How to Felt and Sew with Wool Sweaters

What would you say if I suggested there was a textile choice that was water resistant, self-cleaning, temperature regulating – and sustainable and biodegradable?  Sounds a bit like magic, doesn’t it?  It’s not magic – it’s nature!  This versatile fibre is wool, and it has been an integral part of human textile tradition for centuries.

Wool has regained popularity over the recent years for the sustainably minded sewist, and for good reason.  In particular, many are discovering the pleasure of sewing with felted secondhand wool, like the cosy Pathfinder Vest pictured above.  Have you ever wanted to try felting a wool sweater?  Read on, and we'll explain how to do it.  

Why and how does felting occur?

Wool fibres are covered in small “barbs” or “scales”, which allow them to grip to one another, giving an animal’s coat better protection against the cold and wet.   As fibre artists, we can use this property to create a beautiful, dense material that is protective against temperature and moisture, and is durable.

Felting occurs when wool fibres/materials are treated with a combination of factors, which cause the “barbs” on the wool fibre to stand on end, and allow the fibres to interlock.  These factors include:

  • Heat
  • Moisture
  • Agitation
  • Harsh chemicals (like soap)
  • Sudden temperature changes

This process can be done on the cleaned wool fibres themselves, to create what is simply known as “wool felt”, or on finished textiles in which the fibres have been spun into yarn and then knit or woven.

For our crafting and sewing purposes, we will be discussing the felting of finished knitted materials, such as sweaters. 

Simple wool felt (the kind that comes in squares or sheets) is often not an ideal material for sewing garments.  The fibres have not been spun, then knit or woven for additional structure, so they tend to lack the durability necessary for garments.  Felted sweaters, on the other hand, are quite strong - they will shrink considerably, producing a material that is thick, dense, and fuzzy, with less defined stitches or open spots in the weave.  They also won’t unravel, which allows them to be used in all sorts of fun ways.

Choosing a sweater

To create your own felted sweater material, look for secondhand sweaters that have a high wool content – I find 100% wool to be ideal, but have had success felting sweaters with as low as an 80% wool blends for different purposes, especially when I don’t need it to be quite as dense.  While most animal fibres can felt, regular sheep’s wool tends to do so the most thoroughly; you may have luck with others like superfine merino, angora, mohair, cashmere, alpaca, and others, but results can vary.

Ensure that your wool has not been treated to be “superwash” or “washable wool” – this process coats or removes the barbs of the wool so it can no longer felt.  Superwash wool often has a sort of plasticky feel to it.  Look for sweaters which indicate “dry clean only” on the label, to be sure.  

How to felt a sweater

Remember how I said above that wool felts with a mix of heat, moisture, agitation, soap, and sudden temperature changes?  This makes the modern automatic washing machine a perfect environment for felting to happen – a fact you may have run into firsthand, if you’ve ever accidentally washed your favourite woollens and had them emerge small enough to fit your toddler!

For many sweaters, the best place to start is to simply throw it in with your regular laundry.  You can control the level of felting somewhat, by controlling all those factors which cause the wool to felt.  I like to think of felting as continuum – not all or nothing.  You can lightly felt a material, felt it completely, or anything in between.

For instance, if you want to lightly felt a sweater – perhaps make it more dense, but not lose all its stretch – you may start with a “delicate” cycle, with low agitation and consistent water temperature.  Or, for a more complete felting, try a “heavy duty” cycle which uses high agitation and heat, and then a cold rinse.

If, after the first wash, it’s felted to your liking – you’re done!  Just lay flat to dry.

If it has gone through one wash cycle and you'd like it more felted, you can either throw it back in a second time, or consider running it through the dryer, if you use one.  Do this with care though – it can felt your wool very, very quickly!  If I’m aiming for a certain “level” of felting or remaining stretch, I will often check it every 5 or 10 minutes, removing it once it has felted to my liking, laying it flat to complete drying.

Here is an example – from unfelted, to the first wash, to the second wash, you can see how the material is changed.  This can give you a place to start in deciding how to treat your wool, but remember, all wools felt a bit differently.  You will probably have to do some experimenting.

If you don’t use an electric washing machine, you can still felt wool.  Just hand wash vigorously with detergent, or consider methods like “wet felting” which involve wetting the sweater with soapy water and rubbing.

What to expect

There is always a fair amount of chance at play when felting a sweater - different factors like fibre content, weight, knit structure, etc can all play a part in just how much a sweater will felt, and its finished texture.  

Generally speaking, you can expect your sweater to shrink fairly significantly in most cases.  Here’s an example I found while out thrifting - these are both cashmere sweaters, of a similar weight.  By all evidence, both started at around the same size.  Yet the green one must have been inadvertently washed by the previous owner, and was now so small, it had actually been placed into the children’s clothing section!  I find wool and lambswool tend to shrink the most, while cashmere, extra fine merino, and alpaca tend to require more felting to shrink significantly.

You can expect the texture of the sweater to change quite a lot.  It will almost always end up more fuzzy, as the felting process can tease out the ends of those fibres a bit.  The fabric itself will become more dense, and may lose a significant amount of stretch, ending up similar to the texture of boiled wool.  You will see much less stitch definition, and may lose textures that are knit into the fabric like cables, baubles, etc.  Some wools will become quite rough (like lambswool) while others will stay nice and soft when felted (like cashmere).

Sewing with a felted sweater

Once a sweater has been felted, there are all sorts of possibilities for how to use it.  Since the wool will shrink, many prefer to use it for small projects that don't require much fabric, like Wayfarer Shoes, Tie Back Boots, or Pixie Hats.  They work wonderfully for baby and toddler vests, as well.  Felted wool also makes for lovely appliqué, patch, or pocket pieces on bigger wool projects, such as wool Pathfinder Vests or Pixie Coats, since the edges won’t fray, they can be stitched on very simply without having to fuss about covering the edges completely.  It is also easy to piece together for larger pieces as needed.  Perfect for letting your imagination run wild!

Caring for felted wool items

Don’t worry if a sweater is labeled as “dry clean only” – wool items can most certainly be washed at home with some care.  Fortunately, wool doesn’t need to be cleaned very often, as it tends to shed most messes and is naturally odour-resistant.

It’s not quite true to say that your wool is now “machine washable” – while felting it does make it less prone to additional felting, there isn’t always a definite end point to the felting and harsh wash practices carry the risk of shrinking your piece further.  Many wools will do fine with a delicate wash with mild soap after felting, but this is no guarantee.

The best practice is to hand wash in tepid/lukewarm water, with a mild soap like baby shampoo or purpose-made wool wash.  Simply lay them in the water gently and let them soak, avoiding agitation.  You can spot clean harder-to-wash stains by applying some soap directly, and sort of pinching it into the stain with your fingers.  When rinsing, make sure to use water that was the same temperature as your wash bath, and again avoid too much agitation.  I like to pick them up and lay them down repeatedly, to let the rinse water gently flow through.  Then remove as much water as you can by rolling in a towel, and lay flat to dry. (Don’t wring the piece – this can cause your wool to misshape.)

I hope these tips give you the confidence to give felting a go yourself!  We’d love to see your felted wool pieces.  You can tag us @twigandtale on Instagram, or share them in our Twig + Tale Chat group on Facebook.  Participating in the current Upcycle Challenge?  Make sure to tag your project with #TTUpcycleChallenge to enter!

Images by Jocelyn Buggie, Martha Middleton, Angela Schade, Addy de Kam