Lightfastness and Caring for Naturally Dyed Items

One honest limitation of natural dyes is that many are less lightfast than modern synthetic dyes — meaning they fade more readily when exposed to light over time. This is not universal (some natural dyes are remarkably stable), but it is worth understanding so you can make informed choices and properly care for the things you make.

What Is Lightfastness?

Lightfastness refers to a dye’s resistance to fading when exposed to light, particularly UV radiation from the sun. It is measured on a standard scale (the Blue Wool Scale in the UK, the AATCC scale in the US) from 1 (fades very rapidly) to 8 (extremely stable). Many synthetic dyes used in commercial textiles rate 5–8. Natural dyes vary widely: from very fugitive (1–2) to quite good (5–6).

The Best and Worst for Lightfastness

Among the most lightfast natural dyes are weld (luteolin dyes), madder (on wool with alum, in the 4–5 range), and indigo (particularly stable in its reduced, fibre-bound form — often rated 6 or higher). Cochineal on alum-mordanted wool is rated around 4–5, which is respectable.

Among the least lightfast are anthocyanin-based dyes — the purples and pinks from purple cabbage, elderberries, and many flowers. These can fade noticeably within weeks of sunlight exposure. Black walnut, despite producing strong initial colour, also fades over time toward brown. Iron modifiers generally improve lightfastness.

Improving Fastness

Using the right mordant helps significantly. Alum is the standard choice for good fastness. Iron afterbaths improve fastness in many cases. Wetting-fastness (resistance to fading during washing) is generally better than lightfastness for most natural dyes — colours that fade in sun may survive washing well.

Washing Naturally Dyed Textiles

Hand washing in cool to lukewarm water with a gentle, pH-neutral soap (no bleach, no enzyme-based detergents which can break down protein fibres) is ideal. Avoid soaking for long periods. Do not tumble dry or wring. Dry flat or hang in the shade, never in direct sun. Even naturally dyed items that are not particularly light-sensitive benefit from shade drying, since prolonged UV exposure during drying can degrade both colour and fibre.

Storing Naturally Dyed Items

Store away from direct light — inside a drawer, in a fabric bag, or wrapped in acid-free tissue. For woven or knitted pieces, folding is better than hanging (which can distort the shape over time). Cedar blocks or lavender sachets are preferable to mothballs for protecting wool items. A naturally dyed item properly cared for can remain beautiful for decades; some historic naturally dyed textiles have survived centuries.