HDPE Blocks From Plastic Bottles




About: Italian maker, law student, DIY enthusiast. I make lots of projects, I fix lot of stuff and I like to save and reuse materials taken from broken stuff.

Hi everyone!

In this instructable I'm gonna show you how to recycle HDPE plastic bottles and jugs to create blocks that can be used in lot of different ways.

Every day each of us uses and throws away lot of plastic stuff...let's change this!

Dave Hakkens (which I suggest you to follow and check his job) is an awesome guy who made lot of videos about recycling plastic. He shows you how to collect, melt and work plastic stuff in order to create new things. In his videos he also shows how to build machines to shred, extrude, inject and compress plastic but if you just want to start recycling a couple of bottles, you can follow this quick guide to do it at home in a very easy way.

P.S. I entered this instructable in the "Plastics Contest" and in the "Reclaimed Contest". If you like this guide please vote for me! I really appreciate it!


Step 1: Materials & Tools


- HDPE bottles and jugs

- scrap wood (for the mold)


- clamps

- baking paper

- high temperature resistant gloves

- scissors / utility knife

Step 2: The Mold

You don't have to get crazy building the mold.

Since we are going to melt the plastic into a block we just need a simple box. The more accurate will be your box, the more accurate will be your HDPE block.

As you can see from the pictures above I used scrap wood that was laying in my workshop, and I covered every inner surface of the box with baking paper. This will be important later in order to remove the HDPE block from the mold. Wood is a porous material and melted plastic is a very sticky material so you don't really want that they come in contact.

Step 3: How to Cut the HDPE Bottles

First of all HDPE; what's that? how can u recognise it from all the other type of plastic?

HDPE stands for high density polyethylene. It's a quite common material used specially in the production of plastic bottles and corrosion-resistant piping.
As you can see in picture#1 you can easily distinguish it from other type of plastic thanks to the number "2" as its resin identification code.

After removing the labels and washing the bottles from beverages and soaps residues we need to cut them into small pieces. The smaller the better since they'll take less time to melt. You can use a utility knife and a strong pair of scissors to do that.

I usually start with the utility knife by cutting away the neck (photo#2) which is the stiffer part, then I cut away the base, and finally the handle.

To finish the job you can use a strong pair of scissors to cut the bigger pieces into smaller ones (photo#4)

Step 4: Bake It

Each type of plastic has a different melting temperature.

Dave Hakkens did a great job studying every type in order to individuate the right melting point (you can see his job here).
I found out that in my oven HDPE usually melts around 180°C.

While preheating the oven, put your a piece of baking paper onto a baking pan, and place your cut pieces onto that. Finally place the baking sheet in the oven and check it every 10 minutes.

Step 5: The Marble Effect

The first pattern that I'm going to show you is also my favourite one; the Marble effect.

After 10/15 minutes if you see that the plastic looks sticky you can remove if from the oven. Use a pair of heat resistant gloves and rotate the HDPE (with the left hand rotate it clockwise, and with the right hand in the opposite direction) than fold it in half and do another rotation (photo#2/3).

Be quick (it cools down quite quickly) but pay attention! It is really hot and sticky.

Once you get something like what you can see in picture#4 you can put everything back in the oven.

WARNING: Use the gloves! If it ends on your skin wash it immediately with cold water to reduce the pain.

Step 6: Clamp It

After 10 minutes you can take it out of the oven and you can put it inside the mold.

Clamp it as hard as you can and come back every 5 minutes to tighten the clamps. HDPE shrinks while it cools down so in order to get a flat block you have to tighten the clamps frequently.

Step 7: The Marble Block

Here it is the result after 2 hours of cooling down.

As you can see from the pictures the twisting-rotating technique that we used before created a beautiful marble effect. I really like this method because you can see all the different colors used.

Step 8: The "Camouflage" Effect

This is another pattern. I call it the camouflage effect.

This is easier and safer than the marble effect because it doesn't need to be worked by hand.

Like in Step5, after 10/15 minutes, if you see that the plastic looks sticky you can remove if from the oven.
This time we will use the folding technique. Always paying attention (and always using high temperature gloves) lift the baking paper on one side and fold the plastic on itself (photo#2).

Repeat it on the other side and put it back in the oven.

