How to recycle old milk jugs and bottle caps into colorful plastic bricks


  1. Make into full-size Lego-style bricks.
  2. Use bricks to make a house.
  3. Sell house to Lego enthusiast
  4. Profit!

Finally, an affordable source of colorful plastic bricks.


Does he turn jugs and caps out of the bricks?


I have been curious about grinding up plastic milk jugs and molding the resulting plastic granules into stuff for YEARS and never even thought to check YouTube for tutorials. I always imagined needing a much more powerful motor to grind them up easily.

Thanks Mark! :smile:


extrude into rod for 3d printer?

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Wasn’t there a kids-play-with-Plastics! type toy a few decades ago? You could form blocks and make simple cars and things? Super low tech proto MakerBot. Sort of e-z-bake oven? I can also vaguely recall a similar technique for making ornaments: a metal outline of a snowflake or angel, you are given several colors of ground plastics, fill in spaces n bake in Mom’s oven.

This would be a fun project, but a couple questions:

  • does the HDPE give off or outgas something nasty when heated to 350? how about 375? mb a spot gets to 425 in my dinky garage sale toaster oven. Will it kill me quicker than ________ (favorite poison)?

  • a milk jug is obviously food-safe, what about my orange detergent bottle?

  • if you make a sheet of it, can you mold it over things a bit like vacuforming? mb make bowls or pots things for the garden?

  • how does it turn since it is a loose-ish aggregate? might break apart along irregular sized granular fault lines?

Turning jugs and caps would be so meta. dude


I would guess, while I ain’t no scientist (although I do believe in global climate change), that breathing anything coming out of that oven would be bad news. That said, a well-ventilated workspace is always a good idea. As for the detergent bottle–a good rinse with water would probably set you up to then grind the thing down.

My worry is that by using it as something to be torn apart in various ways by lathes and the like, that I’d be creating the same problem we’ve already got–small particulate plastic that easily finds its way out of landfills and such and into the food chain. But there’s got to be an environmentally friendly way to use the stuff. Building a shed or doghouse would require quite a few bottles and such, though. Probably kill the blender blade after not too long as well.

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Right off the bat, you’re going to be getting a few whiffs of dioxins and furans whenever you’re subjecting PE or PVC to those temperatures. That’s nasty enough for a start.

The granularity also leads me to believe that this is not food safe - grains are going to be coming off the thing quite easily. That’s without thinking of the other issues like mixing detergent bottles with milk jugs. Don’t use this for kids’ toys or for holding any kind of food.

As I recall, with every recycling, the density reduces. So what was HDPE is now slightly lower grade stuff. I don’t know what the implications for recycling whatever you make from this are.

Still, it’s an interesting idea…


Well you could buy a used toaster oven for the melting and do it outside or in a garage. Also hardware stores sell gas masks (which you should be using anyways if you use spray paint).

This one uses parafin wax:

Loved that thing


Paraffin wax is a lower molecular weight cousin of polyethylene.


Not sure this sold well in the southern states. Things that melt so easily are clearly the Devil’s work.

hmmmm, my version of this seemed so much more crude. mb this is the 80s/90s version
gotta wonder about the outgassing from that puppy
I bet kids who use this wax (har har) poetical about the smell the thing used to give off. Thems were the good ol days.

They say he carved it himself… From a bigger spoon.


I never really understood why the “maker” group has never explored recycling/reuse of HDPE jugs. I mean we have tons of homemade sous vide cookers/controllers, so why not apply that to this? So take a decent length of black iron pipe, find an auger combination (relative to inside pipe diameter) that fits, some end caps, a hole for extrusion, a Y or sanitation Y for raw stock feed, a motor to drive the auger and a heating element. For probably less than $100 you should be able to turn out a decent filament line. You’d need to play with temperature and auger speed but this is essentially what a small yield production extruder is. Of course they usually have multiple temperature zones, and there isn’t any reason you couldn’t do that here it’s just more complex.

I wish I had the time to play with this, but maybe at least I’ve given someone an idea or two.

Also - flat sheets would be hard to do. The best way I’ve seen it done is via an electric frying pan (with temperature control). Pile your stock in the middle, add a barrier (or form) and then apply weight over the whole thing. HDPE never really enters a liquid state, at best you get something like taffy so without pressure to force it spread out you get a melted lump of plastic. I suppose if you were really good with metal work you could build a progressive roller setup and heat them with MOV transformers wired for high current (but you’d need some type of controller to manage temperatures as well).

-and last- Detergent bottles. No, just no.
The next time you get an empty one wash it out. As many times, and with as much cleaner as you feel is necessary. Then fill it full of clean drinkable water. Let it sit overnight. The next day pour yourself a glass. If you can’t smell the detergent in the water I want to know what cleaner you are using, cause I need some.

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