PVC - PVC as a thermoplastic

It turns out, PVC isn't just my favourite product to work with, it's also a thermoplastic.

Who knew?

I should have remembered the thing I read back when I was making aquaponics grow tubes, but you don't know what I'm talking about, so there's probably no point in referencing it.

But on the up side, there is a point to this post.

And that's that PVC is even more excellent than I first thought.

It turns out (not my idea) that PVC can be heated, formed into a new shape, then cooled so it sets and stays with it's new shape.

You've gotta be happy with that.

PVC, but whatever shape you want!

I started by holding part of the delivery system from my demand fish feeder under a candle until it got a bit hot.

I'm always torn between the desire to keep a museum of the things I build as part of doing this "120 things in 20 years" caper, and grabbing a lump of kit from a previous project and reusing it at the expense of said project.

Oh well, I guess if it's worth building, it's worth building again.
The next step was to squish it a bit.

The steps after this include trying to make it fit the fillet knife I keep ominously lurking in my little tackle box.

That'sit there in blue.

I say ominously because when I'm fishing, it tends to be used to hack at somewhat suspect portions of slightly off bait sitting in the sun, then when I get home, I expect it to shed it's immuno-challenging persona with a quick wash n a soapy sink, and stop threatening to cut me and give me some hideous infection.

I also expect it to get suddenly sharp enough to fillet fish.

Sometimes I expect too much.

But this time it turns out I oddly expect around about what's reasonable to expect.

This is mainly due to my sudden understanding of how to make stuff sharp. I've been using a honing steel for the last 20 years to keep my kitchen knives useful, but for some reason, suddenly I now seem to be able to make them half again as sharp. (((see chunking) actually see the top of the chunking article because that makes more sense) or this if you want to skip the links...

If you learn Morse code, you learn it gradually for a bit, then suddenly instead of thinking of the word "and" as...

dot dash blah blah
blah blah blah
blah dash etc

you start to know it as a single entity in much the same way as you originally knew the individual letters. ie the group "and" becomes the 27th letter of the alphabet. The result is that the learning process is non-linear, and you tend to gain new ability in "chunks" rather than gradually.)

Why am I distractedly talking about chunking motor tasks?...


Sharp is much better.

And oddly safer.

Anyway, the result is that now, more than ever, I need a sheath for the razor blade that rattles around in my tackle box and kitchen.

The knife in question is only an inexpensive thing, and it doesn't hold an edge for long, but it does readily allow itself to take on a scary sharpness. I guess there's a compromise between gaining an edge, and keeping an edge, and this inexpensive fillet knife has chosen as it's lot in life, to be way sharp. At least for a bit.

Quite useful for fish filleting really.

PVC is a thermoplastic!...

The "holding it over a flame" thing works a bit, but it's a little tricky softening the entire thing so you can bend the entire thing all at once.

But boiling water made that a whole heap easier.

If you don't have an enormous pot of boiling water, I recommend you send any kids safely away for the afternoon, and just dump boiling water all over the place in order to heat up your PVC.

It actually doesn't take that much.

I'm guessing a hair dryer would do it.

I used half a cutting board, and a sizzling steak hotplate holder to squish it flat after I heated it to bendy point.

You could also just step on it.

It's quite soft, and cures to it's new shape in only a few seconds.

The result was something that looked a lot like a folded flat length of PVC pipe.

Actually this is (obviously) the result of a different method, but both ended with a folded length of PVC tubing.

This one was done with the aid of two clamps, and pouring boiling water all over the house.

There are probably a dozen more ways to do it.

Heat it, then squish it flat.

This post has derailed a bit, so to re-cap, I'm making a knife sheath from PVC pipe by heating it and reforming it to shape.

Place your knife over the top of the flattened PVC envelope, and loosely trace around it with some kind of marking device leaving around a centimetre of excess white space around the blade.

I used a pen, but you could also use whatever marking method your culture enjoys.

Next I cut out the shape with tin snips, scissors, and a hacksaw to test as many methods I could find at hand. That's why this photo actually came before the last.


time can do that.

The result was the start of a pretty convincing knife sheath.

I drilled a few holes.

I added a loop rubber band made from a slice of bicycle tyre inner tube (bicycle tyre inner tube rubber bands last around 25,000 years longer than normal rubber bands)

The loop will hook over the handle and act as the fail safe, and might allow me to wear it in a way that might be a little more practical than hanging it on a belt.

And a few more holes to snug it all up tight to the blade with some multi-strand artificial fibre twine and we are done.

I count this as a total success.

Much less dangerous.

And now probably safe enough to take on an epic adventure.

It will still need to be washed after using it to handle bait, but at the moment I cant see a way past that as a compromise.

If you try it yourself, make sure there is a bit of space between the PVC folds at the sharp end to allow water to pass through when you wash it, and also make sure the bindings pull the PVC together tight enough that the blade can never touch the binding twine. The easiest way to achieve this is to not take the bindings all the way to the tip of the sharp end. And to stick something in the end when you are heat-forming the sheath. However you do it, try to make sure you can see through the sheath when it's empty, to allow rinsing the sheath.

I found that after it was finished, heating the entire thing while the blade was removed, and bending it slightly from end to end, made the blade sit a bit tighter. Enough so that you could could hold the sheathed knife upside down and shake it, (without the safety rubber band) and the knife would not fall out of the sheath.

A total success, and definitely some tech that I will add to the ever growing grab bag of tricks that I might employ to solve something, somewhere, one day.

120 Things in 20 years just came back from a quick trip into the future, and found it's all made of PVC...

and there's some 3D printed concrete housing.

but the future's definitely made mostly of PVC.


  1. You probably already know this, but just in case you've missed it somehow, you can make an astonishingly good bow (the kind for shooting arrows) from PVC. I know this because my brother showed me his. I thought I had a photo of it, but I can't find it right now. Google has lots of them, though, so you can ask it. Because, PVC!

  2. I have to add another comment, because I forgot to tick the "notify me" box on the first one, and I might get busy adulting again and forget to check on my own. So just ignore this. The important stuff is in the other one. :P

  3. I've been thinking of making a PVC bow.

    There is an introduced pest species of fish (carp - full of bones, tastes like mud)) that's infected the River Murray and that humans are encouraged to remove from the river and feed to the birds or use as bait to catch better tasting things.

    Bow hunting for them is a thing people do.

    If I ever get around to my epic solar boat trip I plan on having a bow, but I thought I'd make it on the boat out of bamboo.

    There's bamboo growing on the banks.


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