Burn Testing and Solubility Spot Testing

Why Burn Testing and Solubility Spot Testing Matter

Before you press, clean, or apply any solvent to a garment, you need to know what it is made of. Fabric labels can be missing, faded, or misleading, and blends complicate things further. Two low-cost, hands-on methods — the burn test and the acetone solubility spot test — let you gather physical evidence about fiber content right at the point of care. Both methods are taught and referenced by the Drycleaning & Laundry Institute (DLI) as part of professional fiber identification practice.

Safety First: PPE and Work Area Requirements

These tests involve open flame and a flammable solvent. Neither is optional, and neither is casual. Before you touch a lighter or open an acetone bottle, the following controls must be in place:

• Safety glasses — protect against flame flash and solvent splash at all times during the lab.
• Heat-resistant gloves — worn when holding the burn-test tray or tweezers near a flame.
• Lab coat — protects skin and personal clothing from both sparks and solvent contact.
• Ventilation — acetone vapor is flammable and can irritate airways. Work under a fume hood, near an exhaust fan, or outdoors. Never use acetone near an open flame.
• Metal burn-test tray over a ceramic surface — contains ash and prevents heat transfer to the work surface.
• Fire extinguisher location — know where it is before the lab begins. The correct type for a solvent fire is a CO₂ or dry-chemical extinguisher rated for Class B fires.
• No PPE, no lab — if you are found handling flame or solvent without full PPE, you stop immediately, repeat the safety briefing, and re-test.

Lockout/tagout does not apply to this bench lab, but the principle behind it — controlling the hazard before you work — is exactly what donning PPE before touching any material represents.

The Burn Test: What to Do and What to Look For

Pull several threads from the yarn of a woven swatch — do not burn the whole swatch. Grip the threads with metal tweezers, hold them over the metal tray, and bring the butane lighter flame slowly to the end of the threads. Observe and record four things:

1. Flame behavior — Does the fiber ignite easily? Does it melt away from the flame or burn toward it?

2. Self-extinguishing behavior — Does it keep burning when you remove the flame, or does it go out?

3. Odor — What does the smoke smell like?

4. Ash or bead — What remains after burning?

Key identifiers by fiber group:

• Cotton and linen (cellulosics): Burn quickly toward the flame, smell like burning paper, leave a soft gray or white ash, and continue to glow after the flame is removed.
• Wool and silk (protein fibers): Burn slowly, self-extinguish when the flame is removed, smell like burning hair or feathers, and leave a crushable dark ash or char.
• Nylon (polyamide): Melts and pulls away from the flame, burns slowly with a celery-like odor, and leaves a hard tan or grayish bead.
• Polyester: Melts and pulls away, burns with black smoke and a slightly sweet chemical odor, and leaves a hard dark bead.
• Acrylic: Burns quickly, may flare, smells acrid or chemical, and leaves a hard irregular bead.
• Acetate: Burns quickly, smells like hot vinegar (acetic acid), and leaves a hard, irregular, dark bead.

Always compare your recorded observations against the DLI burn-test reference chart before writing your fiber ID.

The Acetone Solubility Spot Test: Distinguishing Look-Alikes

Some fibers share similar burn behavior. Acetate and triacetate, for example, both smell like vinegar when burned. The acetone spot test resolves the difference:

1. Place a small cut of the swatch on a white ceramic tile (white shows color change clearly).

2. Apply one drop of acetone from the dropper bottle.

3. Wait 30 seconds, then observe the surface.

4. Record whether the fiber dissolves, softens and distorts, or shows no change.

Key results:

• Acetate dissolves or becomes sticky/distorted — acetone breaks it down.
• Triacetate is resistant to acetone at room temperature — it shows little or no change.
• Nylon is not affected by acetone — no change.

This test works because acetate and triacetate differ in the degree to which the cellulose has been esterified. Regular acetate is soluble in acetone; triacetate is not. The spot test gives you the chemical evidence the burn test alone cannot.

Important: Never use acetone near the open flame used in burn testing. Complete all burn tests, extinguish the ignition source, and then set up the solubility tests in a ventilated area.

Recording and Interpreting Results

Use the structured data table provided. For each coded sample, fill in every column — do not skip odor or ash even if they seem minor. Patterns across multiple columns, not a single observation, give you a confident ID. When two fibers remain ambiguous after the burn test, the spot test column is your tiebreaker. Your completed table is reviewed by your instructor; you must correctly identify at least 9 of 10 coded samples to meet the 85% accuracy standard for this lab.