Many of us use plastic in our projects, but did you know you can melt down and reuse much of the plastic found in your house? In this instructable you'll see how to recycle plastic to be reused for whatever you want.

Step 1: What Type of Plastic Can Be Reused?

For this method we will be reusing high density polyethylene (HDPE) plastic. You can identify this plastic by the recycling symbol on the bottom of most plastic containers. HDPE will be identified by a small "2" in the center of the recycling symbol, and will sometimes even be accompanied by "HDPE" written next to the symbol.

When compared to ABS plastic:


  • density - .958g/cc
  • tensile yield strength - 20.6MPa
  • melting point - 129 C


  • density - 1.05g/cc
  • tensile yield strength - 41.5MPa
  • melting point - 220 C

While HDPE is not as strong as more widely used polymers such as ABS, it is good for low stress applications such as project enclosures, lightweight mounting solutions, and more. And the best part, it's free!

Step 2: Materials and Tools

To start this project you'll need:


  • HDPE plastic in the form of containers and/or plastic bags
  • Baking pan
  • Wax Paper
  • Non stick cooking spray


  • Scissors
  • Oven or toaster oven
  • Gloves (preferably welding gloves or similar heat resistant gloves)

Step 3: Preparations

If you decide to use plastic containers such as milk jugs you'll need to cut up the plastic into smaller pieces. Using your scissors cut the plastic into nickel sized pieces. If you use plastic bags it helps to tie them in a knot. Plastic bags tend to shrink in peculiar ways when they melt, knotting them makes them easier to work with. Once you've cut up your plastic into small pieces preheat your oven or toaster oven to 350 degrees Fahrenheit. Make sure you do this in a well ventilated area! While the plastic shouldn't release an excess of fumes if done at the correct temperature, any fumes it does release will be nasty and should be avoided.

Next you'll want to grab what ever you decide to use to melt your plastic in. An old cooking sheet or pan can be used. Line the pan with a sheet of wax paper and spray a light coat of non stick spray or similar lubricant across the sheet.

Another option, if you've built the furnace shown in my last instructable, you can cast aluminum molds for melting down your plastic.

Step 4: Time to Melt!

Place your plastic into your pan or mold and place in the oven. Cooking should take between 30 minutes and an hour depending on your oven. Keep an eye open for signs of burning and adjust the heat as necessary. The plastic will go soft and malleable as it melts. Once all of the plastic is melted you'll want to grab your pan or mold out of the oven (make sure you have your gloves on!) and check for gaps and voids in the plastic. If you want cleaner edges on your plastic, fold the edges of the plastic over on itself. Once you're happy with your plastic, throw it back in the oven for another 10-20 minutes to melt down and make the part solid.

Once your plastic is done you'll need a way to keep pressure on top of the plastic while it cools. Otherwise the plastic will try to buckle and warp as it cools. This can be done with a couple of pieces of wood and either a couple of clamps or a heavy weight.

Step 5: Make Something!

Once your plastic is cooled it can be used for whatever you can think of! You can trim it and make plastic stock for later use, or cut and machine it into anything you come up with. I've found that a small jig saw works well for cutting and 80-180 grit sand paper for shaping.

Go and use your plastic for your next project and thanks for checking out my instructable!

