Wool vs Nylon vs Polyester Cleaning Method Decision Tree

Why this matters

The biggest single source of avoidable damage claims in residential carpet work is using a nylon protocol on wool. A high-alkaline pre-spray that is safe and effective on nylon 6 will dissolve the disulfide bonds in wool, yellow the fiber, and shrink the carpet measurably; the damage is permanent and the cost is replacement, not refund. Equally, using a wool-safe acid prespray on a polyester traffic lane will under-clean and pull the customer back at 30 days. Method selection has to be deterministic, and it starts with positive fiber identification, not assumption.

Symptom presentation

You are at a cleaning, not a complaint. The presenting question is which method to deploy. The risks of getting it wrong are color loss, dye bleed, fiber damage, dimensional change, under-cleaning, residue, and callback. The four common fiber families to identify are wool (cellulosic-feeling, scaled fiber, burns to charred smell of hair), nylon (the most common synthetic, melts to a hard bead, burns with celery-like smell), polyester (PET) including triexta, and olefin (polypropylene). Misidentification is most common between nylon and PET because they look similar to the eye.

Quick checks at the door

Run a burn-test ID before chemistry decisions if the customer cannot produce manufacturer documentation. Snip a 3 to 5 fiber sample from a hidden area (under furniture, inside a closet, against the tackstrip), hold with metal tweezers, ignite with a butane lighter, observe flame behavior, smell the smoke, and inspect the residue. Wool self-extinguishes, smells of burnt hair, leaves a crushable ash. Nylon melts, smells of celery, leaves a hard gray bead. Polyester melts, smells sweet, leaves a hard dark bead. Olefin melts at low temperature, smells like candle wax, leaves a hard bead and floats on water. Confirm wool with a sodium hypochlorite drop test (wool dissolves in 5 percent bleach within 30 minutes; synthetics do not).

Isolation tree

Branch wool: any positive burn-test indication of wool, any documentation showing wool, any felted-look construction, or any Berber with a distinctive lanolin smell. Pre-spray must be wool-safe (pH 4.5 to 8.5 max, acid side preferred), no high-alkaline, no oxygen bleach, no enzymatic strong enough to attack the protein. Solution temperature 105 F maximum (40 C). Rinse with acid rinse at pH 4.5 to 5.0. Dry within 4 hours to under 12 percent moisture content. Branch nylon (positive burn-test of nylon, including the dominant residential family): pre-spray can range pH 9 to 11 for soiled traffic lanes, solution temperature up to 170 F (76 C) safe, acid rinse to set dye, normal dry. Branch polyester PET and triexta: oleophilic fiber that holds oils tightly; pre-spray pH 9 to 11 with an oily-soil-emulsifying surfactant, mechanical agitation is essential (a rotary brush will outperform pure HWE), solution temperature 200 F (93 C) for stubborn oily soil, acid rinse, weighted dry. Branch olefin: hydrophobic, oleophilic, low melting point; pre-spray pH 9 to 11 with oily-soil emulsifier, solution temperature 180 F (82 C) max to avoid melt-fusion, acid rinse, monitor for crushing during agitation.

Confirming diagnosis

Wool confirmation requires two positive tests (burn + bleach) before you commit chemistry. Nylon confirmation by burn-test alone is acceptable for routine work because nylon-safe chemistry is also safe on most synthetics. Polyester vs olefin is distinguished by the float test (olefin floats in water, polyester sinks). Triexta (PTT) is biologically derived but behaves chemically like polyester for cleaning purposes. When in doubt about wool versus a wool-like synthetic, default to the wool protocol; the cost of overcautious cleaning is a slightly slower clean, not damage.

Remediation

Wool protocol: dry vacuum thoroughly (wool sheds, vacuuming is most of the soil removal), acid-side pre-spray at labeled dilution, dwell 10 minutes, hot-water extract at 105 F maximum with acid rinse, dry aggressively. For wool spot work, do not use oxygen bleach products; use protein-safe spotters. Nylon protocol: dry vacuum, alkaline pre-spray for traffic lanes, dwell 10 to 15 minutes, hot-water extract at 170 F with acid rinse, normal dry. Nylon tolerates rotary scrubbing on heavy soil. Polyester protocol: dry vacuum, alkaline pre-spray with oily-soil emulsifier, mechanical agitation with a counter-rotating brush, dwell 15 minutes, hot-water extract at 200 F with acid rinse, weighted dry. Set customer expectations that polyester traffic lanes look "clean" but never fully return to new because permanent compression-set develops earlier than on nylon. Olefin: same as polyester but with the temperature ceiling and crush watch.

References

• IICRC S100-2023 Standard for Professional Cleaning of Textile Floor Coverings, fiber-specific cleaning sections
• IICRC S300-2017 Standard for Professional Upholstery Cleaning, fiber identification protocols
• Carpet and Rug Institute Carpet Cleaning Industry Reference Series, fiber chemistry and pH tolerances
• WoolSafe Organisation approved product list and protocols, current revision