Felting Old Wool Sweaters Into Fabric You Can Sew

The charity shop near me sells jumpers for $4 each, and the moth nibbled ones end up in a bin by the till for a dollar. That bin is the best fabric supplier I have ever found. One hot wash turns a stretched, holey wool sweater into a dense, soft felt that you can cut with scissors and sew without a single hem, because the edges simply do not fray.

Felting old wool sweaters is one of the easiest upcycling projects for someone who can sew a straight line and not much else. It is also one of the easiest to get wrong if you pick the wrong sweater. Most failures I see come from the label, not the washing machine. Here is how I choose, shrink and use them, including the steps the cheerful online tutorials tend to skip.

Which Sweaters Will Actually Felt

Felting happens when animal fibres with tiny scales on their surface are agitated in hot, soapy water. The scales lock together and the knit shrinks into a solid mat. Plant fibres and synthetics have no scales, so they will not felt at all.

Read the care label before you pay. My rule of thumb:

100 percent wool, lambswool, merino or Shetland: felts well, the safest choice.
Alpaca, mohair, angora or cashmere: felts, often faster, but can become thin or fuzzy.
80 percent wool with nylon: usually felts, a little less dense.
Anything under 70 percent wool, acrylic, cotton or viscose: skip it.
Labelled superwash or machine washable: skip it. These are treated so the scales cannot lock, which is the whole point.

Thicker knits give thicker felt. A chunky Aran knit makes felt sturdy enough for a bag base. A fine merino makes something closer to a soft flannel.

How to Felt Old Wool Sweaters in a Washing Machine

You do not need special equipment. You need heat, agitation and a little detergent.

Cut off any labels and remove buttons or zips.
Put each sweater in a zipped pillowcase or mesh laundry bag. Felting sheds a surprising amount of fluff, and it can block a pump filter.
Add an old pair of jeans or two tennis balls for extra friction.
Wash at 60 degrees Celsius, or 140 Fahrenheit, on the longest cycle with a small amount of ordinary detergent.
Check the result. If you can still see clear stitches, wash again.
Pull the piece flat by hand while damp and air dry it, or tumble dry on medium for a final bit of shrinkage.

Expect the sweater to shrink by 20 to 40 percent. One that fitted an adult may end up the size of a child's top, which is exactly what you want.

Sorting Colours and Avoiding Surprises

Hot water releases dye. Red and navy wool are the usual culprits. Wash darks and lights in separate loads the first time, and never put a felting load in with ordinary laundry.

Stripes and Fair Isle patterns can felt unevenly, because different yarns shrink at different rates. Sometimes this gives a lovely puckered texture. Sometimes it gives a warped panel that will not lie flat. Treat patterned sweaters as an experiment, and save your plain ones for projects where size matters.

The Advice I Disagree With

Plenty of tutorials say a hot tumble dry alone will felt a sweater. In my experience it rarely does more than shrink it slightly and leave it misshapen. Without water and agitation, the fibres do not interlock properly, and you get a small sweater instead of real felt. The washing machine does the work. The dryer just finishes it.

The other advice I would ignore is to save cashmere for the best projects. Cashmere felts quickly but turns soft and thin, and it pills with use. For anything that gets handled daily, like a phone case or mittens, an ordinary lambswool jumper makes more durable felt.

Projects That Make the Most of Felted Wool

Project	Sweaters needed	Best part of the sweater
Set of six coasters	One	Body panel
Mittens lined with fleece	One	Sleeves and ribbed cuffs
Cushion cover	One or two	Front and back panels
Tote bag	Two or three thick ones	Body for sides, scraps for handles
Small pet bed	Three or four	Patchwork of panels

The ribbed hem and cuffs keep their stretch even after felting, so I cut them off and use them as ready made edges for hats and mitten tops. Sleeves are already tubes, which makes them perfect for phone sleeves or bottle covers.

Cutting and Sewing Felted Knits

Felt does not unravel, so you can cut shapes directly and butt the edges together. A simple blanket stitch in a contrasting wool yarn looks deliberate and handmade. On a sewing machine, use a size 90 or 100 needle, a longer stitch around 3.5 mm and a walking foot if you have one, since thick felt tends to creep. Our guide to choosing the right needle and thread weight explains why the heavier needle matters.

Keep every offcut. Pieces as small as your thumb work for appliqué, and I sort them by colour in a shoebox. If you are short on space, our article on which fabric scraps are worth saving will help you decide what earns a place.

Caring for Finished Felt Pieces

Once felted, wool cannot shrink much further, but it can still change. A coaster or cushion cover that goes back into a hot wash will tighten a little more and may warp. I hand wash finished pieces in cool water with a wool detergent, press out the water in a towel and dry them flat.

Moths are the real enemy. The same larvae that made holes in the original sweater love felt just as much. Store spare felt in sealed plastic tubs with a few cedar blocks, and give the stash a shake and a look every couple of months. A single infested sweater from a shop bin can spread to everything else, so I freeze new finds for 72 hours before they join the pile.

Frequently Asked Questions

Can I felt a sweater by hand instead of in a machine?

Yes. Use a bucket of very hot water and a second bucket of cold, plus soap and rubber gloves. Knead and plunge the sweater between them for 15 to 30 minutes. It is slower but gives you more control.

Will moth holes close up during felting?

Small holes often close completely, because the surrounding fibres shrink and lock together. Larger holes shrink but remain, so plan your cutting around them.

Can I felt a sweater that is still wearable?

You can, but I would not. Wearable wool sweaters are better passed on to someone who will wear them. Felting works best on the ones that are past saving as clothes.

Your First Felting Load

Buy two plain sweaters labelled at least 80 percent wool and not superwash, bag them, wash them at 60 degrees with a pair of jeans, and check the stitches before a second wash. Start with a set of coasters from the body panel and blanket stitch the edges. Once you see how forgiving felt is, the dollar bin will never look the same. More ideas live in our upcycling section.