A lab dip is a small piece of your fabric dyed in the mill's laboratory to match a colour standard before any bulk dyeing starts. Approval usually takes 7 to 14 days from the day the mill receives your standard, and the mill typically sends three options per colour. Each round after the first adds roughly a week, so the number of rounds matters more than the speed of any single one.
The lab dip exists because dye recipes behave differently on every base cloth. A recipe that hits a navy on one cotton poplin will drift on another with a different yarn or finish. The mill needs your exact base and your exact standard before it can promise a match.
What the mill needs from you
- A physical colour standard: a swatch, a yarn or a reference from a colour system. A photograph or a screen value is not enough, because screens are not calibrated to dyed cloth.
- The base fabric you will actually buy, in RFD (ready for dyeing) form, so the dip is made on the right cloth.
- The light source you will assess under, normally daylight D65 with a secondary source such as store lighting.
- The tolerance you will accept, usually expressed as a Delta E value or simply as "commercial match".
- Any fastness requirements, because some shades can only be reached with dye classes that trade depth of colour for washing or light fastness.
How the approval round works
The mill's lab dyes three small pieces using slightly different recipes and labels them A, B and C. They are couriered to you with the recipe reference written on each ticket. You assess them against your standard in a light booth, under the agreed light source, and send back a written approval naming the option, or comments on which direction the colour should move.
Metamerism is the common trap. Two pieces can match under daylight and separate under shop lighting, so always check under at least two sources. If none of the three options is close, say what is wrong in plain words, such as too red, too dull or too light, rather than asking for "another round".
Keeping the timeline short
Send all colours for a season together, not one at a time, because the lab schedules work in batches. Approve by email with a photograph of the signed ticket, and keep the signed physical dip in a sealed envelope; it becomes the standard for bulk. Ask the mill to confirm the dye class and recipe number against the approved dip so the same recipe runs in bulk.
Allow time in the plan for a second round on difficult shades. Bright reds, deep blacks and pale greys usually take two rounds. If the deadline is fixed, approve the closest option and record the comments as an accepted deviation rather than wait for a perfect match.
Where we come in
We collect lab dips at the mill, check the ticket and recipe reference, and courier them with the signed standard so nothing is lost in transit. On bulk, we cut sealed samples from the first lot and send them to an NABL-accredited lab for shade and fastness testing against the approved dip. Weekly updates show you where each colour sits in the round.