Plastic Smithing: How To Make your own HDPE Plastic Anything (DIY plastic lumber)

Picture of Plastic Smithing: How To Make your own HDPE Plastic Anything (DIY plastic lumber)
How to make really good hard plastic while reusing and recycling plastic bags at home! Via this method, you can make ANYTHING you want to, out of hard, lightweight, real plastic that's astoundingly durable. It comes out very similar in texture to recycled plastic lumber.

best of all, this method involves no fumes!

I'm gonna show you how to make plastic wheels for your robot!

I first heard about stewing plastic bags to make new things from Dave Huebsch's book " Village Assignment " about interesting adventures had while running a charity/NGO (" Common Hope ") in Guatemala. He, amazingly, repaired the bottom weight-carrying main bearing of a washing machine with a big plastic disc made of stewed plastic bags, which actually was such a good stand-in replacement that it held up for several years. (and here are some more Guatemalan Handy Tricks)

I had to try it right away, and the first couple times I just burnt plastic, until I came up with this method.

By the end of this, you'll be able to make yourself a knife sheath, mold around your shoes and make DIY hard-toe sneakers, wheels, bearings, bushings, or any kind of plastic part! Take pictures and post them in the comments!
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babycody2 years ago
I am in to vacuum forming plastic. However the sheets are not cheap. Has anyone experimented with making sheets out of thermoforming plastic such as milk jugs? I work at a company that uses pelleted plastic, and I really want to try this technique on some of those pellets. I have read around 80 comments so far, but have not seen anyone mention using a deep fryer with a temperature control. Does anyone see a drawback to using one?
Wepwopper babycody10 months ago

Hi babycody, I just saw your question about thermoforming plastic such as milk jugs. I used to love to play with this stuff. It melts between 350 and 400 F dry oven temp. It stays pliable for about 10 minutes if you want to stretch or trim it. I've also melted layers into bread pans for door stops. Once it has melted at high temps and cooled, it will not melt again so be sure of the form or melt at lower temps. Once it gets to the liquid state, work with it quickly to press into forms. It reacts to cool air to harded in as little as 5 minutes. Other ways I've worked with it is cutting it into the shapes and soften the edges with a bic lighter.

The HDPE plastic used in apparently is remeltable as shown in that video. I conjecture that "remeltability" may depend upon the type of plastic, though.

those are bottle caps which are normally injection molded at a factory this means those bottle caps have to be made of an hdpe grade that flows well into a mold therfore bottle caps will flow without any pressure unlike milk jugs and detergent containers


i haven't tried it out yet but maybe too much oil. if it's a deep fryer with a basket you will need quite some oil in it to establish contact with the bags.

and another possibility would be the risk of molten plastic bits falling or seeping through the basket. thus either creating a bit of a mess or disintegrating the whole block.
mbear antioch2 years ago
From what others have said in the comments, you can use a deep fryer but you'd probably want to put it in another container of some sort to contain the plastic bags. Something like an empty coffee or soda can.

My theoretical process:
1. Put some oil in the can to act as a mold release agent. Swirl around edges to get good coverage.
2. Put shredded plastic bags into can.
3. Put can into (cold) deep fryer. (If oil gets in the can this is apparently OK.)
4. Turn on deep fryer and set to target temperature.
5. Profit!

No idea if it'll work, but at least it's a start.
funny104815 days ago

i have been doing many experiments with hdpe and i melted down some milk jugs and 5 gallon buckets and bottle caps what you will notice is that milk jugs dont flow as well as buckets and bottle caps do when they are melted the reason is because milk jugs are blow molded and buckets and bottle caps are injection molded hence the higher flow rate of the bottle caps and buckets. however the melted down milk jugs are stronger than the bottle caps and buckets and i did have a lot of luck melting down translucent hdpe containers such as milk jugs you just need to clamp the mold under pressure and you should get very good results i used a cylindrical mold from a pipe and sort of made a piston with scrap metal and i simply melt the milk jugs in the tube and then press down on the piston and when it hardens you have a smooth hdpe round rod i made pulleys this way by turning it on the lathe and gears and the hdpe melted so perfect that it was indistinguishable from hdpe round rod you buy at the store. by the way dont clamp hdpe 5 gallon bottles or bottle caps they will simply flow into the mold without any pressure only clamp milk jugs and other translucent containers under pressure. hope this helps

gaieb1 month ago

If you use an electric skillet to heat the oil with your plastic in a pan sit in the oil you can get very good tempurture regulation.

