Some rather wordy note on my experiences with ultrasonic baths.
About twenty years ago, small inexpensive ultrasonic baths started to appear, which made impressive claims about their cleaning capabilities. On impulse, I bought one for a tenner from Lidl – it went back for a refund the same day – useless for anything other than maybe cleaning a pair of earrings or such like. They cut out after three minutes, and the cavitation action is barely visible, with little in the way of an audible ‘fizz’ which arises from effective cavitation.
Having not learned from that experience I bought a so-called ‘professional’ bath from Maplin, the electronic gimmickry store that was, thinking that one might be better. It wasn’t, so it too went back. The problem with such cheapo baths is that while they may oscillate at ultrasonic frequencies, (generally 40 kHz) they don’t do so with sufficient amplitude to be effective – typically 20 - 30 Watts, and most have a maximum cut-off time of 3 to 4 minutes. I don't think they achieve anything that couldn't be achieved just as quickly and probably more effectively, with a toothbrush and detergent. That said, there are those who claim that they do an adequate job. A good test of effectiveness is to hold a piece of aluminium foil in the fluid and if pinholes don't appear in the foil within minutes, it's just a toy, which is all that most small baths for domestic use are.
Commercial/industrial ones tend to be from 70 Watts upwards, from about 2 Litres upwards in volume, and have a built-in heater, thermostat, and timer.
I continued to hanker after an effective bath and towards the end of 2012, I learned of Allendale Electronics, who supply professional small ultrasonic baths as used in hospitals, dental practices, GP practices, vets, laboratories, tattoo studios, jewellers, watch repairers, acupuncturists etc. A 2 Litre one to suit my needs was just over £100 back then – not cheap, but not expensive for what it does and how well it’s made. The ultrasonic power (at a frequency of 40 kHz) emitted by the transducer to the bath is 70 Watts, and it has 60-Watt thermostatic heater which is pre-settable up to 80 C. It has a built-in timer for up to 80 minutes, and all the settings are displayed on a digital display.
The model that I bought has since been superseded with a similar one but with additional features, such as ‘De-gas mode’ - used after a fluid change to rapidly remove air from the fluid so it can provide maximum cleaning effectiveness from the start of the cleaning cycle; ’Delicate mode’ - the cleaner runs at half power which provides a less aggressive cleaning action for fragile/delicate items, and ‘Full-power’ mode - a powerful deep clean that will clean heavily contaminated items.
Almost all ultrasonic baths are marketed on their (alleged!) liquid capacity - for example, 600mL, 1 Litre, 2 Litre and so on. A chum bought one which was described as '2 Litre'. He thought it looked too small to be of 2 Litre capacity, so he filled it with water up to the fill line and found that it contained only a little over 1 Litre. (It went back for a refund).
Out of curiosity, I decided to check the volume of my Allendale ‘2 Litre’ one.
The dimensions of the tank at the top are: 15cm x 14cm & 10cm deep. In describing the tank as '2 Litres' they appear to have simply multiplied those dimensions, which would equate to 2,100 CC. However, the inner corners of the tank are rounded, and the sides slope. There is a fill line which is 3cms below the top of the tank - all factors which reduces the capacity of the tank. When filled to the brim, the tank holds just 1.8 Litres, but when filled to the fill line, holds just 1.4 Litres. In Apart from it's inaccurate and misleading description, what really matters is the size of the wire basket into which items for cleaning are placed, as that further reduces the capacity. In mine, with the basket in place, it is 14 x 12cms at the top, and 7cms high to the fill line. Hence, the physical capacity of the basket in 1,176 CCs - about half that of the claimed capacity of the tank.
Really, the key point to bear in mind if thinking of buying an ultrasonic cleaner, is whether the basket capacity is large enough to contain whatever items you may need to place in it for cleaning. In my case, most of the items I've used it to clean are so small that they'd fall through the mesh of the basket so I put them in a small glass jar immersed in the liquid. (A basket is necessary to avoid damage to the tank, and has to be bought as an extra.). I use mine for cleaning small brass, aluminium and steel parts and knobs of vintage radio which I restore as a hobby.
Here's a 2 Litre 50W ultrasonic power, 100-Watts heating. £112.69 inc VAT:
2 Litre Digital Ultrasonic Cleaner Cavitek Professional 100W
3 Litre 100W ultrasonic power, 100-Watt heater. £149.96:
3 Litre Digital Ultrasonic Cleaner 100W
Hope that might be of interest when considering the pitfalls and in deciding what size of bath to buy.
