to a coil, the top of which must be at least 1 foot beneath the bottom of the charge chamber. The oilflow from the condenser must be watched for, and complete distillation of the charge usually takes about six hours from commencement of the flow.
The yield of the oil is apt to vary considerably from season to season, as the age of the bushes and the weather will affect both the quantity and quality of the product. The amount of sunlight in the weeks before distillation has a great influence: the best oil is obtained after a hot, droughty season, heavy rains detract from the yield.
An acre of Lavender in its prime would in a favourable year yield from 15 to 20 lb. of oil, but taking the whole of the area planted as described above, an average yield of 12 lb. to the area would be a fair estimate.
The distillate should be left for several months to become quite clear and transparent before it is offered for sale.
At Hitchin, it has been calculated that 60 lb. of good flowers will yield on the average 16 fluid ounces of oil.
Growers not doing their own distilling, but preparing the flowers dry for market, should spread the stalks out in the open, on trays or sieves, in a cool, shady position, out of the sun, so that they may dry slowly. The trays should be raised a few feet from the ground, to ensure a warm current of air, and the stems must not be allowed to touch, or the flowers will be spoilt by the moist heat engendered. They must be taken indoors before there is any risk of them getting damp either by dew or showers. When dry, they should be stored in a dry place and made up into bundles. The flowers may also be stripped from the stalks and dried by a moderate heat. They have a greyish-blue colour when dried.
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