Lab Dips Explained: How to Approve Color for Performance Knit Fabric

Short answer: A lab dip is a small-scale dyeing of your actual base fabric against a color standard, used to lock color before bulk production. Approve it only when you have fixed the base fabric, the illuminants used to judge it, the tolerance method, and the sealed standard. Lighting conditions cause more rejected color than dye recipes do.

Key Takeaways

• A lab dip has to be dyed on the same construction and weight as bulk, because the same recipe reads differently on a different base fabric.
• Most color disputes are illuminant metamerism, not bad dyeing: two samples match under simulated daylight and separate under store or office lighting.
• Name a primary illuminant plus at least one secondary illuminant in the spec. ASTM D1729 recommends CIE D65 as the daylight simulator for critical color appraisal.
• Use instruments to set tolerances and eyes to accept, not the other way around. AATCC EP6 governs instrumental measurement; AATCC EP9 governs visual assessment and requires observers to pass a color vision test.
• One color across three base fabrics is three lab dip programs, and each needs its own sealed standard.

What is a lab dip in performance knit fabric development?

A lab dip is a laboratory-scale dyeing of your production base fabric to a submitted color standard, produced so you can approve color before the mill commits a bulk dye lot. The mill dyes small swatches of the same construction, fiber blend, and weight you intend to buy, each against a recorded recipe, then returns them mounted and numbered for your decision.

A lab dip is not a paper chip or a fan deck reference. A color reference printed on paper or on a cotton pointer card tells the dyehouse where to aim; it does not tell you how the color will develop on a 240 g/m² polyester-spandex interlock. Dye uptake, surface texture, and light scatter all shift the result, which is why approval has to happen on textile, not on paper.

Print confirmation is a separate process with its own sample type and approval step. This article covers solid-dyed knit fabric only, from standard submission through sealed approval.

Why do approved lab dips still fail later?

Most rejected color is a lighting problem, not a dyeing problem. Two samples whose dye recipes use different colorants can match almost exactly under one light source and visibly separate under another; this is illuminant metamerism, and it is the single most common reason an approved lab dip looks wrong when garments reach a showroom, a retail floor, or a buyer’s office.

The reason is that a color measurement depends on the illuminant and the observer, not on the fabric alone. CIE 015:2018 Colorimetry defines the standard colorimetric observers and the standard illuminants, including D65, and those definitions are what both instruments and light booths are built around. Change the illuminant and you change the tristimulus values, so a pair that matched under one spectral power distribution can part under another.

Fluorescent whitening agents make this worse on light shades. Optical brighteners respond to the ultraviolet content of the light source, so whites and pastels shift between a booth with UV switched on and one with it off. Decide in advance whether UV is on during judgment and write it down.

What lighting and viewing conditions should a lab dip be judged under?

Judgment conditions belong in the specification, not in the dyehouse’s discretion. If the mill judges under D65 alone and your buyer reviews under TL84, you will both be reading the fabric correctly and still disagree. Naming a primary illuminant plus one or two secondary illuminants removes that argument before it starts.

ASTM D1729 sets out the equipment and procedure for visual appraisal of color and color differences on diffusely illuminated opaque materials, and recommends simulated average daylight as specified by the CIE for critical matching. It also makes observer qualification part of the method rather than an afterthought, which matters when several people on a development team take turns approving color.

AATCC EP9 covers the same ground specifically for textiles and specifies lighting and viewing geometry, specimen preparation, and observer screening; only observers who pass a color vision test may assess color difference under it. Those three requirements are the ones most often skipped in practice, and each of them changes the verdict:

• Specimen preparation. Remove wrinkles and folds, and mount the standard and the lab dip edge to edge with no gap, since a visible seam between them makes small differences harder to read.
• Orientation. Lay both pieces with the same fabric direction facing the same way. A brushed or raised surface changes lightness with nap direction, so a reversed swatch can fail a color it would otherwise pass.
• Observer screening. Confirm who on the team is qualified to sign color. Color vision deficiency is common enough that an unscreened approver introduces variability no tolerance can absorb, and AATCC EP9 treats screening as a condition of the method rather than good practice.

Should you approve color visually, instrumentally, or both?

Use both, with a clear division of labor: instruments set the tolerance, the eye makes the acceptance. Instrumental measurement gives you a number that two parties on different continents can agree on; visual assessment catches the things a single number cannot describe, such as surface sheen, texture, and nap direction.

AATCC EP6 is the reference procedure supporting instrumental color measurement in AATCC test methods, covering reflectance measurement, transmittance measurement, and the related calculations. In practice that means a spectrophotometer reading of the standard and the lab dip, converted into color difference values under each specified illuminant, recorded with the sample and not just reported verbally.

Tolerances have to name the equation, not only the number. A color difference figure is meaningless without the formula and the commercial factor behind it, and the same pair of samples can pass under one color difference equation and fail under another. Agree on the equation, its lightness-to-chroma ratio, and the acceptance value per shade depth, and record all of it on the approval document.

