It is vital that the yarn you choose is 100% wool and that it is not a machine washable yarn. It is possible to get yarn with a small proportion of man-made fibre to felt, but leave that for when you know what you are doing - if you have never felted before, you need 100% wool. If it has been treated to make it machine washable then it will not felt, so read the label and only use yarn that says hand wash. A loosely spun yarn is best, and ideally a chunky one as you won't spend so much time unravelling the individual strands.
To make enough felt balls for a necklace similar to the one in the photo you will need:
about 18m of chunky, 100% wool yarn (or the equivalent weight of a finer yarn)
a small bowl
washing up liquid or other liquid detergent
Step 1: Preparing the Yarn
Separate the strands in each length. The yarn in the photos has 3 strands. Lay them randomly on top of each other, not all aligned.
Step 2: The Felting Process
Boil the kettle and fill a small bowl with water that is just cooler than boiling. Cover your table with old newspaper to soak up any splashes of soapy water.
Scoop up the strands in the palm of your left hand (assuming you're right handed) and squirt on a small amount of washing up liquid. Work it though the pile of strands with the fingers of your right hand.
Now pick up the little heap of soapy yarn with your right hand and dip it partially in the hot water. Remove it and let it cool a little so you don't scald yourself. As soon as you can handle it, put it back in your left palm and work the water through the fibres with the fingertips of your right hand.
Form the bundle of strands into a ball shape and rest it on the closed fingers of your left hand. Use the closed fingers of your right hand to roll it, moving your hands in circles in opposite directions one above the other. You need to try and exert a little pressure with your hands, as it is the combination of moisture, heat and pressure that causes the fibres to felt together. At first it will be impossible to press on the ball at all without it squashing, so just keep rolling lightly. Using the closed fingers of each hand to start with, rather than the palms, will help because the ridges between your fingers provide traction. Don't let the ball of fibres slide between your hands or it will deform and will not felt. If your hands get too slippery and covered in foam, give them a wipe on a cloth.
Dip the ball in hot water again from time to time. I found that 4 dips in total were enough for a ball of 18mm diameter. If it gets too wet it will be very squashy and hard to roll, so roll it on a few sheets of kitchen paper if necessary to absorb excess moisture. Don't be tempted to squeeze the water out of it and then try and reform it into a ball shape, that is likely to result in a ball with a join that hasn't felted together properly.
Keep rolling and applying as much pressure as you can. The ball will get smaller (see photos) and firmer so that you can press harder and harder on it with your hands. The entire process might take 15 minutes for your first attempt, but probably no more than 5 minutes per bead when you know what you are doing. Towards the end of the process, move the ball into the palms of your hands so you can push them together harder - this is easier if you turn your hands vertically rather than one above the other. Alternatively, you may prefer to roll it on the table instead (move the newspaper first) using just one hand, as you can exert more pressure like this. However you do it, keep checking to see that the bead is spherical and coax it gently back into shape if it isn't.
How do you know when you are finished? When the ball feels really quite hard, it's not getting smaller any more, and when you give it a squeeze between thumb and forefinger, it springs back into shape. Rinse it thoroughly under the cold tap and then put it down on the newspaper until it has stopped dripping. Leave it on a sunny windowcill or on a radiator to dry for 24 hours or so.
Step 3: Making the Remaining Beads and Stringing Them
The necklace shown in the picture has 13 beads in the following sizes:
length of yarn size of bead number of beads
1m 15mm 4
0.6m 12mm 4
When they have all dried, string them using a needle and thread. I used tiger tail, threading it through a needle with a reasonably large eye. You can mix them with any other beads you may have - I used some small rock crystal ones.
If anyone is interested, I can do another I'ble showing how to attach a clasp, etc.