Wednesday, January 2, 2019


Belladonna was looking at new cases for her new phone.

It came down to either black or clear. Then she asked my opinion.

Thinking back to my days in automotive engineering, I told her that the clear plastic was much less likely to be degraded with "regrind".

Short-shots, scrap, gates-and-sprues, parts with poor surface finish are ground back up and rerun. Injection molding is a bit like balony. Nothing is wasted.

Darker colors hide better. I suppose manufacturers could segregate by color and put clear scrap into hoppers of clear pellets and ivory parts into ivory pellets and so on. But it is simpler to just throw them all into the darkest color that the plant runs. It hides.

For items like automotive trim, there was a 25% maximum on the amount of regrind that could be added. Each time the plastic was ground and reheated additional damage was done to the base polymer. When we had issues with plastic trim breakage it was always the darkest colors. Go figure.

I asked Bella if she intended to leave her phone out in the sun. Pigment does offer UV protection.

Bella responded that she intended to keep it in her pocket.

She got the clear.


  1. Makes sense. And I've heard that before, which is why I DON'T buy vehicles with a dark interior (and I live in Texas)... LOL

  2. Always interesting when you share your automotive/production knowledge.


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