Ultrasonic cleaning

Just be careful if your wife asks you to clean her rings !!

Some precious stones have been know to be damaged by ultrasonics so I am led to believe.

Phil

Thanks Michael, I'll be keeping it for now...

Just found the manufacturer's website BTW - seems new ones are expensive! There's also a downloads page which includes a PDF on periodic testing of ultrasonic cleaners. Sadly the pages are not in order, but it does describe the 'foil ablation test' in some detail, with some pictures of what to expect, alongside some other tests more relevant to medical use.

A few comments on recent posts:

"Russell, is your cheap Aldi unit as noiticeably active as this - I'm wondering if yours is a bit of a dud, or if I could achieve even better results with a proper unit."

I think my Aldi unit may have deteriorated with age. It is supposed to produce 50 W of ultrasonic power yet I have measured it's power input and it only consumes 40 W so I doubt if it would be producing mre than 20 W. Small items put in it do jiggle about a bit.

"A lot of people have un-realistic expectations of what these machines actually do, they seem to expect a grubby old casting to come out nice and shiny. This is not going to happen."

It depends very much on what cleaning fluid you use. The castings shown in Neil's article were cleaned using Allendale's Oxidation and Rust Removal solution. That is a 10 to 20% solution of citric acid so 1 or 2% after dilution - a rather expensive way to buy citric acid but effective.

"if you are cleaning brass parts you can get good results using one of the ammonia based clock cleaning solutions, this will brighten the brass as well as removing dirt"

Agreed, I have used Horoclean in the past, a mixture of ammonia solution with various organic solvents. For some reason it can't be exported.

"Optics can also be cleaned but again a short immersion time."

I would be a bit concerned about coated lenses having seen paint removed from metals. Have you tried it Clive?

"Some precious stones have been know to be damaged by ultrasonics so I am led to believe."

Yes, don't put pearls or opals in the bath. Any stones with cracks are liable to be damaged, especially emeralds. There should be no problem with other gemstones.

As an aside, I have found that washing up liquid isn't very good as it foams too much. Many American sites recommend using Simple Green whatever that is but I have a 5 litre container of detergent sold by Lidl for use with pressure washers and that works very well - add a dash of ammonia for use with brass.

Russell.

My use of the ultrasonic with optics is where there is oil that has gone into a prism mount and the prism is glued in place. A few seconds in the ultrasonic does clean out the oil. We in the instrument trade use Ether on small stick that have Chamois leather glued to the ends. This allows delicate cleaning into corners and close into edges of lens. Do not flood with ether as it will attack balsam and optical cements,. I have not seen it attack optical coatings though i am sure prolonged immersion would affect it. Fungus is the optical coating killer. For that we use Hydrogen Peroxide at 6 to 9 % rubbed on with a cotton bud.

We always did a degrease bath and scrub in white spirit first and a wash off in detergent and then into the ultrasonic. Do not let the white spirit into the ultrasonic fluid.

Clive

In response to Bikepete I picked the same model up at a car boot sale. The seller had emptied a tin of soup into it and was complaining that it wasn,t getting warm. I offered a fiver and got it including a basket, I sent it back to Walkers for a check up. I am more than pleased with it. Though I have had the pallets and impulse pin come free in a platform escapement I was using windscreen washer fluid

Roy

Edited By roy entwistle on 02/10/2016 22:10:59

For the record the unit I used made a loud hissing/rushing sound - quite high pitched and you wouldn't want to be trying to concentrate while in the same room as it. It didn't upset the dogs, but they did look at me in a funny way whenever I switched it on.

I would guess a unit that just buzzes isn't as strong. The Allendale one has three modes full wave, half wave for 'gentler action' and 'degas'.

Neil

The purpose of these modes is a little confusing for me. The transducers in these units are piezo ceramic devices attached to a horn to couple them to the tank. They are resonant at about 40 kHz with a high Q factor and are driven by a relaxation oscillator which uses the transducers as the main frequency determining components. So the output of the transducer will be a sine wave with some harmonics. It can't be full or half wave.

The power supply for the oscillator is usually a poorly smoothed rectified sine wave using a bridge (full wave) rectifier. Perhaps by half wave they mean that the rectifier is replaced by a half wave rectifier. This won't change the output waveform but will pulse it with a 50:50 duty cycle, halving the output power. Yet the Allendale unit has a power setting so why bother?

Degassing is done by heating the water and running the unit for about ten minutes so the degas mode seems to be unnecessary as well.

Does the manual give any explanation of these modes?

Russell