A lab dip is a small piece of your fabric dyed to match your colour standard. It is the first link in a chain that should end with every carton in the order sitting inside an agreed range of that colour. Colour goes wrong in predictable places: a vague standard, judging under the wrong light, approving one swatch when bulk arrives in several dye lots, and reorders matched to the last batch instead of the original. Each has a known fix, and this guide sets them out in the order they arise.
On orders placed through Garments Hub BD, sampling runs in a fixed order: proto, fit, lab dip, then the pre-production (PP) sample. Bulk starts only after you approve the PP sample in writing. Colour approval therefore sits early in the timeline, and every extra round of comments adds days before the PP sample can be made.
Setting the colour standard
The dye house matches to something physical. The clearest standard is a swatch of fabric in the target colour, ideally on a similar fibre and weave, cut into two pieces so that you and the dye house hold identical copies. A reference from a printed colour book also works, provided both sides hold the same edition on the same material, since paper and textile versions of one reference differ.
Expect limits when the standard and the fabric differ. A colour matched on cotton jersey will never look quite the same on polyester tape or a nylon zip, because each fibre takes dye differently. Approve body fabric, rib, thread and trims as separate dips against the one standard, and accept that they will be close rather than identical.
Lab dip rounds and options
For each colour the dye house usually submits two or three options per round, marked A, B and C, dyed on the bulk fabric quality. You approve one, or reject all of them with a comment that tells the colourist which way to move. Vague comments such as "not quite right" cost a round; directional comments save one. Sign and date the approved option, keep half, and return half. The plain directions a colourist can act on are these:
- Lighter or darker
- Redder or greener
- Yellower or bluer
- Brighter or duller
Light sources and metamerism
Metamerism is when two colours match under one light and part under another. It happens because different dye recipes reflect light differently across the spectrum, and it is common when a standard and a fabric are of different fibres. The remedy is to judge in a light booth under more than one source: daylight (D65) first, then the fluorescent light used in your stores, then incandescent light (illuminant A). Name the primary and secondary light in your colour brief.
Most dye houses also measure dips with a spectrophotometer and report the difference from the standard as a Delta E value. A pass limit of about 1.0 under the CMC 2:1 formula is common in the trade. The instrument reading supports the decision; the final judgement is still made by eye in the booth.
Approving a shade band for bulk
Bulk fabric is dyed in batches, and no two dye lots are identical. Approving a single swatch leaves no rule for the lots that come out slightly lighter or darker. A shade band solves this: swatches from the bulk lots, arranged around the standard, showing the range you accept. Lots outside the band are corrected or re-dyed before cutting.
Within a garment, shade must hold across panels. Each garment is cut from one lot, and cut panels are numbered and bundled so that a sleeve never meets a body from another roll. Rolls are marked by lot, and a carton should hold one lot of a colour, so a shop shelf does not show two shades side by side.
Strike offs for prints and yarn dyed fabric
A print is approved through a strike off: the artwork printed on the actual bulk fabric, in the real colours, by the method planned for bulk. It is judged for colour, placement, scale and hand before the print run starts. For yarn dyed stripes and checks, the dyed yarns are approved first, then a short length of the woven or knitted pattern, because colours read differently once they sit next to each other.
Keeping the shade on reorders
Reorders drift when each new lot is matched to the last bulk rather than the original. Keep the approved standard sealed in an envelope, away from light, which fades it. Ask the dye house to record the recipe of the approved bulk lot. Match every reorder to the original standard, and ask for a fresh lab dip whenever the mill, the yarn or the fabric quality changes.
Four fastness tests and the grades to require
Fastness is how well a colour stays in the fabric in use. Washing (ISO 105-C06), rubbing (ISO 105-X12) and perspiration (ISO 105-E04) are graded 1 to 5 on the grey scales, where 5 is the highest grade. Light (ISO 105-B02) is graded 1 to 8 against the blue wool references, where 8 is the highest. US buyers may name AATCC 61 for washing and AATCC 8 for rubbing. Grades buyers commonly require, as a starting point:
- Washing: grade 4 for colour change and 3-4 for staining onto adjacent fabric.
- Rubbing: grade 4 dry and 3 wet, with 2-3 wet often accepted on very dark shades and indigo.
- Perspiration: grade 3-4 for colour change and staining, which matters most on sportswear and underwear.
- Light: grade 4 is a common minimum for everyday clothing; garments worn mostly outdoors usually need more.
What to put in your colour specification
- Colour standardA physical swatch or a named colour book reference, with two identical copies, one held by you and one by the dye house.
- Light sourcesThe primary and secondary light for judging, for example D65 daylight and the fluorescent light in your stores.
- ToleranceA visual match in the light booth, with an instrument limit such as Delta E 1.0 under CMC 2:1.
- Parts to matchBody fabric, rib, thread, zips and tapes listed, each to be approved as its own dip.
- Shade bandApproval of the bulk lot range before cutting, one lot per garment and one lot per carton.
- Fastness gradesWashing, rubbing, perspiration and light, each with its ISO method and the minimum grade you accept.
- Reorder ruleMatch to the retained original standard and the recorded recipe; a new lab dip when the fabric changes.
Questions buyers ask
How many lab dip rounds should I expect?
Usually one or two for a standard colour on cotton. Bright, very dark or fluorescent shades, and standards on a different fibre from the fabric, often take more. Each round adds days before the PP sample, so send a clear physical standard, name your light sources and give directional comments on every rejected option.
Can the rib and trims match the body colour exactly?
Close, but rarely identical. Rib, thread, polyester tape and a nylon zip each take dye differently from a cotton body, and they can match under daylight yet part under store light. Approve each part as its own dip against the same standard, and judge them together in the light booth before signing.
Why does my approved colour look different in the shop?
Usually because of metamerism: the colour was approved under daylight and the shop uses a different light. Two dye recipes that match in one light can part in another. Judge dips under the store light as well as daylight, and name that light in your colour brief before the first round.
Do I need all four fastness tests on every colour?
Not always on every colour. Test washing and rubbing on the darkest and brightest shades, which are most likely to fail, and perspiration on garments worn close to the skin during activity. Pale shades are usually more at risk on light fastness, so include them in that test.
Will a reorder match the first order?
It should fall within your shade band if the dye house matches it to the retained original standard, uses the recorded recipe and dyes the same fabric quality. A change of mill, yarn or fabric means a fresh lab dip, approved against the original standard rather than the last bulk lot.
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