Dye Lot Control and Colour Matching Across Repeat Orders

The second order is where colour goes wrong. The first order had a lab dip, several rounds of comments and a lot of attention. The second order is placed by email with a reference to the previous colour name, and it arrives two shades off. For a bra sold as part of a matching set, a shade difference between the bra and the legging is unsellable. Colour control is a documentation process, and it has to be designed before the repeat, not after it.

Why Repeat Orders Drift

Shade varies for reasons that have nothing to do with carelessness. Dye stuff batch, water quality, dyeing temperature profile, fabric construction from a different knitting machine, and the finishing route all shift the result. Even with the same recipe on the same machine, a lot dyed six months later will not be identical. The realistic goal is controlled tolerance, not exact reproduction.

Lab Dip and Shade Approval Protocol

Require lab dips on the actual production fabric construction, not on a substitute. Request at least three dips: one on shade, one slightly lighter and one slightly darker, so you can see the direction of the recipe rather than approving a single point.

Approve under standardised lighting. D65 is the primary illuminant for apparel, but also check under a store-typical source such as TL84 or a warm incandescent source to catch metamerism, where two samples match under one light and separate under another. Keep a signed and dated approval swatch, cut into at least three pieces: one for you, one for the factory, one for the mill.

Specifying Tolerance Numerically

Agree how close is close enough before production, in numbers. Commercial practice for apparel is commonly a Delta E of 1.0 or less against the approved standard, measured in CIE Lab space, and 0.8 or tighter for components within a matching set. Confirm the measuring instrument settings, including aperture size and whether specular component is included, since those affect the reading.

Pair the numeric tolerance with a visual reference: colour change assessed against the ISO 105-A02 grey scale, with a rating of 4 to 4-5 as the usual acceptance level for production variation.

Dye Lot Numbering and Traceability

Require a unique dye lot number on every fabric roll, and a cutting record that maps each carton to the lot numbers it contains. If a complaint arrives eight months later, that record is the only way to know whether it was one bad lot or a systemic shift.

Cutting Rules That Hide Small Differences

Small within-lot variation is normal and manageable if you cut sensibly. Keep one dye lot per garment: never mix panels from two lots in a single bra. Sequence the cutting table so panels for one garment come from adjacent sections of the same roll. For matching sets, cut the bra and the legging from the same lot, and if volume requires more than one lot, ship by lot rather than mixing across a customer order.

Handling an Off-Shade Lot

Decide the remedy in advance. Options include accepting at a discount for a channel where it will not be compared side by side, re-dyeing if the fabric and schedule allow, or rejecting and re-knitting. Rejection is expensive and should be the documented consequence of exceeding a tolerance that both parties signed. Without a signed numeric tolerance, an off-shade discussion becomes an argument about opinion, and the buyer usually loses it.