By My Own Hand

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Burn testing fabrics and threads for fiber content

First, a few words about safety:

1. Do this only in a a well ventilated area (open some windows or do this outside in a relatively still, not windy area..).
2. Do not actively inhale smoke.
3. Do not hold flaming things in your bare hands. This can be painful!
4. Have a fire extingusher on hand, just to be safe.
5. Don't use matches. Use a disposable lighter (not a Zippo) for both safety and clarity of fiber "smell".

Next, a disclaimer:

You will not be able to determine which type of animal (protein) or vegetable (cellulostic) fiber you are dealing with by using a burn test. Burn testing is predominantly used to determine whether one is dealing with a synthetic substitute for animal or vegetable fiber, or a silk substitute (rayon is a vegetable fiber). Some persons claim to have been able to detect differences through long experience (for example, telling the difference between silk and other animal fibers), but this is unusual.

Blends also will be difficult to determine, although it is possible to determine that you have a blend, and whether it is mostly synthetic or natural, by noting all the behaviours of the swatch in response to burning. Practice will increase your skill. Warp and weft fibres are tested seperately because they are often different in blended fabrics.

Advice:

• Prewash your fabric (at least your test swatch) before you test it. Finishes can confuse your results.
• Don't test while your nose is stuffed up. You won't be able to get a clear idea of fiber type.

Materials and equipment to use

This includes materials for a swatch notebook, so you won't need to repeatedly test one fabric you have on hand if you don't use it right away.

• 2 small (2"x2") swatches of each fabric you are testing
• if you are testing yarn or thread, have 2 lengths approximately 4" for yarn and 10" for thread of each yarn or thread that you want to test.
• a notebook (the half-size spiral-bound ones work well for this) and pen
• a small piece of cardboard (the back of a scratchpad will do)
• double faced tape or white glue
• a pair of needlenose pliers (jeweler's or hobbyist's pliers work well for this)
• a disposable lighter and nonscented paraffin candle
• a bowl of water and a dish of baking soda (mini fire extinguishers, use only if needed)
• foil or a large cookie sheet as a working surface

Step-by-step instructions

1. Test swatch and notebook preperation: Tape or glue one of each swatch (these are for reference) into the notebook, giving yourself about half a page for notes on each swatch. I usually put them on the right hand page, leaving the left hand page blank. Place the cardboard under the first sheet when you are done so you don't have trouble writing. Fringe out about 3/4" on two edges of each test swatch, one on the warp, one on the weft (warp is lengthwise in the fabric, weft is widthwise). If testing yarn/thread, bundle the yarn/thread swatch up into a 2" length when ready to test it.
   
   
2. Work area preparation: Lay out the foil or cookie sheet, and set the small bowl of water and the dish of baking soda within easy reach. Put the candle in the middle of the foil/cookie sheet. Light your candle and let it burn for a few minutes. Make sure you are working in a well-ventilated area (but not windy - wind and fire don't mix!). Have the pliers and lighter handy. Lay out your notebook and pen.
   
   These instructions are for individual fabric swatches from here on (for yarn/thread, simple follow these instructions but omit the 6th step):
   
   
3. Take a swatch and grip it firmly in the pliers. You may want to secure the plier grips with a rubber band.
   
   
4. Hold the fringe of one edge near the flame. Note its behaviour. Does it melt? Does it smoulder?
   
   
5. Move the fringe into the flame, then away from the flame. Blow it out if necessary. Note its behaviour. Does it melt? Does it put itself out? How does it smell? Does it form a bead? Does it leave ash? Does it produce a distinctive smoke?
   
   
6. Repeat with the other fringed edge.
   
   
7. Note all behavours in your notebook, then check the reference list below for a diagnosis. Tape or glue the burnt swatch into the notebook with the reference swatch, so you know what it looks like when burnt.

Typical Burn Behaviors of various fibres:

Vegetable fibres (cotton, rayon, linen, hemp, ramie, jute, etc)

• Burns or melts? only burns
• Retreats from flame? no
• Smell? Burning paper, leaves, wood
• Residue? fine grey ash
• Misc? Glows before going out

Animal fibres (wool, mohair, cashmere, alpaca, silk, rabbit, etc)

• Burns or melts? only burns
• Retreats from flame? yes
• Smell? Burning hair,feathers or meat (silk does not have as strong an odor as the other animal fibres)
• Residue? dull black hollow bead which crushes easily to grit
• Misc? self-extingushing

Synthetic fibres -each has its own behaviour listed below

Acetate

• Burns or melts? melts&burns
• Retreats from flame? yes
• Smell? Burning paper&vinegar
• Residue? dark hard bead
• Misc?

Acrylic

• Burns or melts? melts&burns
• Retreats from flame? yes
• Smell? Burnt fish or acrid
• Residue? hard lumpy black bead
• Misc? black smoke, sputters while on fire

Modacrylic

• Burns or melts? melts&burns
• Retreats from flame? yes
• Smell? chemical
• Residue? hard black bead
• Misc? puts itself out

Nylon

• Burns or melts? melts&burns
• Retreats from flame? yes
• Smell? celery or vegetable smell
• Residue? hard cream-and-coffee color bead
• Misc? flames come from finish, drops of melted nylon may fall from swatch

Olefin

• Burns or melts? melts&burns
• Retreats from flame? yes
• Smell? chemical or paraffin smell
• Residue? hard light to medium brownish bead
• Misc? black smoke

Polyester

• Burns or melts? melts&burns
• Retreats from flame? yes
• Smell? icky sweet chemical smell
• Residue? hard creamy color bead, may be dark if burnt for awhile
• Misc? black smoke, melting polyester drips

Spandex

• Burns or melts? melts&burns
• Retreats from flame? no
• Smell? chemical, burnt rubber smell
• Residue? black ash
• Misc?

If it doesn't catch fire at all it is probably glass, aramid or novoloid (these last two are industrial flame proof fabrics).

Subtypes of fibres, synthetic or natural usually behave like the primary fiber (various types of acetates will behave like acetate, all types of rayon behave like rayon). I didn't list some types of fibre which you are unlikely to encounter in fabric, like vinyon (used for fishing nets) and saran (mostly used for industrial stuff and doll hair).

Sources

All information used in this came from practical experience, the knowlege my mother passed on to me and my textile science course - teacher and textbook . An excellent reference is Pizzuto's Fabric Science by Price/Cohen, Published by Fairchild Publications. Mine is the Sixth ed, and and may actually be out of date by now.