Views: 1 Author: Site Editor Publish Time: 2026-11-10 Origin: Site
When a hook and loop tape ends up on a finished product, the buyer rarely sees the tape on its own. They see it next to dyed fabric, moulded plastic or printed packaging. That is why a shade that looks acceptable on a sample card can still trigger a rejection three months later, once the tape and the surrounding parts sit side by side on a production line.
Treating colour as a written specification, with a number attached, removes most of that argument. This article covers where colour variation comes from, how to measure it, what tolerance bands are realistic, and what to sign off before the first bulk order.
In woven and knitted hook and loop, colour is introduced in one of two ways.
Yarn dyeing colours the filament or spun yarn before weaving. The tape keeps a more uniform appearance across the surface, and the hook side and loop side can be matched more closely, because both are built from yarns of the same dye bath. The trade-off is a minimum quantity per colour, since a dye vessel has to be filled.
Piece dyeing colours the finished roll. It is more flexible for small runs and unusual shades, but tension and density differences in the web can show up as subtle streaks, and the hook side and loop side may shift slightly differently.
Either route produces dye lots. A dye lot, often called a kettle or bath number, is a single run of material coloured together. Two lots of the same recipe are never identical. The question is not whether they differ, but by how much and whether that difference matters for the application.
Delta E (ΔE) expresses the distance between two colours in a perceptual colour space. It is the number that turns a shade argument into a pass or fail.
Three practical points decide whether two ΔE values are comparable.
The formula matters. ΔE*ab (CIE76) is the oldest and the most forgiving in some regions of colour space; ΔE00 (CIEDE2000) tracks human perception more closely, particularly for blues and dark shades. A supplier reporting 1.0 with CIE76 is not making the same claim as a supplier reporting 1.0 with CIEDE2000. State the formula in the specification.
The instrument geometry matters. A 45/0 or 0/45 instrument reads texture differently from an integrating sphere. Hook and loop is a textured, pile surface, so the reading depends on how the sample is presented. Use the same instrument type, the same aperture and the same number of readings on both sides.
The illuminant and observer matter. D65 with the 10-degree observer is the usual convention for textile shade approval. If one party measures under D65 and the other under A or F11, the numbers will diverge and the discussion will go nowhere.
A measurement protocol that survives an audit usually specifies all four: instrument model, geometry and aperture, illuminant and observer, and the number of readings averaged per sample with the sample folded or layered to opacity.
Published tolerances are only useful if they match what the process can actually hold. The bands below are common practice for dyed hook and loop in industrial supply; the right band for a given project depends on how the tape will be used.
Application context | Typical ΔE00 band | What drives the choice |
|---|---|---|
Internal or hidden fastening, no colour match required | 2.0 or wider | Function only; colour is not a visible attribute |
Visible trim, consumer goods, bags and apparel | 1.0 to 1.5 | Adjacent to dyed fabric; customer notices stacking |
Colour-critical brand goods, automotive interior | 0.8 to 1.0, plus lot approval | Large visible areas; multi-lot builds on one line |
Matched set: tape, webbing and thread in one shade | 0.8 or tighter, one lot only | Different substrates under one shade name |
Two cautions. First, a tight band agreed on paper is worthless if the supplier cannot hold it, because every shipment becomes a negotiation. Second, a tight band on the hook side and a loose band on the loop side is a common oversight: they are different surfaces and both are visible when the fastener is open.
Shade approval is a physical process, not an email exchange of photographs. A workable sequence looks like this.
Step one: define the target. Either a physical standard from the customer, or a colour reference such as a Pantone textile number, or both. If both exist, state which one governs when they disagree.
Step two: submit a lab dip or a sample length. The supplier produces a small quantity against the target and measures it, reporting ΔE00 against the governing reference with the instrument details.
Step three: view under controlled light. A light booth with D65, TL84 and horizon light, plus a viewing box, shows whether the match holds across the conditions the product will actually be seen in. Two samples that match under D65 can drift apart under retail lighting; that is metamerism, and it is a pigment problem, not a measurement error.
Step four: sign and retain. The approved sample is signed, dated, given a lot reference and kept by both parties. Bulk shipments are then compared against that retained standard, not against a screen image or a memory.
Step five: record the lot. Each shipment carries its dye lot number on the label and on the packing list. When a customer reports a mismatch two months later, the lot number is what makes the investigation possible.
An approved shade can still move during converting. Four causes account for most surprises.
Coating and adhesive. An adhesive coating or a flame-retardant back-coating can shift the apparent shade, partly through the film itself and partly through how the surface reflects light. Approve the shade on the coated product, not on greige tape, if the tape will be coated.
Heat exposure. Thermosetting, heat sealing and drying can yellow pale shades and deepen saturated ones. If the part will be heat processed, include a processed sample in the approval.
UV and ageing. Pale shades and certain reds are sensitive to light. Where the product spends its life outdoors or near a window, a lightfastness grade belongs in the specification alongside ΔE.
Surface texture. A brushed or raised loop reads lighter than a flat loop of the same dye. If the construction changes between orders, the shade reference has to follow the construction, not just the recipe.
A colour clause that holds up in a claim usually contains the following items. Each one closes a specific gap.
Governing reference: physical standard number, Pantone textile reference, or both, with a precedence rule
Colour space and formula: CIELAB values with ΔE00, illuminant D65, 10-degree observer
Instrument: model, geometry, aperture, readings per sample
Tolerance: separate bands for hook side and loop side, and for the coated product
Lot control: one lot per purchase order for matched sets; lot number stated on label and packing list
Retained standard: who holds it, when it expires, how it is replaced
Lightfastness: grade and test method where the product is exposed to light
Inspection point: whether colour is checked on greige, coated or converted goods
The most useful thing a buyer can do is to send the actual adjacent material with the enquiry, not a colour name. A 50 mm square of the fabric the tape will sit against removes more ambiguity than any adjective.
It also helps to say what happens if the shade is off. A cosmetic mismatch on a hidden fastener may be acceptable at ΔE 2.0; the same number on a visible trim panel may not be. Suppliers plan tooling, dye lots and inspection effort around that answer, and a buyer who states it up front usually gets a more honest tolerance proposal in return.
Where a programme runs for years, agree a re-approval interval. Pigments age, standards drift, and a retained sample from three years ago is a poor referee for a shipment made today.
