You know how you rack these up, and up, and up, every time you go to a supermarket or a grocery store? I know you use some as trash can liners, and that's all cool, but what about the extras? DO THIS!!
The Plastic BagBag!
First you turn those loads of plastic bags into handy-dandy plastic bag yarn. This is easy, so give it a go!
Step The First :: You have what's pictured above, yes? An ordinary unsuspecting grocery sack. Flatten it out by holding onto a corner and its corresponding handle, tugging, and repeating on the other side. Pretty much just flatten it out into a more tidy arrangement, as pictured below ::
It's fine and normal to have a lot of extra plastic hanging around inside, as you can see on my sides. That's because of the way the bottom seam is made. Just straighten everything out going one direction :: up and down.
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Step The Second :: Roll the bag tightly, from one side to the other, so that the base is at one end, and the handles at the other, as pictured above. Straighten it out again. This is important for strong bands. Now grab some skissors and make cuts across, about 1 inch apart. Start at then base end, not the handles end. See pictures below.
Continue until you reach the handles.
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Step The Fourth :: Now you have what's pictured above :: A big pile of rolled up cut bits. Unroll one, and you will see it forms a loop.
Test the strength of each loop as shown below. Give it a steady, firm tug, and if it snaps at a weak point, either throw it out, or tie the ends together with a square knot.
Step the Fifth :: Slip on loop over your hand, and let it hang from your wrist, as shown below. Grab another loop with your hand, as pictured.
Thread it over the one on your wrist, and then grab the other end of that wrist-loop. See the picture above. Now it looks like the picture below. One loop is suspended from your wrist and hand, and the other is threaded onto the middle of it.
Now, keeping hold of the end in your hand, slip the loop from your wrist over your hand. Pull the end still in your hand. The two plastic loops are interlocked now. Carefully tighten the junction by pulling both ends.
It will be tight enough when it looks like the picture below.
Continue connecting the loops into a long strand of plastic-bag-yarn. Go as long as you like and then roll it into a ball.
So there you are! You've made your yarn. What you do from this point is up to you. I've made bags using two different methods :: Knitting it up on giant plastic size 16 knitting needles, and then stitching it, OR working a tubular sack up on a knitting loom. In my experience, I could get three rows out of two bags' worth of "yarn."