karen.hoelcle3 months ago

I am very interested in your process. What I would like to know is if you can make bigger items? I was thinking about making a small house or shed basically a work area out of the plastic. I know it will take a long time and I have that but what I need is how can I make a mold for the shapes I would like to use. Any idea???

Karen, just use a brick/clay mold. You can just take some scrap wood or plywood and tack it together, pour in your plastic. Just break the plastic out of the wood when you're done, or make large batches at once and take the cool solidifying plastic out of the mold before it dries completely. The key to building large structures is conformity in the Western world. Clay you can flex, plastic bricks, not so much!

bgoodr bwag1741 month ago

Along those same lines: See which specifically uses HDPE plastic with a wood and clamps to force the softened plastic into thick sheets.

I haven't made this yet, but may I suggest that a way to eliminate the greasiness would be to make a double pot assembly like double boiler except that the inside pot is smaller and set INSIDE the outside pot. Fill the gap between the two pots with oil so the inside pot is in dirrct contact with the inside pot.

To be clear the oil needs CONTACT the outside surface of the inner pot to transfer heat, you DO NOT want to heat he oil until it smokes.

As for the parafin idea, DANGEROUS, heating parafin too much ( usually by a double boiler to avoid overheatin and sudden ignition ) may suddenly burst into flame and you'd have an oil fire whose fuel could splash, stick and solidify into molten flaming globs on anything it touches including you.

Finally a second hand deep frier with temperature control may be ideal, you may be able to eliminate the oil all together. Some diy jewelers have made injection wax pots by clamping the lid and using a manual air pump to a GENTLE positive pressure for injecting hot wax into mold for lost wax positives.

Too hot wax or smoking oil BAD, hope this helps someone.

Hope this helps.


Just in case anyone is wondering about different plastic safety:

Happy crafting :)

JayallanB3 months ago
Im looking for a way to make a tridimensional chess board star trek style, would using plastic in this manner work for that. As far as sturdiness goes?
Im thinking if it turns out to rubbery it will just bend over and wouldnt hold the weight of the boards.

I'm no academic, just a simple soul who's interests are in environmental issues. I am responsible for loads of recycling and this idea of yours is very exciting. May I ask you to check what I intend to do.

Large pan with a little oil inside.

Place plastic bags in a metal loaf tin (greased.)

Place loaf tin in pan of oil.

Heat at 350 degrees until mushy.

Press plastic mush with weights.

Allow to cool in the loaf tin.

Is this right?

It seems fine to me. I would be careful about the plastic sticking, but if it's a low temperature then you'll be fine.

Use the canola oil in a deep fat fryer as a double boiler to get the higher temperature, but no contact to the oil. Instead of a basket, use a thin walled aluminium sauce pan( better conductivity) shred the bags in a cheap shredder and dont worry abouy it overcooking if you have a thermostatically controlled fryer... Just let it sit for a while till it all melts together... ;)
awnal7 months ago
Hi. Id like to use this to make a foregrip and buttstock for a paintball fun wpuld this be durable enough to withstamd the force of being shot amd being held tightly while running and combat and thungs of the sort? And how do i shape it? Can i carve it down to size?
pbilling7 months ago


Nov 17, 2014. 6:54 AM
Recycled HDPE bricks

Building bricks for housing using recycled HDPE sounds very interesting. To make it viable you'd need to do it on an industrial scale and have lots of plastic on hand. I don't know Bay island but if they are swimming in waste plastic then maybe. You'd also need to estimate the cost of the energy to heat the plastic. It is conceivable to build a large 3d printer that can directly print the walls of the house. I've seen some on the 'net only but they can print maybe single rooms I think around 14 feet in diameter (kinda like a plastic yurt). I wonder how you would have to coat the plastic to provide UV protection. An interesting set of problems. I wish you the best in this effort.