<p>I like the idea of melting plastic. I've been thinking about making blocks with melted plastic and building a shed with it. I crochet with plastic bags, I cut them into strips, across the bag, I link the strips together, roll it into a ball and crochet. I make rugs and bags.</p>
<p>I wonder if I chip/shred/cut it up and put it in a metal tray in a solar oven and leave it for the day while I went to work if it would it melt down into the pan and leave a flat sheet of plastic. Might have to build a solar oven and cut up the milk jugs to find out. Anyone try something like this. </p>
<p>It looks like a great loss of energy, when used just for the sake of recycling plastic.<br><br>But could be done in winter, though:<br>while melting the plastic, you will heat up the house too!</p>
How do you think plastic is normally recycled?
Even if it is recycled this way (though i doubt they use kitchen ovens and melt 1-2 kg of plastic), the economics of scale would make industrial recycling more effective and less wasteful. <br><br>All this topic stresses the issues of pervasiveness plastics and it's recycling... Too many problems off the plastics.
<p>Shouldnt do it inside.</p>
<p>Yup, good point, as the fumes are not good for your health, most probably. In that case, I would think of other possible recycling methods - this one based on melting is a huge waste of energy, I think...<br></p><p>Anyway, biodegradable PLA is the future for the plastic bags, I hope. At the moment it is better to avoid plastic bags in the first place (e.g., switch to cotton bags, which are more durable and sustainable).<br><br>PS: this is not to criticize the author! Just &quot;my 5 cents&quot;)</p>
<p>It is less wasteful then tossing in the trash but I think this would make a good source of machinable plastic for prototyping parts and it will be cheaper then buying new plastic. If you have a use for the stuff this is a good idea and no more wasteful then baking a potato. </p>
<p>&quot;Two cents&quot;...No criticism...Just getting mine in, as well. :-)</p>
<p>Lol, thanks) /<br>It's been a literal translation from <a href="http://translate.academic.ru" rel="nofollow">http://translate.academic.ru</a>/мои+пять+копеек/ru/en/1<br><br>Lesson learned, I guess, thanks)</p>
<p>A good point!</p><p>:-)</p>
<p>there is a site on the net that has all the blue prints for making anything out of recycled plastic.including the machines from shredders to extruders. check out precious plastic.com</p>
Cool, I am busy getting the parts together to build the shredder. Also very tempted to buy the DIY kit from Filastruder
<p>Ah, Now I'll I need is a fillement extruder :D</p>
Hi dan3008,<br>Check out Preciousplastic.com. They have open source plans for a shredder, extruder, injection mold machine and compression machine.
I've got a copy of tgeir plans saved on my desktop :)<br>Its only time and finances stopping me already having one :)
<p>can i melt it in boiling water by adding salt to the water to raise its boiling point</p>
<p>No. The so-called melt temperature of hdpe is about 350 degrees F. The boilding point of salt water is only a few degrees higher than unsalted which is 212 deg. F.</p>
<p>I have a broken plastic gear I need to replace. It costs $45 just to have the company look at it to decide &quot;yep it is a broken gear&quot;. Before they will send me one. Of course I have topay for shipping each way as well.</p><p>Ok so this gives me an idea for replacing said gear. </p><p>Thanks for this :) Two thumbs up :)</p>
<p>hmmmm, I carve things out of wood, dolls, animals etc I have seen the &quot;ivory like&quot; plastic that is sold on eBay to carve I wonder if this would work? Also could be made into dollhouse furniture maybe sounds like great uses for me thanks!!!</p>
<p>To be a bit pedantic, you're not making plastic....<br><br>It's already plastic.</p>
<p>I saw a post where you can make machinable wax you take paraffin wax and melt it then add plastic bags then pour it in a mold. </p>
Ok wait a minute. <br>If grocery store bags are #2 HDPE, why won't the recycling center take them?
<p>A few reasons. The recycling number doesn't mean it gets recycled it just says what it's made of. That's important since you don't want mixed plastics and aids the recycling center people sorting stuff on a conveyor. They can't spend the time ($) examining every pc of plastic moving down the conveyor under a microscope. Mixed plastics don't have a lot of uses the same way mixed ground up steel and aluminum cans doesn't have a lot of value.</p><p>2nd there has to be a market for the particular type of plastic on the conveyor. PET soda bottles are easy to identify on the line relatively clean without looking at the tiny numbers and get a relatively unmixed bales of plastic for further processing. There is a buyer for that.</p><p>3rd plastic bags don't behave on a conveyor line they blow around get caught in mechanisms and gum up the works. They fill with air and take up a lot of space and don't weigh much. Thin film larger area low density... bad return on labor. Not all bags are made of the same stuff and many plastic films are actually many layers of different stuff. So you can't say put all plastic bags in this chute.</p><p>4th. since they're thin they don't grind up into approximately grain of rice size chunks to be useful in plastic processing equipment. Extra post processing $.</p><p>So it's makes sense to say don't put #2 bags in the recycle bucket since we have to pay someone to take them back out and put them in the land fill anyway. Which isn't to say paper bags are a better environmental deal.</p>
<p>I think paper bags are a way better environmental deal. They require less energy for being manufactured and are fully recyclable. Even if landing in landfill, they degrade quickly and without releasing unnatural chemicals. You can even compost them. Much of the paper (not even half, but still a significant amount) produced in developed countries is made from cultivated wood, which is a renewable resource, unlike oil. None of these applies to plastic bags.</p>
