Lab Dips and Colour Approval: How Knitwear Buyers Sign Off on Colour

By YZR Sweaters · 2026-09

Colour approval is where a buyer's reference becomes a factory's instruction. Done well, it is quick and cheap: a few small dye samples, judged under the right light, signed off with a written tolerance. Done as a formality, it becomes a dispute.

What are lab dip, strike-off and bulk lot?

Colour approval runs on three different samples, and buyers who treat them as one thing are the ones surprised by bulk.

Lab dip (laboratory dip)

A lab dip is a small sample of yarn or knitted fabric that a dyehouse colours to your target shade before any bulk material is dyed. The mill proposes a recipe, the buyer confirms or corrects it, and the approved dip becomes the physical colour standard for the order — on sweaters, a knitted swatch judged on the structure it will be sold in.

Strike-off

A strike-off is the equivalent sample for a printed or colour-woven design: a small trial piece confirming pattern layout and colour registration. A plain solid knit does not need one; a printed logo, engineered stripe or jacquard does.

Bulk lot (production lot)

A bulk lot is the quantity actually dyed for your order. Each separate dyeing run produces its own dye lot, and two lots dyed from the same recipe still differ slightly. That lot-to-lot variation is why sweaters in one shipment may not quite match each other.

Why is bulk colour never identical to the lab dip?

• Yarn batch — fibre from a different production batch absorbs dye at a slightly different rate.
• Vessel size — a full dyeing machine differs from a laboratory beaker in liquor ratio, movement and heating.
• Water and dyeing curve — mineral content in the water and differences in temperature and time shift how much dye fixes to the fibre.
• Fibre blend — each component takes dye at its own rate, so a change in blend proportion reads as a colour shift.

So “identical to the approved dip” is not a clause a mill can honour; the workable wording is “within the agreed tolerance of the approved standard”.

How should you judge a colour sample?

• Use a standard light source. Assess in a daylight-balanced viewing booth or genuine north-facing daylight. Office fluorescent and warm shop bulbs pull a shade differently.
• Judge physical samples side by side. Place dip and reference touching under the same light. Comparing one today and the other tomorrow asks memory to do a job it cannot do.
• Never approve from a screen. A phone or monitor adds its own rendering; photographs share progress but are not evidence of a match.
• Watch for metamerism. Metamerism is when two samples appear to match under one light and look different under another — common when dip and bulk use different dye chemistry. Check under at least two sources, including the light your customer shops in.

How many approval rounds are normal?

One or two rounds is the usual rhythm for a commercial solid: submit, comment, correct, approve. Difficult targets — pale pastels, clean whites, true reds, deep navy — often need a third or fourth round; the margin for a visible shift is tiny. Each round costs days at the front of the calendar, before yarn purchase and knitting.

What should you write when you approve a colour?

• The reference and approved dip, identified by sample number, date and colourway.
• The light source used for approval, so no one re-litigates the match later.
• The bulk tolerance — a measured colour-difference value or a visual grey-scale rating, with the method and scale confirmed by your testing laboratory.
• Whether lot-to-lot variation is allowed inside that tolerance, or all lots must sit within one shade band.
• What happens if bulk falls outside tolerance — re-dye, replacement, or acceptance with a price adjustment.
• Who retains the standard: both sides hold a signed physical dip, for bulk comparison and incoming inspection.

How do you reduce dye-lot risk in production?

• Dye the whole order in as few lots as possible — one lot per colour removes internal variation.
• Keep one colour on one yarn batch rather than spreading it across several.
• Where an order needs several lots, keep them inside a shade band and dye the later lots against the retained standard.
• Record the recipe with the lot so repeats can be matched; the dyeing route itself affects repeatability — see yarn-dyed versus piece-dyed knitwear.

Which approval mistakes cause most colour claims?

• Approving after one glance, or from a photograph.
• Judging under whatever light was in the room.
• Approving without a stated tolerance, then rejecting bulk against an unwritten expectation.
• Changing yarn lot after approval without a fresh dip.
• Confusing shade with fastness: a matching dip says nothing about the wash — see our sweater colour fastness guide.

How YZR Sweaters runs colour approval

At YZR Sweaters, a Dongguan knitwear manufacturer, colour approval is a scheduled step, not an afterthought. Dips are submitted on the actual yarn and knit structure for OEM/ODM programs — original equipment manufacturing and original design manufacturing — and the approved standard is retained by both sides so bulk and repeats are judged against the same physical reference, within the MOQ (minimum order quantity) the buyer has booked. Our partner factories hold BSCI, SEDEX and Oeko-Tex certification, welcome customer audits, and support full inspection and third-party inspection (SGS / BV). Our guide to sweater colour trends and Pantone references covers how a palette is built before the first dip is cut.

Frequently asked questions