What percentage alcohol is used?

usually 99%

99%. 70% if I'm doing parts disinfection for medical devices.

I totally agree though my use of it is pretty different ;)

I'd be very scared of IPA in an ultrasonic cleaner. Sounds like a recipe for a fire. Or is your machine perhaps designed for safe IPA cleaning?

A few companies do make ultrasonic cleaners that are designed for flammable solvents, but they aren't common.

The easiest option is to just fill a plastic food bag with solvent, throw your part in, seal it with a clip and float it in your ultrasonic bath. The bag contains the vapour for safety, and it's easy to switch between different solvents and solutions.

That's a quite elegant solution I hadn't considered before.

That is next generation sous vide. Just controlling temperature is ho-hum. Getting it to just the right ultrasonic vibration to "cross-modulate the adipose frequency" is next level.

And someone is already doing it:

https://besservacuum.com/en/ultrasonic-food-treatment-machin...

I've used both EtOH and propan-2-ol (IPA) for decades in ultrasonic cleaners both at room temperature and heated (quite warm to feel but not boiling hot) and never had a problem with fire.

I'm scrolling before coffee and initially took your acronym as India Pale Ale, which would certainly be a different cleaning experience...

Do ultrasonic cleaners get hot?

I've run isopropyl alcohol in an ultrasonic cleaner.

It did get significantly hot after a while. And smelly, so it was surely aerosoling (is that a word?) somewhat.

I did it outdoors and away from anything that could catch fire because it felt rightly sketchy.

It's basically an industrial ultrasonic humidifier attached to the bottom of a buffet tray. And it does get warm.

Typically not (though some have heaters you can apply) but they atomize the fluid pretty well. The tiniest spark (static electricity) and some bad luck and you have the lid shooting into the roof and then a fire. As with everything, if you know what you are doing, go ahead.

A lot of ultrasonic cleaners have a heating element.

The machine doesn't get hotter than 50C. IPA isnt igniting at that temp.

Even more spicy is vapor phase cleaning... evaporate the solvent, condense on the part to be cleaned suspended above it. Very effective since the impurities are constantly distilled out.

Also kinda explody.