I found these handy instructions quite a while ago and merrily collected bags. Chopping and joining I eventually had enough bags to make this:
I personally love the irony of taking 40 perfectly functioning carrier bags and turning them into one perfectly functioning bag. Somehow I think it's the opposite of what a capitalist society says you are meant to achieve. This bag is made from Morrisons carrier bags, it's probably about 12 inches square when laid flat. I crocheted it using treble crochet and in the typical fashion I followed no pattern making it up as I went along. Sadly I didn't write the pattern down.
You may be thinking of doing something like this so let me give you some advice.
1. Choose the crappiest quality bags you can get your hands on, ones that will stretch if you pull on the plastic with small force. I tried to use thick carrier bags on another bag I made and paid the price, for three days I could barely move my fingers.
2.You need an awful lot of bags to make one bag (there's a sentence that doesn't make sense in isolation!) if you ask people for plastic bags they will give you them. Lots of them. And they will keep giving you them until you scream "PLEASE NO MORE!!" My car boot is currently full of plastic bags that I have no room for in my house, they need to be chopped up joined and rolled up before I can even begin to use them.
3. I would like to refer back to the last sentence of number 2 "they need to be chopped up joined and rolled up before I can even begin to use them" recycling bags is an arduous task. It takes an age before you can begin to start using your plastic bag yarn. If you really want to do it then have a go, but it will help to have a small army of people willing to chop up, join and roll.
Plastic bag yarn is fun, it makes an interest talking point and it's very 'in fashion' what with all the talk of recycling. Another design I used is fun as well as practical, you can use this to play a Guess The Shop game which can provide up to 12 minutes of clean wholesome family fun.