How do you felt a woollen jumper/sweater? This question often lands in my inbox and while I know there are a few different methods out there, here is the one that I use.
To start with you need to hunt down your woollen garments for felting. Whenever I visit an op-shop, this is the first thing I search for. I still haven't quite figured out how to spot a pure woollen garment, so I spend a lot of time reading the tags inside the clothing to see if they're acrylic or wool. I only buy clothes to felt that say 100% pure wool now, but I have felted a few that have had a touch of acrylic mixed in with the wool in the past and they've turned out okay.
The first step is to cut up the clothing and remove all the seams and tags. Initially I would just felt the entire garment and cut it up later, but now I prefer to cut first and then felt. It's just a matter of personal preference I guess.
Pop the cut up garment in your washing machine and add a generous squirt of dish washing detergent. Ensure the wash cycle is on 'hot' and start washing :) I usually stop my washing machine once it hits the *spin* cycle, but sometimes I forget to do this. After the first wash, have a look at the garment - usually on my first wash the garment has barely felted, so I just pop it back in for a second go, following the same process.
Sometimes I've had to go through the cycle about 4 times before I'm happy with the felting, other times it has only taken 2 washes. I also try to keep my colours together when felting - just to ensure that dye doesn't leak out from one and into the other garment.
Once the garment has felted, I just pop it on the clothes line to dry and then fold it up in the cupboard so it's ready to go when a project pops into my head. You can sew the sweetest softies using felted jumpers and once you've felted your first garment, you'll realise that it's highly addictive and super easy.