The Thirteenth Hour Podcast #285: Recycling LDPE and PP Plastic into Plastic Synths!

This week’s episode continues from the last three week’s crafting episodes … but instead of HDPE (high density polyethylene, a.k.a. #2) plastic (which worked pretty well, as described in last episode), this time, I’m experimenting with LDPE (low density polyethylene, a.k.a. #4) cut from a lid top (instead of Perler beads which I used last time) as well as PP (polypropylene, a.k.a. #5) plastic to do essentially the same thing as last week.  Again, I was not sure this would work. 

Just like the last few weeks, I’m using the silicone molds I used to make Logan’s synthesizer (watch for more stop motion animation music videos with him soon!):

For this project, I’m again using cut up strips of #4 and #5 plastic.  Here are the cut up bits of #4 plastic in the synth mold getting heated up with a heat gun.   As mentioned last week, heating plastic leads to fumes, so it would be a good idea to do this with some eye and mouth protection (safety goggles, a mask) in a well ventilated area, like a garage or outdoors.  I wouldn’t do this in your kitchen oven!  A pair of winter gloves are great for protecting your hands.


Like HDPE, both LDPE and PP gets viscous and gooey when heated.  PP took longer and did not take to the mold as well.  With both of these, if you touch it or try to tamp it down too soon, it gets everywhere, just like hot tar.  It’s pretty easy to scrape off a smooth surface later, but I found I needed to wait longer than HDPE for it to become workable (PP – the longest).  As before, you will probably need to add additional plastic, heat that, and repeat the process until you fill the mold, like below.  I think I had to add 4-5 layers of plastic strips until I filled the mold.



Here are the LDPE synth (red) and the PP synth (white) when they were just taken out of the mold the first time.  If you look closely at the details, you can see some of the strands did not liquefy.  So I heated the synth sides, flipped them back into the molds, pressed down, and … you can see the results below.


The PP synth worked okay – kind of rough, but it did work.  Here it is next to the the lid it once was.  It took a whole lid to make the synth.


Here are the different synths according to plastic type, in order of ease of use, from bottom to top.   There you have it, recycled plastic toys!


And, as mentioned in the episode, the patches I mentioned a few weeks ago are now ready and available for purchase here!  They come with a high quality mp3 download from Once Upon a Dream, the next Thirteenth Hour soundtrack LP.


If you still have a cassette player, take advantage of the following deal and be transported to another world!  SALE!  While supplies last, grab Long Ago Not So Far Away on cassette!  Just $1/tape!




There are now Thirteenth Hour toys!  If you’d like to pick up one of these glow in the dark figures for yourself, feel free to email me or go to the Etsy store I set up ( and get them there.

If the past few months have got you needing a break, you may want to chill out to this 80s synth throwback track for a upcoming LP with the accompanying music video:

Empty Hands, the synth EP soundtrack to the novella, Empty Hands, is now out for streaming on Bandcamp.  

empty hands ep cover_edited-2.jpg

Stay tuned.  Follow along on Spotify!  There is also a growing extended Thirteenth Hour playlist on Spotify with a growing number of retro 80s songs.

Check it out!

As always, thanks for listening!


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