The distillation process was carried out in August when the oil content was at its height, and the fields were harvested by locals who collected the flowers into loose bundles of about one hundredweight, called ‘mats’ (nowadays most crops are harvested mechanically). At the peak of production in the Mitcham area there were at least six growers supplying the London pharmacists and markets, especially around the area of Buckersbury. Bunches of lavender were also commonly hawked in the London streets – as early as 1805 the text under a print of a lavender seller read:
‘Sixteen bunches a penny, sweet lavender’ is the cry that invites in the streets the purchases of this cheap and elegant perfume. The distillers of lavender are supplied wholesale and a considerable quantity is sold in the streets to the middling classes of inhabitants who are fond of placing lavender among the linen yet unwilling to pay for the increased pungency of distillation.
The earliest forms of extraction were carried out by the process of water distillation. As explained in Chapter 1, the flower heads (not the stalks; using the heads only ensured a top-quality oil) were immersed in a container of water which was then heated. After about half an hour’s heating, when the distillate had began to emerge, the fire was dampened down. The aromatic oil was then carried over in a condenser with the water vapour into a copper container, where the distillate separated out into two layers with the volatile oil on top. At the end of six hours the distillation process was complete and the remains of the herb could be cleared away. The Mitcham stills were the largest in Britain and were bigger than the French field stills, with a capacity of between 700 and 1000 gallons. An 1874 survey states that 70 pounds of flowers would yield about one pound of oil – but this appears a very optimistic average!
Although the water distillation technique is still occasionally used in southern France, it was largely supplanted by the more efficient technique of dry steam-distillation at the beginning of the 20th century. In 1906, when this method was introduced, an acre of ground growing about 3,500 plants of English lavender could yield around 15 pounds of pure oil.
By the 1920s the lavender fields had all but disappeared from Mitcham, swamped by suburban development. During the 1930s the centre of lavender growing moved from Surrey to northern Norfolk and centred around the small town of Heacham. Although Norfolk still boasts a high quality essential oil, lavender growing has never again attained the importance it enjoyed in its hey day. Norfolk Lavender still cultivate 100 acres with several varieties of lavender for the production of essential oil and dried flowers, but today the bulk of lavender essential oil used in Britain is imported for use in traditional toiletries, air fresheners and perfumes as well as for detergents, waxes and other ‘industrial fragrances’. The highest quality lavender oil, with an ester content of 50 per cent or more, is reserved for exclusive perfumes; lavender oil, with an ester content of around 40 per cent is employed in lavender water and colognes; while the lower grades (approximately 30 per cent esters) are used in soap, detergents, and the like.