Carpet Fiber Deep Reference
Why this matters
Fiber identification is the technical foundation of carpet cleaning. The wrong chemistry on the wrong fiber destroys the carpet within minutes - alkaline on wool, oxidizer on olefin, hot water on silk. The IICRC fiber-ID test is industry-standard practice; the tech who can ID by sight + burn test + chemistry test in 60 seconds prevents the ruined-carpet claim.
Major fiber categories
Synthetic fibers (80% of US residential carpet)
Nylon (polyamide) - the workhorse
- Most common residential + commercial carpet fiber
- Two types: Type 6 (Allied Caprolactam) + Type 6.6 (DuPont/INVISTA Antron). Type 6.6 has tighter molecular structure, better resilience.
- Pile crush recovery: excellent
- Stain resistance: factory-treated; degrades over years (consumer-grade) OR engineered-in (commercial-grade)
- pH tolerance: 4 - 10 (wide range; most cleaners work)
- Heat tolerance: melts above 480°F
- ID: white burn ash; "celery" smell when burned; melts to bead
Polyester (PET)
- Growing residential share; affordable + soft
- Pile crush recovery: moderate (worse than nylon)
- Stain resistance: inherent (oil-based fiber repels water-based stains)
- pH tolerance: 4 - 10
- Heat tolerance: melts above 480°F
- ID: black smoke; "sweet" smell when burned; hard bead
Olefin (polypropylene)
- Common in commercial loop carpet, indoor-outdoor
- Pile crush recovery: poor
- Stain resistance: inherent (water-based stains roll off)
- pH tolerance: 4 - 10
- Heat tolerance: SENSITIVE to heat - melts at 320°F. Use lower extractor temp.
- Susceptible to oil-based staining + UV degradation
- ID: black smoke; pungent smell when burned; molten chunk
Acrylic + modacrylic
- Mostly in older rugs + bath mats; rare in modern carpet
- pH tolerance: 5 - 8
- Heat tolerance: moderate
- ID: burns + sustains flame; black smoke
Natural fibers (15 - 20% of US carpet, premium tier)
Wool
- Premium residential; commercial in high-end hospitality + offices
- Pile crush recovery: excellent
- Inherent flame resistance + stain resistance (lanolin)
- pH tolerance: 5 - 7.5 (acid-side ONLY; alkaline >8 damages protein structure)
- Heat tolerance: tolerates moderate heat; HOT water + alkaline = damage
- ID: burning hair smell; ash crumbly + gray; flame self-extinguishes
Cotton
- Common in flatweave rugs + small area rugs
- Often used as foundation in oriental rugs
- pH tolerance: neutral to mild alkaline (5 - 9); avoid strong acid (degrades)
- Heat tolerance: tolerates high heat
- ID: burns easily with paper-like smell; gray ash; "browning" risk when wet + heated (cellulose degradation)
Silk
- Premium; specialty work
- Pile crush recovery: minimal (silk pile crushes permanently)
- pH tolerance: 5 - 7 (very narrow; acid-side; gentle)
- Heat tolerance: low; never hot water
- ID: burns slowly with hair smell; ash blackish; very fine pile
Sisal + jute (plant fibers)
- Floor covering material, not carpet per se
- pH tolerance: neutral only
- Heat tolerance: tolerates moderate heat
- Water sensitive: WET sisal stretches + curls + browns. Dry cleaning ONLY for sisal.
Carpet construction types
Tufted
- 90%+ of US residential carpet
- Yarn punched into backing fabric, glued with latex secondary backing
- Loop pile OR cut pile
- Most cleaning methods work; truck-mount + hot water extraction standard
Woven
- Premium residential + commercial; Wilton, Axminster, Velvet
- Yarn woven INTO the foundation
- More durable; higher price point
- Most cleaning methods work; less risk of delamination
Needle-punched
- Indoor-outdoor + commercial-grade
- Fibers entangled mechanically with no backing latex
- Very durable; tolerates hot water + aggressive chemistry
Knotted (oriental rugs - separate SOP)
- Hand-knotted construction
- Foundation cotton OR wool
- Pile typically wool OR silk
- Specialty chemistry required
Identification tests
Visual + tactile
- Wool: warm to touch, slightly elastic, irregular fiber
- Synthetic: smooth, consistent diameter
- Cotton: soft, matte
- Silk: lustrous, very fine
Burn test (last resort; do NOT damage customer's carpet)
- Take a small fiber sample (cut from concealed area or already-shedding fiber)
- Hold with tweezers; apply flame briefly
- Observe: smell, flame behavior, ash type
| Fiber | Smell | Flame | Ash |
|---|---|---|---|
| Wool | burning hair | self-extinguishes | crumbly gray |
| Nylon | celery | melts + drips | white bead |
| Polyester | sweet | melts + drips + black smoke | hard bead |
| Olefin | pungent | melts | molten chunk |
| Cotton | paper | sustains flame | soft gray ash |
| Silk | burning hair | slow burn | blackish |
Chemical test (the IICRC field test)
- Apply small drop of household bleach to fiber
- Wool + silk: dissolve in 1 - 2 minutes (protein fibers)
- Cotton + synthetic: unchanged
Chemistry by fiber
- Wool: pH 5 - 7.5 (acid-side; never above 8); cool to tepid water; gentle agitation; fast drying. Wool-specific cleaners: Bridgepoint Maxim Advanced Wool, ProsChoice Wool Pre-Spray.
- Nylon: pH 4 - 10; standard chemistry; hot water extraction works.
- Polyester: pH 4 - 10; less responsive to standard chemistry (inherent stain resistance); hot water OK; brushing helps matted pile.
- Olefin: lower extractor temp (under 180°F); pH 4 - 10; susceptible to oil staining; color heat-sensitive.
- Cotton: cool to tepid; pH 5 - 8; "browning" risk with heat + alkaline + slow dry; vinegar rinse prevents.
- Silk: cool water only; pH 5 - 7; acid-side; minimal agitation; refer to specialist if unsure.
The IICRC bleach test is the fastest single fiber-ID in the field. A drop of household bleach on a fiber: wool + silk dissolve (protein); cotton + synthetic don't. This 60-second test prevents most chemistry mistakes + tells you what type of cleaner to use BEFORE you've touched the customer's carpet. Carry a small bottle of bleach + a piece of white tile (clean surface for the test) in every kit.
Fiber + chemistry decision matrix
| Symptom | Likely fiber | Approach |
|---|---|---|
| Yellow tint after cleaning | wool with alkaline | acid rinse to neutralize |
| Browning lines | cotton with heat | cool water + acid rinse |
| Melted/matted appearance | olefin with hot extractor | lower temp; replace if severe |
| Dye bleed | wool or silk with hot water | cold + acid rinse |
| Crystallized stiff feel | wool with detergent residue | rinse + acid rinse |
| Furred surface | low-twist nylon | proper rinse + grooming |
References
- IICRC S100 Standard for Professional Cleaning of Textile Floor Coverings
- CRI Seal of Approval program (equipment + chemistry certification)
- WoolSafe Approved Service Provider
- Manufacturer fiber care guides (Shaw, Mohawk, Stainmaster, Karastan)
- Manuall internal: Standard Hot Water Extraction Service, Hand-Knotted Oriental Rug Specialty Cleaning