The aim in drying herbs is to remove the water content only, thus changing them as little as possible.
The old way was to hung the bunches of the herbs upside down in the kitchen where there were constant changes of temperature and light. The herbs were of little value as a result. Herbs dried in the sunshine will lose colour and quality as the heat makes the volatile oils evaporate.
The first and most important rule is always to dry herbs in the dark. At the same time, ventilation and good circulation of air round the herbs should be also provided. The temperature for drying can vary according to the needs of individual herbs, but during the process the temperature should be as constant as possible. Any excess moisture should be well drained before the herbs are put on to trays made by stretching pieces of nylon new tautly over the frames of old wooden boxes with the bottoms knocked down, the net being held in place with staples.
Many herbs dry quickly and successfully in a cool oven, no higher than 38C (100F). Leave the oven door slightly open to allow the moisture to escape.
Herbs can be also dried on the net covered trays where a constant heat is supplied by a boiler. Stand the trays on four little pieces of wood to allow the air to circulate round them.
A warm dark room can be ideal for the slow drying of some herbs. Stand the herb trays on pieces of wood to leave space for air to circulate.
A dry, dark and airy garden shed can be used in the summer months for herbs which need to be dried slowly. Any windows should be blocked off to keep out the light and the trays can be covered with paper to keep off the dust and insects which my find their way into the shed.
The airing cupboard or heated closet is the most suitable place for drying all parts of the herb. Leave the door slightly open for the moisture to evaporate and the air can circulate.
Many of the more fragile parts of an herb will dry slowly and well between sheets of butcher paper (avoid newspaper because of the ink) placed under the bed or chest of drawers in an airy room.
Herbs should be stored in dark-coloured glass, screw-top jars immediately they are dry, otherwise they pick up moisture from the air. They should not be stored in tins unless they are first placed in a cotton bag because contact with the tin can damage the flavour and aroma of the herb. Dried herbs should not be stored for longer than a winter season, or at most nine months, as they lose their colour, scent and flavour of kept for too long.