Instrumental grading can also replace some visual scale readings downstream. AATCC EP7 provides instrumental assessment of change in color as an alternative to visual gray-scale grading, though it excludes specimens treated in solutions containing fluorescent whitening agents. That distinction matters once you move into fastness testing, covered in our overview of AATCC testing for performance fabrics.

How does fabric construction change the same dye recipe?

The same recipe gives a different color on a different base fabric, so every base fabric in a program needs its own lab dip. Fiber content decides which dye classes are used at all; construction and weight decide how much light the surface scatters back; finishing decides what sits on top of the fiber when you look at it.

Fiber blends drive the hardest cases. A 100% polyester knit takes disperse dyes in a single class, a polyester-spandex blend adds a fiber that behaves differently in the same bath and can cross-stain, and a nylon-spandex construction moves into acid dyes entirely. Each combination has its own recipe, gamut limits, and fastness profile at depth, so a navy approved on one base does not transfer to another.

Stretch fabrics add a second viewing state. A legging dyed to an approved relaxed-state color reads lighter when extended, because the yarn spacing opens and more ground shows through, so judge high-elastane constructions both relaxed and at a representative extension. Our stretch fabric range spans both spandex and spandex-free constructions, and the two are treated as separate color programs.

Finishing sits between the dye bath and your eye. Brushing, raising, shearing, and heat setting all change surface geometry after the color is in the fiber, so a lab dip judged before the intended finish is not the color you will buy. Confirm the swatch carries the production finish route, a step covered in our walk-through of how performance fabric is made from yarn to finished textile.

What should you send the mill, and what should come back?

Incomplete submissions are the most common controllable cause of extra lab dip rounds. A dyehouse that receives a color reference with no base fabric, no judgment illuminants, and no tolerance is being asked to guess twice, and each guess costs a round. Send a complete package the first time.

What to send:

• A physical standard wherever possible, ideally dyed textile rather than a printed chip, with its identification code and the date it was issued.
• The base fabric item code for each construction in the program, so the mill dyes on the right substrate rather than a house base.
• The judgment conditions: primary illuminant, secondary illuminants, UV on or off.
• The tolerance: equation, commercial factor, and acceptance value, stated per shade depth if your range runs from pastels to blacks.
• Program context: how many colors, which garment categories, and whether the color is a carryover or seasonal, since carryover shades justify tighter control.

What should come back:

• Numbered swatches, each tied to a recorded recipe reference the mill can reproduce in bulk.
• Measured color data under each specified illuminant, not only a verbal “matched”.
• The judgment conditions the mill actually used, so you can tell whether a disagreement is about the fabric or about the booth.
• A note on achievability where a shade sits at the edge of what the dye class can reach on that fiber.

A sealed standard closes the loop. Record the base fabric item code, the approved recipe reference, the judgment illuminants, the tolerance, the approval date, and the named approver on the sealed sample itself, then store a retained duplicate in dark storage. Without that record, a bulk dispute six months later has nothing to arbitrate against. Fastness and dimensional stability testing then follow approval rather than replacing it, and once bulk starts the control problem shifts from matching a standard to holding consistency across dye lots.

How Mibein handles lab dips and bulk color

Mibein runs color development inside its own production chain rather than through a third-party dyehouse. Knitting, dyeing, and finishing are in-house, and the process route on the production side includes a color laboratory alongside greige inspection, singeing, washing and dyeing, and heat setting, so a lab dip is dyed on the same base fabric and finished through the same route as the bulk that follows.

Color judgment uses both instruments and eyes. The laboratory is equipped with a color matching light booth and a spectrophotometer-based digital color measurement system, and the workshop color stage is described as instrumental and visual color matching, which matches the division of labor described above: measured data to set the boundary, trained observers to accept inside it.

Control continues after approval. Each dye lot is checked for color consistency, fabric weight, width, handfeel, and functional performance, and fabric appearance is inspected before shipment using the US Standard 100-yard fabric grading system, the 4-point system. That batch-level color check is what connects an approved lab dip to the rolls that arrive at a cutting table. The sequence is visible in the workshop gallery.

Two routes exist for getting to an approved color, and they differ in how much color development is needed. Custom co-development starts from your standard and your brief, running through Mibein’s five-stage project flow: project discussion, solution matching, sampling and evaluation, optimization and confirmation, and bulk supply execution. Ready fabric programs instead start from existing color cards and ready meter samples on market-proven constructions, and selected programs let a brand move without additional color development cost; selected greige inventory also shortens dyeing lead times, with actual timing confirmed per program rather than quoted as a fixed number. Both routes are described on the services page, and the choice between them usually comes down to how distinctive the color needs to be against how fast the collection has to move.

Teams running several base fabrics in one palette should ask for every construction to be lab dipped at once rather than sequentially. Sampling and material evaluation support for that kind of program sits on the product development team page.

FAQ

Bottom line: a lab dip only settles color if the specification around it is complete. Fix the base fabric, name the illuminants, state the tolerance equation, screen the approver, and seal the standard with all of it recorded. Do that and color approval becomes a short, repeatable step instead of the stage that delays the collection.