How to make shopping bags into durable plastic sheets and other
articles
This is the first in a series of illustrated In the Wake
how-tos, and also the first in a series on DIY
recycling; how to take items to would get currently thrown
away and make them into something useful in a collapse context.
This
page tipped me off to the fact that you can iron multiple
sheets of shopping bag plastic together to make a thicker, more
durable sheet. I decided to try it immediately to see what was
possible.
Essential Materials: Shopping bags, an iron,
several sheets of paper
Helpful Materials: Needle and thread, or a sewing
machine
Time: Ten minutes (up to several hours for a
very large project)
Skills: Use an iron (optional extras: use a
sewing machine)
(Click here to continue. The how-to contains a large number
of images.)
I plugged in the iron and found a plastic bag in the kitchen.
A quick look at the bottom showed that it was made out of HPDE,
or high
density polyethylene, which is what most plastic bags and
tupperware containers are made out of:
I cut all the seams of the bag to make a single
layer of plastic sheet:
I decided to try to make a simple "two-ply" layer first,
so I folded over the edge of the sheet.
My iron offered a variety of possible temperatures. I didn't
know which one to pick, so I just chose the very middle, between
three and four, which is between "polyester / rayon"
and "blends of cotton."
I didn't want the heat to melt the plastic onto the iron and
ruin it, so I put the plastic between two regular sheets of paper.
And I don't have an ironing board, so I just put the paper and
plastic on top of a thick magazine on the floor, and ironed it
for a few seconds, moving the iron around to heat evenly:
I took the iron off and immediately removed the
top sheet of paper. I could hear a crackling sound as the plastic
shrunk into itself, like rice krispies. The heat hadn't been on
long enough, or the iron hadn't fully heated up, meaning that
the two plastic layers hadn't bonded to each other. So when I
removed the plastic, they contracted and wrinkled up, as you can
see:
I decided to iron for a bit longer and that in the future I would
give it a few seconds to cool before removing the warm paper,
which would stick very slightly to the plastic and help keep it
in place.
I gave it another iron session for slightly longer and then gave
it a few seconds to cool. When I removed the plastic, I found
that the image had also been melted onto the paper underneath
but that the rest of the plastic hadn't stuck. The ink / coloured
plastic got warm enough that it actually looked liquid, and gleaming:
The two plastic layers had melted together, producing a textured
plastic membrane that felt like a cross between Tyvek
(which is also made out of polyethylene) and waxed paper. I rubbed
it between my fingers to try to get it apart, but the two layers
were permanently attached.
I decided to try to make a thicker, three-ply membrane, so I
folded the plastic again, on to an unmelted area, and the ironed
it. The newest layer on the "three ply" attempt didn't stick as
well as the first two had, it looked like it might peel away,
so I flipped it over and ironed the "new" side. This time the
new side stuck quite well, and didn't look like it was would peel
away. The join was quite solid:
The part of the three layered area furthest from me was still
unjoined because I hadn't bothered to iron it. I decided to iron
it for about ten seconds, and it joined perfectly. In fact, it
joined even better than the first one, with fewer wrinkles! I
think this was partly because I left the paper on for a few seconds
as it cooled, and possibly because the iron was slightly warmer
-- further experimentation will answer that.
I decided to try to join eight layers all at once. I folded a
fresh section of the the bag over itself to make eight layers.
I ironed it again for about ten seconds, and then gave it five
seconds to cool. The ironed side worked well, but the last outer
sheet on the "cool" side hadn't stuck uniformly. I gave it another
ten seconds of heat, and then a few more to cool. This time it
stuck perfectly.
I decided to see if this material would still hold together if
I cut it through the middle, so I cut the first (three-ply) experimental
section in half. It was completely indistinguishable from a single,
thicker layer of plastic.
At first I was wondering if I could sew the cut section back
together -- how well would it hold thread? But then I realized
I cold just heat-weld it back into one piece. I overlapped the
pieces slightly gave them about five seconds per side, which worked
perfectly.
I turned my attention back to the eight-ply piece. It cut with
the scissors easily -- but when I tried to physically stretch
it with my hands, I was unable to. It was surprisingly tough.
However, I could rip it, rather raggedly and with a bit of difficulty,
by starting from one edge.
I decided to take it to the sewing machine. I knew I could sew
it by hand. That would be pretty easy and straightforward. But
I wanted to see if I could make a garment in the same amount of
time that it would take to save the the money from a wage job
and buy an equivalent garment in the store.
