KEEPING LIFE COLOURFUL: TEMPERATURE AND HUMIDITY
Temperature and humidity can both contribute to colour degradation.
Excessive dryness causes damage, especially to the dye sites of elastic fibers, such as wool, which rely on a certain amount of moisture to maintain their integrity. Temperature and humidity should be kept as constant as possible; changes in either of these may cause fibers to expand and contract, which, over time, can also cause damage and deterioration of colours. Excessive moisture can supply an environment wherein unwanted chemical reactions can occur more easily.
Ideally, temperature should be kept around 70 degrees Fahrenheit though some slight fluctuation in either direction is permissible, as long as it occurs gradually. For instance, temperature may be slightly lower in winter to save energy costs, but any change should be affected slowly, over a day or so, so as not to place the fabrics and hence the colours under undue stress.
As for humidity, a relative humidity of 30% - 50% is best, though some small fluctuation is allowable as long as it occurs gradually.
In areas where climate control is unavailable (such as in historic buildings), you can still moderate the temperature and relative humidity through the use of fans, humidifiers and dehumidifiers, and portable heating or cooling units.
Air flow is also a concern for colour preservation.. Proper circulation, combined with the suggested humidity, will help to prevent the growth of mould and mildew, which may stain or weaken delicate or antique textiles.