Guide · For the trade
Carpet dye lot: what it is, why two rolls of the same color differ, and how to keep a job in one lot
A carpet dye lot is the batch of yarn or carpet that went through the dye range together, and the mill guarantees a color match only within that one batch. Two rolls of the same style and color from different lots can differ by a visible half shade, which is why a whole project should be ordered on one purchase order, cut from one lot, and confirmed with a cutting for approval before the roll ships.
This guide is for the designer or the junior who has just been asked why the hall does not match the bedroom. It covers what a dye lot is, how much variation is normal, how to order so the job lands in one lot, what to check on delivery, and what can be done after the fact. The ordering broadloom guide covers the order itself; this one covers the color.
What does dye lot mean on a carpet spec?
Most carpet is colored in one of three ways. Piece-dyed carpet is tufted white and dyed as a finished roll, so every roll in a run is a lot. Yarn-dyed carpet, including most Wilton and Axminster, is woven from yarn dyed in a batch, so a woven pattern can carry three or four lots at once, one per color. Solution-dyed fiber has the pigment in the polymer before extrusion, so the color holds from one run to the next and the lot matters far less. On a roll ticket the lot appears as a dye lot, shade, batch or run number next to the style and color, and that number, not the color name, is what the installer checks on every roll before cutting.
How much variation is normal
Mills work to a commercial color tolerance measured on a spectrophotometer, and a roll within tolerance is a roll the mill will not replace. In practice a difference of about half a shade is possible from lot to lot, invisible on a pom and visible along a seam under a window. Within one lot a well-made seam disappears in a cut pile. A different lot can also read darker with the same dye, because the finishing and the way the pile lies changed with the batch.
| Coloring method | Where the lot is | Lot-to-lot risk | Typical constructions |
|---|---|---|---|
| Piece dyed | The finished roll | Highest; solid colors show it most | Tufted cut pile and loop in nylon, polyester, wool |
| Yarn dyed | The yarn batch, one per color | Moderate; a pattern hides a small shift | Wilton, Axminster, woven wool loop |
| Solution dyed | The fiber run | Lowest; near-identical between runs | Solution-dyed nylon and polypropylene, most outdoor and commercial lines |
| Hand-made rugs | The dye pot, per color | Expected; abrash is part of the look | Hand-knotted, hand-loomed and hand-tufted wool |
A solid, light, piece-dyed cut pile is the carpet most likely to show a lot change. A multi-tone patterned loop or a solution-dyed nylon rarely does.
Ordering the whole job in one lot
The only reliable protection is to order everything at once. The sequence that works is short.
- Measure every room, stair and closet that will take the carpet, including later phases, and order the total on one purchase order.
- Ask for a cutting for approval, a CFA, on any solid or light color. The mill cuts a swatch from the roll it plans to ship; check it against the approved sample in daylight and sign it off in writing.
- If the yardage needs more than one roll, ask that both come from the same lot. A job that cannot be filled from one lot is laid out so each lot stays in its own rooms, with the change at a doorway, never at a seam mid-floor.
- Add 5 to 10 percent for attic stock from the same lot, labeled by room.
Phased projects are where lots go wrong. A client who carpets the upstairs this year and the stair next year should be told now that the stair will not match; order the stair yardage now and hold it, or plan a deliberate change of color at the landing.
What to check on delivery day
Before the first cut, the installer unrolls each roll in the room where it goes, in daylight, and lays the approved sample or the CFA on the pile. Every roll ticket should carry the same lot number as the CFA. If one does not, it does not get cut; a cut roll cannot go back to the mill, and the claim closes the moment the knife goes in. Photograph the tickets on the pile. The installation checklist puts this step in the order of the day.
Rug color variation: abrash, and why it is not a defect
Hand-made wool rugs are dyed in small pots, and the slight horizontal banding where one pot of yarn gave way to the next is called abrash. In a Tibetan, Oushak or tribal weave it is the signature of the hand and the reason a rendering says the color will vary; the same applies to vegetable dyes, overdyed pieces and undyed natural wool. The strike-off shows the color family and the construction; the finished rug shows it with abrash. A stripe of a different hue across the full width, or a border that does not match the field, is a production error, not abrash, and goes back.
Why does the carpet look different in different rooms?
Not every mismatch is a lot problem. Pile direction is the usual cause: carpet laid with the pile toward a window reads lighter than the same roll laid away from it. Light is the second: a north bedroom and a south hall show the same gray differently. Only when the pile runs the same way, the light is comparable and the roll tickets show different numbers is it a dye lot difference, and then the claim is made on the uncut rolls.
Questions designers ask
What is a dye lot in flooring?
A dye lot is the batch of material that was colored together, whether yarn in a vat or a finished roll on a dye range. Carpet, tile, vinyl and wood finishes all carry one. The manufacturer guarantees a color match inside the lot and only a commercial tolerance between lots, which is why the whole job is ordered at once and the lot numbers are checked on delivery.
What does dye lot mean on a roll ticket?
The number beside the style and color that identifies the batch the roll came from. Every roll on one job should show the same number as the CFA. A different number on one roll means that roll goes in its own room or goes back before it is cut.
Can a carpet be re-dyed on site to fix a color difference?
On-site dyeing works on nylon and wool, which take acid dye, and can darken a mismatched area toward its neighbor; it cannot lighten a color and does not work on polyester, polypropylene or solution-dyed fiber. It is a last resort for an installed job, and the result is a near match, not a mill match.
What drives the cost of dyeing carpet on site?
The fiber, the area and the size of the color change. A small area blended to match a neighbor is straightforward; a whole room shifted several shades is a day of specialist work. On most projects, replacing the room from the original lot's attic stock is faster and more predictable than dyeing.
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