Sunday, March 22, 2020

Don't use 95% Ethanol for cleaning PVC

In unfortunate haste, I tried to clean some of the smell of the big plastic topped rotary encoder knob on my newly acquired HP 3582A Spectrum Analyzer (a standard in audio analysis).  Sniffing around the instrument, much of the smell seemed to be coming from this knob, possibly because of it's flat plastic surface being a sponge for odors like cigarette smoke.

I used Everclear (95% ethanol) and Q tips.  Fairly quickly it started creating streaks and even sandpaper like bumps in the PVC surface.  (It didn't do much for the smell either.)

I vaguely remembered many years ago hearing some electronics maven (probably an old tech at a surplus store) tell me that 91% Isopropyl was safer to use on plastic than 95% ethanol.

But quickly scanning through expert opinions on various sites, I was not finding anyone distinguishing the properties of ethanol and isopropyl on PVC.   Both could be used briefly but longer would cause streaking, read a typical opinion.

Finally, I found this authoritative table, which indeed shows that isopropyl is safer on PVC.  Ethanol is the WORST of the simple alcohols, gets a C rating.  Isopropyl is among the best of the alcohols, gets an A1 rating.  Butanol is A2.

https://www.calpaclab.com/pvc-polyvinyl-chloride-chemical-compatibility-chart/

I'm actually thinking the Pledge floor cleaner, designed for vinyl floors and based on Butanol and surfactants, might be the safest and effective.  It's supposed to be diluted 1/64-1/32 also, fwiw, which makes the Butanol very dilute.

Some pledge polish for hard surfaces (put on a cloth first) seemed to remove the smell and replace it with nice lemony scent.  But the lemony scent wore off and the original smell returned.








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