@allen.wrench, the 70% dilute stuff you get at the pharmacy is not identical as the IPA you use at work. Both are 2-propanol (e.g. isopropyl alcohol or isopropanol) but by mixing it with water the cosmetic stuff holds fat and oil in solution and makes it somewhat gentler on your skin. This serves to make it considerably less effective at cleaning and will help the grease and oil spread, like, well, oil on water. This is sort of like comparing nail polish remover and true acetone. The stuff they add to polish remover to make it not eat your skin as badly and smell so much reduce it's effectiveness as a solvent in the shop.
The IPA you see on work benches is 99% and works better. But it does require you use lots of clean rags since lacking the water all the IPA does is dissolve stuff and would just leave it sitting there otherwise. As a point of comparison the spray IPA CRC sells is also 70% IPA but the 30% is HFC-152, which is the areosol propellent so it's not diluted on the work surface.
Most non-chlorinated brake cleaner is mostly acetone, which is just IPA that's been oxidized. Or in reverse you can make acetone into IPA by hydrogenation. If you look on the MSDS sheets for non-chlorinated brake cleaner you'll usually see it's acetone and CO2. I wonder if the CO2 is chosen chemically to dehydrogenate as well as propellant. Dunno on that.
Just my $0.02 but I switched to non-chlorinated cleaner years ago because I don't like breathing VOCs and wearing a respirator all the time using the chlorinated stuff. I don't like losing the choice but I haven't used old brake cleaner in years anyway so on the ground it's not a big deal for me. Should say here, too, that even non-chlorinated isn't exactly healthy and the brake dust isn't good either. But I'm old enough to remember when you had to worry about both brake cleaner and asbestos in the friction material. It's truly amazing any of us lived past 27.
So IPA or acetone, it's 6 of one, half dozen of the other. Both work at the task, choose on convenience and cost. I rather like the idea of bulk IPA and spray bottles. My experience with those chemical resistant sprayer is mixed though. I'll be watching how that works out for you Allen.
Fun fact, they normally use tetrachloroethylene in regular brake cleaner. That's also what is used as dry cleaning fluid. Being a chlorinated organic when you expose it to heat and UV you can reform into phosgene.
en.wikipedia.org
This is something that crosses over perhaps because people who weld know you need to clean, clean, clean some more. Someone years ago had a light bulb go off and used brake cleaner to degrease their work. The old chlorinated stuff killed them. You need to use a non-chlorinated chemical that flashes quickly and completely like IPA or acetone to clean your work, so
non-chlorinated brake cleaner is a pretty good pre-weld cleaner. That's another reason I switched. Just one chemical around in bulk that can do a few things equally mediocre.
