You will also need:

• a couple of tablespoons of laundry detergent
• access to a washing machine (preferably top loading)
• something to block your hat on that is the same circumference as you want your finished hat to be.

You don't need to invest in an expensive hat block. You can use many different things, a round plastic vase, an upside round measuring jug, a cake tin, anything that is the right size, fairly firm, and can be left damp.

You can see my hat block on the left, which is an 18cm diameter soufflé dish rested on top of a pot of Nappy San laundry detergent.

Felting Your Hat

There are three things that you need for successful felting of knitted items. Heat, agitation and an alkaline environment. That might sound very complicated, but it isn't really! What it means is this: hot water, a washing machine with a low water setting or an old pair of jeans (or other non-fluffy item that won't bleed dye in the wash), and laundry soap or detergent (the kind without fancy softeners). If you've used a single ply or fluffy yarn you'll also need an old pillowcase or lingerie bag to stop loose fuzz getting into the workings of your washing machine.

Take your hat and put it inside the pillow case or lingerie bag (if needed).

Fill your washing machine with just enough hot water to cover your hat. If you can't change the level of water in your washing machine, add an old pair of jeans for extra agitation.

Put your hat in and let it soak for 10 - 30 minutes. This will give time for all the fibres to soak up plenty of water. Now start the machine. Stop the machine and check your hat after 10 minutes. If it hasn't shrunk enough, keep checking every 5 - 10 minutes until it's the desired size (measure it or try it on!).

Rinse out the soap in water the same temperature as your wash water, or if it's still a little bit too big, rinse it under cold water. The shock of the change in temperature will shrink it a bit more.

Empty your washing machine, spin the excess water out of your hat (don't leave it spinning for too long or you'll make creases that you won't be able to get out).

You'll now have something that looks like this

Blocking

While it's still wet, pull your bell-shaped piece of knitting down over your block until the top of the hat is stretched flat. Turn up the brim and adjust it until it's even all the way round.

Leave your hat on the block to dry.

When you block your hat quite a magical transformation takes place. The felting process shrinks all the stitches in size, and blocking pushes them back into the shape that you knit.