Natural dyes usually give lower colourfastness than synthetic dyes, with washing fastness typically around grade 3 to 4 on the five-point scale used in the ISO 105 tests, and light fastness that varies widely by dye and mordant. Indigo is the special case, since it sits on the surface of the fibre and is prone to crocking, meaning colour rubs off on contact, particularly when new. None of this makes natural-dyed textiles unfit for sale, but it does mean you should set expectations with your customers and write care labels accordingly.
The tests buyers usually ask for are ISO 105 C06 for washing, ISO 105 X12 for rubbing, wet and dry, and ISO 105 B02 for light. Results are given as grades from 1 to 5, where 5 means no change. A synthetic reactive dye on cotton will often reach 4 to 5 in washing, while a well-made natural dye reaches 3 to 4 and sometimes less for certain colours.
What to expect by colour
- Indigo blue: good light fastness, but dry and wet rubbing are often low, and loose indigo transfers to lighter cloth, hands and furniture until it has been washed a few times.
- Madder and other reds: washing fastness usually fair to good when properly mordanted, with moderate light fastness.
- Pomegranate and other yellows: tend to have the lowest light fastness among common natural dyes and may fade noticeably in a sunny shop window.
- Iron black and brown: reasonable fastness, but iron can weaken cotton over time if the dye is not well rinsed.
- Overdyed greens and purples: fade unevenly because the two component dyes have different fastness, so the shade shifts as well as lightens.
Setting expectations and care labels
Tell customers in product copy that the colour is natural and will soften with washing, and treat that as part of the appeal rather than a defect. Care labels should say cool wash, separately for the first few washes, mild detergent, no bleach, dry in shade and iron on the reverse. For indigo, add a note about transfer onto light surfaces when new.
Ask the maker for a pre-washed finish if your customers expect to use the product straight away. Pre-washing removes loose dye and reduces crocking, and the cost is small compared with returns. Cushion covers and table linen benefit most, since they rub against sofas and plates.
Testing before you commit
Send sealed samples from the approved pre-production lot to an accredited laboratory for washing, rubbing and light tests, and compare the results with what you need for the product's use. A scarf can live with grade 3 rubbing, a white sofa cannot. If a supplier claims synthetic-level fastness from natural dyes, treat it as a reason to test rather than a reassurance, since substitution of synthetic dye for natural is one of the common problems in this trade.
How we handle this
We send sealed samples to an NABL-accredited laboratory for dye fastness so you have numbers rather than assurances, and we check during visits that the dye process matches what was quoted. Before packing we inspect for loose dye and transfer. If you are deciding between natural and synthetic dye for a range, a free 20-minute sourcing review will help you weigh the trade-offs.