I collected a bunch of bottle caps from the Clean-up Burley Griffin Day and decided to try another Plastic Experiment with what proved to be mixed plastics i.e. multiple plastic types.

They came from a range of bottles and some were really old. So, I really didn’t know what kinds of plastic they were made of. However, since all of my previous experiments seem to melt fairly consistently, I thought I should try doing something with this plastic too, betting that an old Coke bottle lid would be made of something similar to milk bottles.

But I was wrong. I found that the usual 180C melting temperature for HDPE was only slightly melting most of the other pieces. So, I turned up the temperature and hoped for the best.

Unfortunately, the results were mostly of burned HDPE #2 and half melted other plastic(s) – maybe PP #5. Furthermore, the higher temperatures actually melted the silicon mould too, resulting to it sticking to the melted plastic and destroying my mould.

This Plastic Experiment is a really good example of why recycling plastics is so hard when there are so many variations of plastic with different properties including melting point – creating mixed plastics to be sorted. I still have a few bottle caps left and may try again, but first I have to order a new mould. Sigh…