Ultrasonic cleaning: how it works, what it cleans and the machine you need

What the cavitation bubbles do

A transducer under the tank floor turns electrical power into vibration at 25 to 45 kHz. That vibration stretches and squeezes the liquid thousands of times a second.

On the stretch, the liquid tears and a tiny vacuum bubble forms. On the squeeze, the bubble collapses. It collapses hardest where it meets a solid surface, and the jet it throws out knocks the dirt loose. There are millions of these cavitation bubbles in a running tank, all collapsing against every face the liquid touches at once. The solution then holds the dirt in suspension so it does not settle back.

Three things set how well it cleans: the power going into the tank for each litre of liquid, the temperature, and the solution. Heat matters because most soils soften between 50 and 70 °C. Frequency matters less than people think: 40 kHz is gentler and suits small and delicate parts, 25 to 28 kHz hits harder and suits carbon, baked oil and heavy castings. The MSX 30 switches between the two.

What ultrasonic cleaning does well, and what it will not do

It is a surface process. If the liquid can reach the dirt and the right solution can loosen it, the cavitation bubbles will take it off.

The cavitation bubbles do the scrubbing. The solution decides what comes off.

Water on its own cleans dust. For anything oily you need a few per cent of a concentrate that wets the soil and holds it in suspension. Pick it by the dirt and by the metal, and keep to the dose: more concentrate does not clean faster, it only leaves residue.

Never put petrol, thinners, acetone or any flammable solvent in an ultrasonic tank. The heat and the cavitation bubbles throw vapour off the surface.

Be honest about the job before you spend the money

If you want to clean a ring, a pair of glasses or a watch band a few times a year, and your budget is under $1,000, a small tank from Vevor or an online marketplace will do that job. They are not a Misonics machine and they are not meant to be. For a one-off home job they are the better bet, and we would rather tell you that than sell you a bath you do not need.

Whatever tank you buy, the solution decides what comes off. A small machine run on water or dish soap disappoints; the same machine run on a concentrate formulated for ultrasonics and for the part in front of you is a different tool. For the home mechanic, bike or kart builder, FX Degreaser at 15% in water for oily engine parts comes in a 10 L pack for $132 inc GST, and that pack makes about 65 L of bath, or ten fills of a 6 L tank. For aluminium carburettors, castings and anything you want to come out bright, AquaVantage 815 GD is the step up, 10 L for $242 inc GST. Yes, the solution can cost more than a cheap tank. It is also the part that does the cleaning. Jewellers and watch repairers: ask us about a jewellery cleaning solution in small packs.

The picture changes the moment the tank goes into a workshop, a lab, a clinic or a plant and runs every day. Then four things decide whether it keeps cleaning in a year's time, and they are the four things the price pays for.

Quality costs money. For a commercial or industrial buyer it costs less than the machine that stops, the parts that come back dirty and the technician standing beside a tank that will not reach temperature. Before you buy anything, from anyone, check the power density in watts per litre of tank volume, whether the frequency sweeps, the basket size against your largest part, and who holds the warranty.

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