Which Test First Fiber ID vs pH vs Colorfastness On Unknown Carpet Sequencing Decision Tree

Why this matters

On an unknown carpet, the order you run your pre-tests is not arbitrary - run them out of sequence and you can ruin the carpet with the very test that was supposed to protect it. Fiber identification must come first because it tells you which chemistry is even safe to test with: a high-pH colorfastness swab on wool can brown the fiber and bleed the dye in the same stroke. pH and colorfastness are downstream of knowing what you are standing on. This tree fixes the sequence and gives the go/no-go branch points so you never apply a product the fiber cannot tolerate.

Symptom presentation

You are quoting or starting on a carpet with no documentation: no fiber tag, unknown age, unknown prior treatments, possibly a wool or wool-blend area rug, possibly solution-dyed nylon, possibly an olefin/PET builder-grade. The risk is that aggressive default chemistry browns wool, bleeds a non-colorfast dye, or yellows an installation. You need a safe, ordered pre-inspection.

Quick checks

Before any chemical touches the carpet:

1. Walk and read the room - matting, traffic lanes, visible delamination, prior repairs.
2. Tuft pluck for a burn test - a single tuft from an inconspicuous edge.
3. Hot pin / feel - natural fibers feel different from synthetics; this primes the fiber ID.
4. Locate an inconspicuous test area - inside a closet, under furniture - for the wet tests.
5. Dry vacuum first - never wet-test over loose soil that masks the result.

Isolation tree - the correct sequence

Step 1 (always first) - FIBER IDENTIFICATION. Run the burn test on a plucked tuft and confirm with feel/melt behavior:

• Wool: smells like burning hair, self-extinguishes, crushable gray ash. Flags the entire job as low-pH only.
• Nylon: burns and melts, celery-like smell, hard bead. Tolerant of a wide pH band.
• Polyester (PET): melts, sweet/chemical smell, hard black bead. Oil-loving soil; moderate chemistry.
• Olefin/polypropylene: melts readily, waxy/asphalt smell, floats in water. Heat-sensitive; oil-attracting. You cannot choose a test chemistry until this branch resolves, because the fiber sets the pH ceiling.

Step 2 - pH SELECTION (driven by Step 1). Now pick your candidate cleaning chemistry within the fiber's tolerance, then verify the carpet's existing pH:

• Wool and wool-blends: stay acid to neutral (roughly pH 5 to 8). Alkaline products risk browning and dye bleed.
• Nylon/PET/olefin: synthetics tolerate higher alkalinity, but match it to soil, not habit. Strip-test a damp swab of the carpet itself - a high reading can reveal a prior alkaline residue you must rinse before cleaning.

Step 3 - COLORFASTNESS (with the chemistry chosen in Step 2). Only now test dye stability, using the actual product you intend to use at working dilution:

• Apply to a white towel pressed on an inconspicuous spot for a timed dwell; check for dye transfer.
• Test in multiple colors if the carpet is patterned - a dark band can bleed when the field does not.

Why the sequence cannot be reordered. The temptation is to colorfast-test first because dye bleed is the visible failure customers blame you for. But colorfastness is meaningless until you know the chemistry you will actually use, and you cannot choose chemistry until you know the fiber. Run colorfastness before fiber ID and you either test with a product you will not use (no information) or test with an aggressive default that itself damages the fiber. Likewise, a pH reading on the carpet is only actionable once the fiber sets the acceptable band - a pH of 9 is a problem on wool and routine on nylon. Fiber, then pH band, then colorfastness with the chosen product: each step supplies the input the next one needs.

Confirming diagnosis

• Fiber confirmed when the burn signature plus float/melt agree (e.g., self-extinguishing + hair smell + crushable ash = wool).
• pH path confirmed when the carpet swab reads within the band you expect and the chosen product sits inside the fiber's tolerance.
• Colorfastness confirmed when the white towel shows no dye transfer after the full intended dwell, in every color present. If any step fails, you stop and re-select chemistry rather than proceeding.

Remediation / proceeding

• All three pass: clean with the verified chemistry at the verified dilution.
• Fiber = wool, colorfast on low-pH: proceed with WoolSafe-appropriate low-pH chemistry, control moisture and dry fast to avoid browning.
• Colorfastness fails: drop to a milder/lower-pH product or a low-moisture method, re-test; if it still bleeds, advise the customer of the limitation in writing before cleaning.
• Ambiguous fiber: treat as wool until proven otherwise.

References

• IICRC S100, Standard for Professional Cleaning of Textile Floor Coverings - pre-inspection, fiber identification, pH, and colorfastness testing sequence.
• WoolSafe Organisation - approved low-pH chemistry and browning-risk guidance for wool.
• Carpet and Rug Institute (CRI) Seal of Approval - product/fiber compatibility criteria.