<p>Necessity is the mother of invention re: &quot;So it's makes sense to say don't put #2 bags in the recycle bucket since we have to pay someone to take them back out&quot;. Someone? or something? </p><p>. </p>
<p>From the info you've given about plastic bags paper sounds pretty good in comparison. Paper can be recycled into lots of things and bio-degrades. Depending on how the paper pulp is obtained it can be sustainable. More-over, not many things makes a city look more trashy than plastic bags caught in the trees.</p>
<p>I have asked myself this exact same question. Recycling centers (at least American ones) are bizarrely specific.</p>
<p>Compared to what?</p>
<p>You ought to see what they require in Japan.</p>
<p>Haha, I don't think I want to.</p>
<p>Stuff like that gets caught in the equipment</p>
<p>Huh, you know I never thought about the sorting equipment. I guess that's why they do have plastic bag recycling containers at grocery stores. Since there's no sorting they can probably just dump all of it in and melt it down.</p>
<p>They generally will, you just have to bag them up (stuff a bunch of them into one bag).</p>
<p>Does PAM work for the non stick spray?</p>
<p>Try parchment paper instead of waxed paper. You don't need the cooking spray and the plastic comes off nice and clean.</p>
<p> like your sheet material i made a structtable on making block matreal </p>
<p>great instructions I will be trying this soon</p>
<p>I've used a heat gun in the past to melt certain plastics. I've used many types of plastics (re-purposed) in order to do Plastic Welding and repair other plastic pieces, or create molds as well. Good Instructable!</p>
<p>Great idea, so mold them into sticks for use in glue gun? Will make some bad fumes when used in a gun but if you prepare for that it is a great idea.</p>
<p>Typically you'd extrude push it thru a round hole and pull on what comes out to make a long pc. PP and PE don't really stick to anything so it wouldn't work like a glue stick. You can use a thin stick of this kind of plastic with a small diameter heat gun and weld similar PP or PE pcs of plastic together with it. Glue doesn't work very well on PP or PE. </p><p>Most plastics don't requiring anything other than normal industrial building ventilation when molding with it. More air turns than a house though. Some like PVC are an issue particularly if you overheat it for a period of time. </p><p>Plastic bags get a bad rap mostly because people don't dispose of them properly and they end up blowing around. Or you're friendly waste disposal company takes it on a barge and dumps it in the ocean. Energy wise, sanitary wise, water consumption wise they aren't worse than paper bags. It probably makes for sense to make something useful like a plastic bags rather than burning off the propylene and ethylene gas when you're processing oil and natural gas.</p>
Could this be done on PET bottles?
<p>This is really useful, and gives creatives a way to reuse many items that would end up in the pit too soon. It's simple enough to do consistently if plastic is needed in your designs and a great way to plant the reuse and waste conscious seed. Love it! I see a lot of safety concerns, which is def valid. I will be and I advise that peeps do their own research on the safety of melting thermoplastic types. It's always a good idea to educate yourself when you have unanswered questions about safety. I've already learned a lot from the comments below! Tx for posting!</p>
<p>some plastics will emit fumes even without getting heated, others don't. Plastics often contain solvents. But no matter what, it's not advisable to heat plastic in something you use for food. There's no guarantee that plastics are what they claim to be and some of the chemicals that can be found in plastics are pretty nasty. </p><p>So I'd keep it away from food and dishes, and would only melt it in really well-ventilated areas. </p><p>And wash your hands! (after)</p>
<p>HDPE mentioned in the instructable is what's often used to make a cutting board. Safe for food contact. </p><p>If you're concerned about phthalates I think they are mostly in PVCs and do leach out, although you'll also find them in food medicine cosmetics etc. BPAs mostly turn up in epoxy (can liners) polycarbonate and PVC.</p><p>PTFE (sometimes call Teflon) does break down into some nasty chemicals but they melt at a very high temperature. To make a safer non stick surface on cast iron cookware you season it with vegetable oil which turns into you guessed it... plastic ;)</p>
<p>I rarely use vegetable oil. Fatty foods like bacon and olive oil or even butter work just fine for seasoning cast iron.</p>
Thx that sounds very thorough. Still I wouldn't trust that plastics always contain what they're supposed to and I don't trust that we know all about possible effects of plastics on the human organisme either. <br>Personally, I'm not using any plastic cutting boards, but mainly because I'm old-fashioned :-)<br><br>All in all, melting plastics at home sounds to me like something of the &quot;don't try this at home&quot; drawer. Needless to say that accidents with hot, semi-liquid plastics can give some extremely nasty burns, as it sticks to your skin and won't peel off until it's cooled and hardened. That takes a long time, believe me, I've tried it.
Nice idea, but why do you work so messy. The result could be so much nicer.
<p>Could we mold it into a doll let's say?</p>

About This Instructable



Bio: I'm a mechanical engineer seeking to further my understanding of automotive design. My first love is cars, but I enjoy designing and building a ... More »
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