Demystifying Mystery Yarn: WPI and Fibre Content

Demystifying Mystery Yarn_ WPI and Fibre Content.png

When I first told people I was learning to knit, I suddenly found myself inundated with more balls of donated mystery yarn than I could shake a knitting needle at.

I grew up with my Grandparents, so a lot of our family friends were elderly ladies. They were all very excited at the idea of a young 'un taking up knitting, and were incredibly eager to help.

If you've taken the free From Newbie to Knitting Know-It-All course, you will have learned that cheap yarn isn't necessarily a bad thing. FREE yarn is even better when you're just starting out.

That being said, unidentifiable balls of miscellaneous yarn can pose some problems.

Knitting patterns are often pretty particular in the yarn they recommend. They usually provide a very specific yarn from a very specific brand. Although you don't need to use the same yarn the pattern suggests, the weight/thickness of yarn is very important; especially if you're a beginner.

Your pattern states that you need a double knit yarn. You're planning a baby blanket so you want it to be acrylic so it's easily washable.

How are you supposed to know what on earth your yarn is when it was all donated by Margaret next door? First, you want to find out the weight of your mystery yarn.

That's where calculating the WPI comes in, or Wraps Per Inch.


So, after calculating the WPI and establishing that you have a DK yarn in your sweaty little palms, you need to decipher what the fibre content is.

“How the heck do I work that out?!” I hear you cry!

You set fire to it. YAY! Whut?!

Did you know that every fibre group (animal, plant, synthetic) burns differently?

To be honest, this probably isn't a revelation to you, most people know that burnt hair smells foul, plants turn to ash and crumble, and plastic melts and smells fairly acrid and toxic.

Using these simple observations, we can actually work out the fibre content in a yarn.

Now, this is a not an exact science, there are hundreds upon thousands of yarns, and probably just as many different fibre blends! For example, a pretty common sock yarn blend would be 80% wool, 20% nylon AKA 80% animal, 20% synthetic. But for the most part, if a yarn reacts a certain way, we can figure out the majority of the fibre content.

So, how does each burn?

Animal Fibre

Examples: wool, alpaca, merino, angora (this is not the same as fur, the animal is sheared which is actually very beneficial to the animal)

It doesn't really take flame, it turns to ash, and it smells like Satan's under-crackers.

Plant Fibre

Examples: bamboo, cotton

It burns like paper with very little ash and smells quite nice.

Synthetic Fibre

Examples: acrylic, nylon, polyester

Melts into plastic and smells toxic in large quantities (probably because it is toxic).

So now we know that we have an acrylic DK yarn. Now get started on that baby blanket!

If it's going to be a gift, I suggest knitting a swatch and throwing it in the washing machine and dryer to see how it reacts. Then you can give the new recipient washing instructions so they don't accidentally melt it - new mums are stressed enough!

Do you have any mystery yarn in your stash that you're going to use these techniques with? Let me know!

Related Post: Knitting Needles: A Beginner's Guide