Acetone Or Xylene ?

Conductivity, that's what labs use. Highly purified water has a resistance of about 18 MOhm, it's nearly non-electroconductive. Most of the conductivity of water is due to dissolved impurities and gases - which are removed during purification.

As far as the need to test for use on coins - that's a non-factor. The widely available distilled or deionized water is good enough and I'm sure those manufacturers continuously monitor the conductivity of their products as it will tell them if there's a production problem.

A little off topic but also NEVER microwave distilled water as it does not boil due to the lack of impurities. If distilled water is super heated and you add something to it it will explode and burn everything within range

Thanks for all the good information. At $1 a gallon, I can buy my distilled water - just won't use it for my instant coffee.

You know I intentionally left that part out for you to do right jbuck

Be careful with using acetone when handling mint state bronze or copper... photochemical reactions can occur between the two (in the presence of water vapour), which can leave a "gasoline-on-water effect on the lustre"

http://www.sciencedirect.com/scienc...468601003590

I use Toluene for working with mint state bronze and copper.

Is it particularly harmful to slightly breathe in acetone vapors briefly while checking the coins?

Thanks conder. I can feel.a very faint burn when I switch em or sit there for a few seconds trying to hold my breath while toothpicking

Good thing I prefer my copper in brown.