Sometimes we need to know the exact fabric content of something we are planning to use. I’ve always done a rudimentary burn test but sometimes it is hard to know from that anything other than it is a natural fiber. When dyeing fibers, you need to know if it is cotton, silk, wool, rayon or something else because of mordants used.

 

I found a wonderful chart at http://nvg.org.au/.  The New Varangian Guard Inc. (NVG Inc) is a historical re-enactment organization with branches throughout Australia, and sister organizations in several other countries.  I am copying the chart below and giving them credit since the original source of the information is a dead link.

 

How to tell what the fiber is:
Burn Test
Snip a piece of fabric equivalent to 1″ square. Using butane lighter and holding the fabric with a pair of tweezers ignite the fabric over a non-flammable surface in a well ventilated area.

Examine the quality and color of the flame, the odor produced, and the quality of the resulting ash or cinder.

Use this table to help determine your fabric’s content.

FABRIC	FLAME QUALITY	ODOR	ASH QUALITY	COMMMENTS
WOOL	orange color, sputtery	burning hair or feathers	blackish, turns to powder when crushed	flame will self-extinguish if flame source is removed, no smoke
SILK	burns slowly	burning hair or feathers	grayish, turns to powder when crushed	burns more easily than wool but will self extinguish is flame source removed
COTTON	yellow to orange color, steady flame	burning paper or leaves	grayish, fluffy	slow burning ember
LINEN	yellow to orange color, steady flame	burning paper or leaves	grayish, fluffy	takes longer to ignite than cotton, but otherwise very similar
RAYON	fast orange flame	burning paper or leaves	almost no ash	will continue to burn after flame source removed
POLYESTER	orange flame, sputtery	sweet or fruity smell	hard shiny black bead	black smoke
ACETATE	burns and melts, sizzly	acidic or vinegary	hard black bead	will continue to burn after flame source removed
NYLON	burns slowly and melts, bluse base and orange tip, no smoke	burning celery	hard grayish or brownish bead	will self extinguish if flame source removed
ACRYLIC	burns and melts, white-orange tip, no smoke	acrid	black hard crust	will continue to burn after flame source removed

 

Bleach Test:
To determine content of fabrics I recommend conducting this first with fabrics that you are sure about the content of – so you will know the outcome of the test yourself. In a non reactive pan (I use a pyrex pie plate) take snips (small pieces) of the fabric you will be testing. Use straight bleach and put about ½” of bleach in the pan. Please do this in a ventilated area. Add the snippets of fabric and let them sit for about 24 hours. The next day, look at what you have left.

100% Linen or Cotton	any color should be removed from the fabric, but there will be no damage to the fibers themselves
100% Silk or Wool	the fabric will have fully dissolved (unless its worsted/gabardine, there is a fabric treatment that protects the fabric from the bleach and keeps the fabric shiny even after washes).
100% Polyester, Rayon, Acetate, or Nylon	the fabric will have become a cloudy mess within the bleach. Fully dissolved into an opaque cloud within the bleach.
Blends –	The individual fibers will act as described above. The result will be different for each combination
Rayon / Linen	linen fibers with a opaque cloud;
Silk / Polyester and Wool / nylon	fully dissolved with an opaque cloud;
Linen / Cotton	no damage to the fibers;
Silk / Wool	fully dissolved.