I set up the sewing machine for the simplest straight
stitch, and lined it up.
Trouble. The stitches didn't go in properly.
I double-checked the bobbin (the little spool of
thread underneath the metal panel) and everything was fine with
it. I remembered that my partner and I had a similar problem a
few years ago when we made our own dry-sacks for a biking trip
out of plastic tarp. The thread tension (which you can adjust
on sewing machines) was too much, and it was pulling the thread
back up and out of the plastic before it could catch and make
a stitch. This seems to be a problem with sewing plastic in general.
One of the downsides of the plastic versus regular
fabric like cotton is that the fabric could be stitched and restitched
without changing appearance. But my failed first attempt left
a row of tiny holes:
I didn't really want the holes. They looked bad, and if I was
trying to make something water-proof a bunch of holes just wouldn't
do. I decided to take it back to the iron and see if I could seal
them up just by melting them shut with another ironing session.
I ironed it briefly, and the holes got a bit smaller. I decided
to iron it for a long time, and then the holes on one side actually
ended up getting bigger again -- probably because of
the shrivelling effect that seems to happen when the temperature
gets too high. So I just cut a strip off of the three-ply peice,
and ironed it on to patch over the holes. That worked perfectly.
Back to the sewing machine. I adjusted the thread tension to the
lowest possible setting, and tried again:
Argh! A different problem this time, the thread
in the bobbin got tangled, so I had to take it out and put it
back in. I tried again, and it worked perfectly to produce a small
pouch:
I wanted to turn it inside out to hide the seams, but this first
experimental pocket was too small and narrow. So I tried a new
bag. I cut the bottom corner seams and pulled them out, and then
cut the handles off to make a rectangle:
Then I folded the two-layer rectancle into quarters
to make another eight-ply piece:
I ironed it for ten seconds on each side. I must
not have done it evenly, because the part furthest away from me
wasn't complete, so I gave it a bit more time with the iron. That
solved the problem.
This design came away onto the paper really cleanly.
Ironing the designs from plastic bag onto paper could be a neat
arts/crafts project in-and-of itself:
I took the new eight-ply piece straight to the sewing
machine, and had no trouble at all now that the thread tension
was adjusted properly:
I just folded it at the long edge, so I didn't actually
need to sew it there. However, I wanted to see how it would affect
my ability to turn the pocket inside out to hide the seams if
I were sewing two completely separate pieces together. Since the
pocket was so large and wide I had no trouble:
A quick creasing along the seams can flattened the
pouch a bit more.
And here are the two pockets along with their source
material:
When I have time a bit later I may put velcro, a
clasp, or some other closure on them to make them more useful
for holding things.
Final notes:
Overall, I was surprised by how incredibly easy it was
to actually do this. It worked pretty much right away. It would
be very easy to expand the scale of the process, and to make it
much more rapid once you have the initial bugs worked out for
your iron and sewing machine.
If you do have any trouble, I suggest trying several
different iron temperatures and times, different bags, and different
sheets of paper. One of the bags I used seemed to stick slightly
more than the other, although not enough to cause trouble.
Somewhat to my surprise, there were no plastic-type
smells produced by the ironing of the plastic. In fact, there
were no smells at all.
Also, you wouldn't even need an electric iron for
this, since the original irons were simply heated on woodstoves.
I have a few suggestions for improvements and expansions.
The first is to use larger sheets of paper. That way you could
iron larger sections or plastic in each batch and save time and
effort.
Second, use multiple bags at once instead of folding a single
one. If you cut the lower corner seams and cut off the handles
as I did you could easily make a thick ten-ply square, twenty
by twenty inches, by stacking five bags. And it wouldn't take
that much more time than making one smaller square.
Third, try including other materials between the plastic layers.
I was able to rip the eight-ply piece a little bit with effort.
If you had strong, thin fibres you could melt them between the
layers and make the composite difficult to tear or cut.
Fourth, try a project without using any sewing at all. The stitches
make tiny holes which water can leak through (although not terribly
fast, as I saw when I checked). You can use the iron to weld seams
together and if you wanted to you could make something like a
raincoat. It would take several hundred bags, but two or three
people working in tandem could do it in a couple of hours, and
it might even go faster once they had the bugs worked out.
Something simple to start with might be a water-proof
hat or bag. For a bag, instead of stitching the edges, place a
piece of thin cardboard between two multi-ply sheets, but trim
the cardboard slightly smaller than the plastic so that an inch
or so of the two layers are touching. Then iron them together.
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