Burn Baby Burn - The Smoky Side of Fibre Identification

Hi all.

How's the stash?  Is it full of wonderful pieces of fabric that all came from places where the bolts were labelled?  And when you got home, did you write down all the information from the bolt on a card, and attach it to the fabric before you put it away?

Or is it like mine?  Are there some fabrics that felt really good in the store, and when you looked at the label on the bolt end they were labelled "100% unknown fibres" ( I love that) and you bought it anyway?  Do you have others that you inherited from friends and relatives and you're just not sure what they are?  Do you buy fabric from thrift stores?  Wonder what to do with them when you get home? 

Have no fear!  You are here!  Help is on the way!

 A burn test will help you identify the primary fibre in a given fabric, but it won't help you determine percentages of fibre.  It will help you figure out how to treat a fabric that you are unsure of.  It takes most of your senses - touch, smell, sight.  Plus you get to burn stuff in a safe way.  It appeals to the junior scientist/pyromaniac in me.  But that might just be me. 

First you need to gather a few supplies:

  1. A flameproof vessel - This can be a plate, a cookie sheet or an old frying pan.  It just has to be something that won't be damaged by heat. 
  2. Some tinfoil - I like to do the actual burn test over some foil since molten polyester can be hard to remove from dishes.  Just sayin'.
  3. A vent or an open window - Some of the fibres you will be testing can smell nasty.  Best to send those stinky fumes somewhere else. 
  4. A source of flame - This can be a lighter or some matches.  Personally I like a barbeque lighter because it keeps your hands away from the hot stuff. 
  5. A small bucket of water or other water source - In case things need extinguishing.  
  6. A small sample of the fabric you are curious about - Usually a 1" square will do.

Here's my set-up:

Fancy, no?  A sink is off to the right.  That's a bread and butter plate covered in foil, and a barbeque lighter.  The only thing missing is a vent hood, which we sacrificed for the sake of light and picture taking.  Turned out to be a mistake.  More on that later. 

So now what? 

Well, you burn it.  And you pay attention.  Here's the science behind it:

Every fibre is made up of something different and those differences are unique.  Wool is an animal product.  When you burn it, it smells like burning hair.  It is also self-extinguishing.  That means that while it will smoulder, it won't support a flame for long.  Cotton, on the other hand, will burn like you wouldn't believe.  That's why children's sleepwear has to be specially treated.  Once you have burned your sample, you will have ash and detritus left behind.  Once it has cooled, you can inspect it to see what it can tell you.  Polyester leaves a hard bead behind, while silk behaves completely differently.  I have included a chart that will help you decipher what you have. 

The fabric that I'm burning for this example was purchased at a thrift store.  It looks and feels like wool.  But I'm a little suspicious.  So it's time to put some flame to it. 

It was hesitant to start burning.

But once it got going, it was burn city. 



It smelled like burning hair - very strongly.  This is the part where I wished we had chosen less light and more ventilation because it really stunk up the joint.  Burning hair smell is usually a sign of wool.

The ash that was left over was hard, and very crispy.

When I tried to  squish it, it broke apart into shards. 

So what does all this mean?  Well, according to the chart below, I think I have a wool/acrylic blend on my hands.  That means that it can probably weather a trip through the washer on cold and tumble dry low without much damage.  It might shrink a bit from the wool content, but the behaviour of the flame (full on burning until it was a molten pile of plastic) leads me to believe that there's a lot of acrylic. 

Now I know!

Below I have provided a chart with the burning behaviour of the most common fibres:

Kinda cool, huh? 

This is one of the things that I love about sewing - there's so much to learn. 

Next week:  OEKO-TEX certification - what does that mean, anyway?