Starsword77 months ago

Great Idea, I love It. To make the wheel more uniform you could also clamp something circular on top of it while it is cooling.

Hello, I am in Kara, Togo West Africa, trying to stop malaria in this city of 100,000. The root cause is plastic bags that block the drainage canals, and rivers, making dams that allow mosquitoes to lay larvae. Presently, the locals burn some of the plastic bags, but never enough. This pollutes, and burning plastic cannot be healthy. I would love to have the same process done using mirrors, or to make some form of solar concentrator that melts the plastic down into manageable size. Then maybe we can make hoe handles, or shovel handles from the plastic, if really good we could make roof rafters. How to use mirrors to concentrate on plastic oven cheap? I think an oven melts plastic different than putting onto a burner. Andy Lee Graham / hoboontheroad AT /

hobotraveler > make homemade rocket stoves. Well tended fire is as efficient as a good stove. Melt your plastic and re-use.


You could have a look at something like this

no need for electricity then :)

HoboTraveller, you most certainly CAN concentrate enough solar to do this.
One way would be to use a dish shaped frame (such as an old style dish antenna) and attach the mirrors to it - they would generally focus on the dish's central point, put a pot full of plastic there and, I dunno, a metal funnel at the bottom? It'll probably burn from time to time but should work.
Another way might be to use the focusing screens off of large TVs that have been thrown out.

You can find instructions for these kinds of large solar devices, just look for fun terms like "solar death ray" and the like.

pdyson7 months ago

I think the best way to make this work would be to build a small rocket stove get a pan with a side tap use the tap open as to fill moulds and feed into HDPE threw the top of pan cannot see a need for any oil myself needs doing outdoors

pdyson7 months ago

just had a ten minute think about this one, can you not build a small rocket stove with a pan with a side tap on top so you just fill the pan with HDPE 2 inside it thus it will fall like a hopper as it melts threw the side tape into your mould? seems real simple to me without using oils

davejuniortwo10 months ago

can we use nay kind of plastic for this?

anything made of plastic


A lot of guessing going on in the comments.

I have found that HDPE (code 2) and polypropylene (code 5) both melt non-toxically in an electric oven set to 180-210 degrees celsius - it varies quite bit between samples. It cools quickly, so you have to work fast to mould it, it is soft but not fluid at those temps.

normally i just melt plastic items like bags, pens, and unwanted things with lighters and turn it into something useful. the only problem is that theses alot of smoke and the smell of it hurts

mmohesky1 year ago
Will it work with a pan instead? We don't have any pots to spare.
sypage1 year ago
About how many plastic grocery bags would you estimate it took to make that disk?
augapfel1 year ago
I'd probably try to shred the plastic bags and bottles in either a blender or a paper shredder or maybe a food processor so I started with a rather uniform raw material.

I'd also probably use a potato masher instead of a fork to really blend and mash the gooey plastic into a more uniform and consistent blob.

Finally as it sounds like forming the plastic into the mold is a challenge I'd probably heat the mold. I think I'd place it in the basket of a steamer and use the butt of a small screwdriver or a wooden dowel or a pestle to pack the plastic goo into the mold and press out any air.
stasterisk (author)  augapfel1 year ago
cool can you let me know how your experiments turn out?
um_dustin2 years ago
Bear with me... Have you tried melting on the stove just to homogeonize the plastics, then using a double-boiler in the overn to melt the plastics into a rough form that only needs minimal cleanup?
appledaquel2 years ago
By the way, this is my e-mail add. You can suggest something but very specific and general about the question. I'll wait for it.
appledaquel2 years ago
I'll just ask if these plastics can turned into a jelly-like or a silicon-like object that seems to be a cellphone gel cover? But it doesn't mean that it should turn into a CELLPHONE cover. I just need it for our research. You can answer me through my yahoo mail.
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