Shade matching means checking that a dye lot gives the same colour as your standard. The check uses a spectrophotometer, a light box and an agreed tolerance.
How close it should be depends on your product. A dye for a fashion fabric that is matched by a mill needs a tight tolerance. A dye for paper or low-cost goods may accept a wider one. What matters is that you agree the number and the method in writing.
Shade matching applies at two levels. The dye maker matches each dye lot to its standard. Your mill then matches each dyed batch to your customer's colour. A small drift at the first level becomes extra corrections, re-dyes and delays at the second.
How shade is measured
The lab dyes a standard and the lot side by side on the same substrate and under the same conditions. A reflectance spectrophotometer measures both. Software reports the difference in lightness, chroma and hue, and a single colour difference value, written ΔE.
The CMC formula, used in ISO 105-J03, weights these differences closer to how the eye sees them. For textiles it is usually used with a 2:1 ratio of lightness to chroma, written ΔE CMC(2:1).
Setting the tolerance
- Agree a total colour difference limit, such as ΔE CMC(2:1) of 1.0 or less, which is a common commercial pass level for many textile uses.
- Add direction limits if needed, for example no lot redder than the standard by more than a set amount.
- Agree the light sources for checking, usually daylight D65 plus one or two others such as TL84 or incandescent A.
- Agree the substrate, depth of shade and dyeing method used for the test.
- Agree that a visual check in a calibrated light box confirms the instrument result.
Metamerism and strength
Two samples can match under daylight and differ under shop lighting. This is metamerism. It is common when a supplier changes the shading components in a blended dye. Checking under more than one light source catches it.
Shade and strength are linked. A weak lot can look lighter, and the software may report it as a shade difference. Measure dye strength first, then correct for strength when judging shade.
When a lot fails
Agree in advance what happens. Options include rejecting the lot, accepting it with an adjustment, or having the supplier re-standardise it before shipping. Keep sealed samples from every shipped lot so you can recheck later, and record the measured values so trends show up over time. For a wider view, read how to check batch-to-batch consistency in dyes.
Next step
We hold your standard, compare each lot before loading and have independent tests done when needed. To set this up, book a free sourcing review.