Milk Jug Clock Disc

Milk Jug Clock

Once upon a thrift store, Sawyer bought a toaster oven.

$15 compression machine, check. Next, a mold.

I was shopping for a small oven, pie pans, and cookie trays at some thrift stores before Christmas. I found just what I had come for, which doesn’t always happen when you’re “thrifting.”

The toaster oven had temperature settings, which was a plus. Plastics have melting temperature ranges specific to their type, and I wanted to take care not to burn the raw material I would use.

But I’m getting ahead of myself. I should note that the main technique of recycling plastic is to shred the waste material into small pieces that can fill a mold and then melt them in that mold. It’s that simple. What’s not as easy, as Precious Plastic has found, is how to do this. They have spent a tremendous amount of energy to design machines that can process plastic waste on small and semi-industrial scales. In fact, they just released the fourth version of their project in early January gratis and under a Creative Commons license so that folks all around the world can mitigate plastic pollution in a local way. CradleCraft is closely modeled after their ideas.

Anyhow, I attempted to replicate a small version of their “compression machine” with the little toaster oven I purchased.

I had a feeling it would work, but I was pleasantly surprised when I held a solid piece of reborn plastic in my hands.

Milk Jug Clock Disc

Here's how I did it. 💡

I saved a couple of yellow milk jugs made of HDPE (Type 2) and used tin snips to cut the sides and bottoms into strips. Then I cut across make flakes around the size I wanted. It took me about an hour and a half to cut up a half liter’s worth of the jugs, which turned out to be about 1.5 jugs altogether. I had to avoid the labels, though, for I couldn’t peel them easily and knew that melting them into the HDPE would downcycle the final product.

Milk Jug Shreddings

Next, I took two identical 18cm pie pans, sandwiched the shreds between them, and stuck them into the toaster oven.

Plastic Shreddings Compression

If I recall correctly, I baked them for about 25 minutes around 150 degrees Celsius. After my timer chimed, I immediately withdrew the pans and compressed them under the weight of a heavy bench.

The cool-down took about 10 minutes, and I pulled out this.

Half Baked Compression

The shreds were beginning to melt into each other, but I could hear creaky noises when I tried bending the piece under slight pressure. I figured that I either needed to let it bake longer or increase the temperature. Since I had read conflicting melting temperature ranges on the web and started low, I opted for turning up the heat.

For another 15-25 minutes, I think I baked the milk jug shreds at 177 degrees Celsius. When I pulled the pans out and compressed them that time, I felt the material give way. And indeed it did, for when it cooled, I retrieved a solid disk of plastic.

I was thrilled! I had watched the folks at Precious Plastic craft a plethora of other products, but it was something magical to discover that I could recycle plastic myself with a small, $15 toaster oven.

It was something magical to discover that I could recycle plastic myself.

Finally, I marked the surface where the clock numbers would go and drilled a hole into the center of the disk. After making a trip to the craft store, I added the numbers with some adhesive before screwing the mechanism into the center. With one AA battery the disk became a clock – our first product.

Recycled Plastic Clock - Our First Product
Sawyer

Sawyer

Author

Sawyer is a maker of things plastic, iron, and digital 3D. After years of discussing sustainable and environmental topics with his family, he founded CradleCraft as a way to creatively steward the plastic resources God entrusts to him.

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