This collapsible canteen is made from six mill polyethylene plastic sheeting (painter’s plastic available at home improvement stores), #215 O-rings, and a water bottle. Fusing the plastic is done with a Food Saver vacuum. It is surprisingly strong. I can stand on it without it bursting (160 lbs). The larger pouch holds 2 quarts of water.
For safety info on polyethylene click here
Step 1: Get Your Guide Out.
Inside the Food Saver there is a small tray for catching fluids during the sealing process. This tray is a good guide to lay out your sealing area. As long as your pieces fit within this tray you'll know it will seal when you close the machine. I used scissors to cut out squares from the polyethylene sheeting. Since the sheeting comes folded over, cutting once gave me four squares of plastic.
Step 2: Stretch the Sheeting.
Take two of the plastic sheets and hold them together with your hands on each side of the center. Force the sheeting down over a cylindrical object. The cylinder must be smaller than the opening of the water bottle. I'm using the handle to a musubi press but you could use a felt marker which has a similar shape. Once the plastic is stretched about half an inch, cut the very top disc of plastic out.
Step 3: Cut the Bottle
This part is very simple. Take a pair of scissors and carefully cut the bottle open near the cap. See the pictures. Keep cutting until you have about an inch of bottle left, measuring from the threads.
Step 4: Trim the Spout
This next part will trim the bottle to the proper length. Place 2 O-rings around the neck under the collar. Invert the remaining plastic towards the o-rings. Use the heel of your hand against your counter to further invert the plastic. Once the plastic is contacting the O-rings you can score a line with Razor blade. Stack two pennies and place the razor on top. Rotate the spout around the edge of the blade to score a line. You don't have to cut all the way through. This is just a reference mark. Next, un-invert the plastic skirt and trim it following the score line. Remove the O-rings.
Step 5: Install the O-rings
Force the plastic over the spout. It should be snug all the way up to the threads. Slip to O-rings over the spout making sure they are underneath the plastic collar. This will be a tight fit. On the underside invert the plastic around the bottom O-ring.
Step 6: Fuse the Edges
Food Savers have been around for a lot of years. If you're not familiar with one basically, it is a machine that removes air from a plastic bag so you can store food longer. For this project we don't have to remove any air were just using the sealing element.
Line up the sheets on top of the sealing element, close the lid, and press seal. You should now have a clean fused line. If you have any trouble getting any part to fuse you can always flip the pouch over and seal it again. Use a damp cloth to cool the seam before pulling the plastic away.
Step 7: Trim and Test
To finish it off use a straight edge and razor. Cut the excess off at the edges of the seams. Also trim the excess plastic from the spout.
I tested this by standing on it. Even a single ply pouch withstood my weight, 160 lbs.
Thanks for reading.