Field Fiber Identification - Burn Test and Visual ID
Why this matters
Carpet and upholstery cleaning chemistry is fiber-specific. The wrong chemistry on the wrong fiber damages the carpet - yellowing on wool from alkaline cleaners, melting on olefin from aggressive heat, color migration on nylon-acid-dyed carpet from improper pH. The customer's installation paperwork, when available, identifies the fiber, but that paperwork is missing for most jobs. The field burn test is the carpet cleaner's reliable fiber-identification tool - 30 seconds, a small sample, a lighter, a damp paper towel, and you know what you're cleaning. This article covers the burn test and the supporting visual identification.
When to use this procedure
- Pre-cleaning fiber verification on any carpet without confirmed identification
- Pre-cleaning verification on upholstery (often more variable than carpet)
- Identification of mystery materials at restoration jobs (clothing, drapes, bedding)
- Confirming a sample from a carpet patch matches the main installation
- Customer education when the customer asks "what is my carpet made of?"
Always pull a sample from an inconspicuous area - under furniture, inside a closet, from a small unobtrusive cut. Some carpets blend fibers within a single yarn; pull from multiple locations if first test gives ambiguous results.
Tools and materials
- Tweezers
- Butane lighter
- Damp paper towel
- Aluminum pie pan or non-flammable surface to perform the test on
- Sharp scissors
- Phone for photographing the sample before and after
- Comparison chart (this article serves as one)
Safety
Synthetic fibers melt and drip when burned. Drip hot melted fiber falling on skin causes severe burns. Perform the test over a non-flammable surface, away from the customer, with a damp paper towel ready to extinguish. Do NOT perform on the carpet itself - pull a sample free first.
Ventilate the area; some burning fibers produce acrid fumes. The test produces minimal smoke if performed correctly (small sample, brief flame) but ventilation is good practice.
The burn test procedure
Step 1: Pull a sample
- Identify an inconspicuous area
- Pull or carefully clip a single yarn (the entire pile tuft - usually 1/2 inch in length is enough)
- Set on a non-flammable surface
Step 2: Hold the sample with tweezers
- Grip the sample by one end with tweezers
- The other end is the "test" end
Step 3: Light the test end
- Bring the lighter flame to the test end of the sample for 1-2 seconds
- Withdraw the flame
- Observe:
- Does the fiber continue burning? Sputtering? Self-extinguish?
- What does the smoke smell like?
- What does the burned end look like? (Crispy ash? Hard bead? Soft residue?)
- Does the fiber drip while burning?
Step 4: Compare against the chart
The combination of behaviors identifies the fiber:
| Fiber | Burn behavior | Smell | Residue |
|---|---|---|---|
| Wool | Sputters, self-extinguishes when flame removed | Burning hair / feathers | Soft, crushable black ash |
| Silk | Burns slowly, sometimes self-extinguishes | Burning hair (lighter than wool) | Soft black ash, easily crushed |
| Cotton | Burns readily, continues after flame removed | Burning paper / leaves | Light gray powdery ash |
| Linen | Burns readily, similar to cotton | Burning paper | Gray ash |
| Nylon (polyamide) | Melts, slowly burns; drips | Celery / vegetable burning | Hard black bead, smooth |
| Polyester (PET) | Melts, burns slowly; drips | Sweet chemical / fruity | Hard black or brown bead |
| Olefin (polypropylene / PP) | Melts immediately, burns slowly; drips | Asphalt / wax | Hard tan or black bead |
| Acrylic | Burns rapidly, melts; flares up | Acrid chemical, sharp | Hard black irregular bead |
| Triexta (PTT) | Melts and burns, similar to polyester | Mild chemical | Hard black bead |
| Rayon / viscose | Burns rapidly like cotton | Burning paper (slightly chemical) | Light gray ash |
Visual identification (before burn test)
Sometimes the carpet's appearance and feel narrow the options before testing:
Wool:
- Springy, resilient pile that bounces back from compression
- Often used in high-end residential and commercial
- Color may be slightly variegated within a single shade
- Natural sheen, not glossy
- Premium installations often have wool
Nylon:
- The most common synthetic in residential carpet (80%+ of US residential)
- Strong, springy, takes color well
- Wears the longest of synthetics
- Loose individual yarns under inspection
- Often labeled "Stainmaster," "Permanent stain treatment," "ScotchGard treated"
Polyester (including PET):
- Soft hand-feel, often softer than nylon
- "Solution-dyed" or "PTT" labeling on modern installations
- Resists water-based stains well
- Doesn't return from compression as well as nylon
Olefin (polypropylene):
- Lower-cost residential and outdoor carpets
- Resistant to most water-based stains AND most chemistries
- Heat-sensitive (avoid hot extraction; can crush or melt)
- Often used for berber-style loop carpets
Acrylic:
- Less common in modern carpet; used in some specialty installations
- Wool-like feel
- Burns hot and fast in the test
Triexta (PTT):
- Mohawk's SmartStrand brand and similar
- Increasingly common in mid-tier residential
- Hybrid characteristics - feels like polyester, performs like nylon in some respects
- Solution-dyed; excellent stain resistance
Cleaning chemistry by fiber
| Fiber | Cleaning approach | Avoid |
|---|---|---|
| Wool | Slightly acidic pH (5.5-7.5); cool to warm water; gentle agitation | High pH (above 9); high heat; aggressive bleaches; benzyl alcohol solvents |
| Silk | Specialty cleaner; cool water; minimal agitation | Hot water; any alkaline; strong solvents |
| Cotton | Wide pH tolerance; warm water | Avoid extreme heat causing shrinkage |
| Nylon (acid-dyed) | pH 6-10; high heat; standard pre-spray | Strong acids (color migration); long-dwell solvents |
| Nylon (solution-dyed) | Wide tolerance; hot water; aggressive chemistry OK | Very few constraints |
| Polyester | Hot water; oil-cutting chemistry (polyester attracts oily soil) | Mild constraints; avoid extreme alkaline on PET |
| Olefin | WARM (not hot) water; oil-cutting chemistry; gentle suction | Heat above 200 °F; the fiber melts |
| Acrylic | Warm water; mild chemistry | Strong heat; aggressive solvents |
| Triexta | Wide tolerance; hot water; aggressive chemistry | Few constraints |
Color-test before cleaning
For any unknown carpet, perform a color-fastness test BEFORE the burn test diagnosis is acted on:
References
- IICRC S100 - Standard for Professional Cleaning of Carpet
- CRI (Carpet and Rug Institute) Cleaning Standard
- ASTM D276 - Standard Test Method for Identification of Fibers in Textiles
- Manufacturer technical bulletins on fiber properties (Mohawk, Shaw, Stainmaster, etc.)
- Manuall internal: Carpet Fiber Deep Reference, Fiber ID Care Chart, Hot Water Extraction Service SOP