Step 9: Clamp It

After 10 minutes of baking, remove it from the oven, fold it one last time making something like a chinese spring roll (photo#1) and put it inside the mold.

As seen in Step6, clamp it as hard as you can and come back every 5 minutes to tighten the clamps. Then leave it to cool down for a couple of hours.

Step 10: The "Camouflage" Block

And...here it is the result. As you can see it looks like a camouflage pattern.

Step 11: What Can You Use Them For?

These blocks are incredibly strong, stuff and heavy. You can use them in different ways.

In this photo#3 you can see that I made a knuckle punch, a fidget spinner, some keychains and a spinning top. As said in the Intro, you can check preciousplastic.com to see other products and techniques to apply to HDPE like the cool HDPE kitchen tiles of photo#1.

Step 12: DIY Spinning Top Toy

Here it is an example of what you can do with a single bottle of soap.

First of all I removed the label and I washed very well the bottle getting rid of all the soap residues. Then I melted the plastic into a thin block (following the method shown in the previous steps), and I flattened it with the router until it reached the thickness of 5mm (photo#2).

I drawed a quick spinning top made out of 3 pieces, and I glued the template to the HDPE block. I cut all the pieces following the lines with a scrollsaw, and I sanded by hand all the edges to remove imperfections.

After 2 hours of transforming the HDPE bottle into a block, and after 20 minutes of working on it, I ended up with a cool disassemblable spinning top.

I hope you liked this guide and I hope that you will try to recycle some plastic bottles transforming them into new cool objects.

Thank you for reading my Instructable. ;)
Feel free to comment and ask if you need to know something!


Reclaimed Contest 2017

Second Prize in the
Reclaimed Contest 2017

Plastics Contest

Second Prize in the
Plastics Contest



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    192 Discussions


    2 days ago

    Is there any other way to melt the plastic instead of heating it in an oven


    1 year ago

    Would it work if I put the plastic pieces into a baking tin and heated them in that until they soften, and then just let it cool before removing from the tin?

    2 replies

    Reply 4 weeks ago

    You have to compress them to achive uniformity and a good bond. If not it will be like a plastic sheet of swiss cheese.


    Reply 1 year ago

    you can definitely try. I never done it that way but maybe it could be an alternative process

    Oh yeah, its slick after formed so you might want to give it a texture for grip. As a knife handle it would last 1000 years to Forever.


    1 year ago

    two question:

    when the HDPE is in the oven developes toxic gas?

    is possible to cut the final material or sands down it?

    1 reply

    Reply 4 weeks ago

    When you exceed the max temp it will smoke. You can cut it with a scroll saw, jig saw, its sand able and can be formed with a heat gun. Its mold and mill due resistant and water proof. floats also as shown by the pacific garbage patch.


    Question 1 year ago on Step 1

    Ive been looking and can't seem to find an exact answer, are bottle caps off of pepsi/coke bottles hdpe?

    1 answer

    Answer 4 weeks ago

    From what I've found they are #5 PP poly polypropylene. I get enough material from just house hold cleaners and milk jugs.


    Question 1 year ago

    question here, is it possible to use HDPE plastic block as construction brick? the average temperature in my country is 26-30 Ceclcius. also which material work best? High density polyethylene, Low Density PolyEthylene, Polypropylene, or Polystyrene?

    1 answer

    Answer 4 weeks ago

    HDPE blocks are now being used as construction materials in undeveloped countries in block form. Makes sense because it has a long life even in UV rich conditions.


    Question 6 months ago on Step 10

    Are there any fumes when melting plastic in the oven and if so how do you protect your self from it?

    1 answer

    Answer 4 weeks ago

    From my experience the only time HDPE "off gases" is when you exceed its max temp and it starts burning. There is no odor from the plastic but you do get what ever fragrance was in to container. Mine smells like lots of different soaps and shampoos.


    6 months ago on Step 12

    Muito bom esse post. Esse processo pode ser feito com outros tipos de plásticos?


    Question 6 months ago

    Has anyone made a mold from 3D prints? Not sure what type of filament would withstand the heat?


    Question 1 year ago

    I feel like it would be cool to make like a phone case or something like that. I don't know how I would make the mold though. Any tips?

    1 answer