“What,” you’re thinking, “is plarn?”

If you’re a crafter or recycler, you might know what “plarn” is. If not, here’s a definition:

Plarn is a creative way to recycle plastic bags by turning it into yarn. Plastic bags made into yarn = plarn. Green crafter’s have been using plarn in place of traditional yarn to crochet and knit all sorts of items.

I started experimenting with plarn last summer,when I improvised a crocheted tote bag for groceries.

The bag was easy to make; making the plarn with which to make a bag, however easy, is tedious and time-consuming — a good thing with which to occupy your hands while watching television so that you keep your hands out of the potato chip bag.

Now, switching to the “brain training” part of this post.

In a recent post at Time Goes By, “Our Plastic Brains — Even in Old Age,” Ronni Bennett reports:

Earlier this month, The New York Times published an essay from Dr.[Oliver] Sacks about how our brains are almost miraculous in their ability to stretch, adapt, overcome injury, retrain themselves and perform feats we could not imagine before.

In addition to giving me an excuse for talking to myself, the TGB post got me thinking about the brain benefits of learning to make and combine knitted geometric shapes.. I could have used regular yarn, but using up our plastic bags gave me a practical point to my creative math exercises.

I started off trying to separate my plastic bags by color. I had a lot of red and white bags from Target, CVS, and Macy’s, so that’s what I started with. Using instructions from a wonderfully simple book, “No-Pattern Knits” (which I bought used cheap from Amazon.com), I made one right triangle, and then added another triangle to make a square (which is one side of the tote bag).

You can see from the photo that the knitted ridges go one way on one triangle and another way on the second triangle. That’s where the Pythagorean Theorum has to be used as well as some algebra to figure out number of stitches for xxx number of inches. I did the second triangle wrong the first time and had to rip it out and figure it out all over again — finally correctly. To make the square into a rectangle, I knitted extra rows on each side of the square.

I was never terribly good at — or interested in — math, and spatial relations was the part of the IQ test I always did the worst at. But combining my passion for knitting with a necessity to use math skills has become a fun way to keep training my brain.

For the second side, I wanted an asymmetrical look, so I used up some bags of other colors and made a mitered square that I positioned as a diamond — with other triangles knitted off the edges to form a large square. Then I added on to one side of the square to make an rectangle.

I made the tote/purse a size in which I could fit a purse organizer that I had purchased a while ago that was too big for the purses I already own. I attached the purse organizer to the inside of the plarn puse with sticky-back velcro.

Plarn is tricky to work with in some ways. The strips can stretch and break as you work, and if you sew it with regular thread, the thread can cut through the plastic. So whenever the plarn purse’s construction required me to sew something, I sewed with a strip of plarn and a yarn needle.

I have every intention of actually using this plarn purse. If nothing else, it’s a conversation piece.

If I ever make another one, I’m going to spend some time coordinating and combining the plastic strips to vary the colors. It’s all a learning process. Good for my brain.