Clear plastic clam shells from take out, sushi container tips and other #6 plastic which isn't always accepted by your local recycling service can be colored, cut and shrunk in the oven to make pendants, guitar pics, accessories, ornaments, etc!
Step 1: Pick an Image
Since you are working with trash there are many variables that can distort your results. For example cutting out a circle will result in an oval because the plastic shrinks at different rates along each axis. So collect enough bits and expect happy accidents, as you practice you'll get used to the shortcomings and be able to use them to your advantage.
The plastic will shrink by about 50% so choose an image twice as big as you want the final to be. Print it out and you can trace it below the plastic.
Or, do a free form geometric design, or doodles. You can use sharpies which will result in transparent colors. You can also use opaque permanent markers that are metallic. I haven't tried paint pens yet.
You'll also need cotton balls and rubbing alcohol to clean the plastic and super fine sand paper or Emory boards from your nail polish kit. And a toaster oven, preheated to 215 degrees.
Step 2: Sand It
Rough up one side of the plastic a bit with a soft Emory board or 300+ grit sanding sponge. This will help your marks stay where you put them and be less likely to smudge. You can leave the other side shiny. Wipe with cotton ball dipped in rubbing alcohol.
Step 3: Draw/Trace
Draw or trace a printed image. You can use cotton balls or swabs as an eraser. Since it's clear, if you are using opaque pens/markers you will see the colors you put down first on the other side. If you layer opaque colors over each other, the top colors are only seen on one side, and will be sorta dull when finished.
Step 4: Cut and Punch Holes!
Trim neatly which is a little tough since this plastic is kinda brittle. You can sand the edges so they aren't sharp and give angles a trim.
Don't forget to punch holes! That's the only way you can make jewelry, key chains, anything but glue them to something. I use a 1/8" hole punch for tiny holes. Punch the holes no closer than 1/8" from the edge. Further in may require a larger jump ring. You can also use a standard hole punch.
Step 5: Cook
Preheat toaster oven to 215 degrees. I put mine on aluminum foil but you can also use parchment paper. Place them on the pan and into the oven and watch them. It will take about 30 seconds. They will flip and curl and usually go back kinda flat. Take the pan out and I use chopsticks to make them flat if they are too curly or bumpy.
Step 6: Sand and Finish
Sand the edges again because they are now much thicker than before. Try to avoid sanding the image.
Use the holes to make jewelry or whatever! Please excuse my horrible wire working on these I just wanted to show an example and also not loose them because they are small.
The photo shows one with the colored side up and the other with the clear side up.