Plastic to Pride Flag (Easy Upcycling)




Introduction: Plastic to Pride Flag (Easy Upcycling)

About: I want computers to be wilder. Running a Jungle makerspace in Panama.…

This is a super quick how-to letting you know how you can turn turn garbage plastic into a rad rainbow! We used PLA from discarded 3D prints, but you can also safely do this with #2 (HDPE) #4 (LDPE) or #5 (Polypropylene) plastics as well (Which are all very common garbage!)!

For those who want to get straight to it, watch the quick video or read these basic instructions right here! but we will also elaborate on more ideas and tips in the later steps!


  1. Source plastic of many colors (we used old PLA from 3D printer companies)
  2. clean and sort by color
  3. chop up into smaller bits
  4. melt between baking sheets (350F for 15 mins for PLA)
  5. let cool between something heavy and flat

As a bonus we can show you tips for cutting the rainbow sheets into shapes and useful designs using a laser cutter or CNC mill.

Also if you can't find all the colors of the rainbow, you might still be able to source the colors for a specific flag you want to help celebrate! Check all these out here:


  • Source of multi-colored plastic
  • Temperature Controlled Griddle (We used a panini press)
  • non-stick baking sheets (look up "teflon oven liner")


  • Laser cutter or CNC Mill
  • vector designs you want to cut

Step 1: Source Some Plastic

Lots of folks have garbage they want to get rid of, many times you can just ask them! we messaged the 3D printing companies in Panama (Lozury Tech and Mecamaker) who had hundreds of pounds of 3D misprints or bad filament sitting in boxes not knowing what to do with them. We told them we would gladly take the garbage off their hands and turn it into something cool!

You can also hunt around places people dump garbage (like dumps or beaches) and help clean up the environment yourself. I also went into an abandoned recycling center here in Panama that people have just been dumping garbage in anyway, and jackpot! lots of #2 HDPE (milk bottles)

Step 2: Sort the Plastic (and Clean)

The main goal here is to get unique colors out of what will likely be a disorganized mess!

It may seem overwhelming at first, but give yourself some slack and just get 7 buckets ( ROY G BIV) and start sorting stuff like that!

If your plastic is soiled (like old milk jugs), you probably want to give it a rinse in some bleach or something to get any oils off


There are two main things you need to be careful of when sorting the plastic: METAL and BAD PLASTIC

Metal Bits

Even if the people you are getting your plastic from swear that it is sorted, always double check that there aren't secret metal bits stuck inside. Sometimes people make 3D prints with nuts, or other times people clean up a messy workspace and mistake a piece of wire for a piece of filament (both examples shown in the pictures).

The metal is bad because A) it will hurt the teeth of your plastic grinding robot friend) and B) if it gets mixed into your plastics, and you try to laser cut it, the laser won't do anything and you will have parts all stuck together.


if you are sourcing 3D printing plastic, make sure it is sorted by type of plastic. PLA is pretty common and works great for this! ABS used to be more common, but is really gross and fume-y, plus it can be dangerous if you try to laser cut it. AVOID ABS!

Plastic #6 (polystyrene) is also a creeper plastic that will sometimes show up trying to act like it is a nicer thermoplastic. If you melt it is also releases terrible fumes! Avoid #6!

Step 4: Shred the Plastic

Option A: By hand

Get yourself a really big pair of shears, or if you are using a more brittle plastic like PLA, you can get a hammer and smash it up!

Option B: Blender (Plastic Smoothie)

if it is getting annoying doing this manual shredding, you can use this plastic smoothie technique in this video. Basically you can use a normal blender, add some water or rubbing alcohol (evaporates quicker!), and blend up your plastic. (the liquid helps it blend and keeps the plastic from melting into a glob destroying your blender!).

Option C: Industrial Shredder

The most fun and easy option for plastic shredding is of course going big! Here at Dinalab we have been running our own in house-recycling program and have "Terri la trituradora" a nice robot that loves chewing up plastic! You can build one off open-source designs on or you can buy an industrial one like we did online. The term you want to look for is "

plastic granulator" and you can find a shredder for about $1600-$2400 USD free shipping in the USA (getting it to panama was more difficult).

Step 5: Melt It

I recommend using a cheap appliance and melting your plastic outdoors or in an area with lots of ventilation. When properly melting #2 #4 and #5 plastics don't really make any fumes or smells, PLA makes a kind of sweet smell, but mostly you want to avoid breathing in this stuff if you can.

We have used an open face electric skillet before, and it worked fine, it just takes longer. The sandwich press works a lot quicker and more uniformly. It is also much better if you don't have a good shredder for small bits of plastic.

Pour plastic on the sheet

It helps to have a small cup, and pour it on your baking sheet.

Keep a wide margin so your plastic doesn't overflow and spill everywhere.

Put on top sheet and Close the Sandwich Press

I usually put some weights on top to get a good hot smush

Cook the Plastic

We have been experimenting with the plastic to see what gets the best results. If you cook the plastic too hot it burns a bit and gets brittle and crumbly. Also if you cook it too hot, or it takes too long to cool, it can get all bubbly and crumbly too. I think you want to melt it at the lowest temperature that it all becomes nicely liquid, and then cool it very quickly for best results.

So far it seems like for our Panini press and the PLA 350F for 15 minutes does a pretty great job!

Here's our list for other plastics


350F for 20 minutes

#5 (PP)

400F for 8 minutes

#2 (HDPE)

425F for 30 minutes

#4 (LDPE)

425F for 15 minutes

Step 6: Try Out Other Swirls and Patterns!

Go bonkers with the rainbows and have fun! When it melts its gonna get all fun and extra swirly.

Step 7: Cool Under Pressure

After you take the plastic off the heat source, you need to cool it between heavy flat things.

Most of the plastics you might melt can shrink a bit when they cool, so unless you want them to get warpy, you need to keep it squished between things that will hold it flat.

Also if the things you are cooling it with are too insulative, it will take long for the thing to cool, and it will end up all bubbly and fragile (see image).

I use some old ceramic tiles and some weights to help give them a final squeeze. For most plastics a good rule of thumb is to let them cool for as long as you heated them up (so 20 minutes for PLA)

Step 8: Cut Rainbow Objects

You can stop here and have an awesome rainbow colored sheet that you can use as a pride flag or tray or whatever you want. But if you have a device you can program to cut the plastic, like a laser cutter or CNC mill, you can make all kinds of things out of these neat rainbow sheets!

We made some keychains for the upcoming pride parade, a box to hold them in, and decorative Agouti art!

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    1 year ago

    Thanks for sharing.