Last updated on September 6, 2023
Sometimes it is hard to get rid of accumulated dirt particles with traditional cleaning methods. This is when you may need to consider an ultrasonic cleaner that uses ultrasound waves to break the dirt on your jewellery. However, ultrasonic cleaners come with a word of caution as not all gemstones and jewellery can be safely cleaned in them.
How Do Ultrasonic Cleaners Work?
The ultrasonic cleaning process is a scientific innovation that came into use in about 1970. It has been used industrially to clean small intricate parts and accelerate surface treatment processes. Nowadays, ultrasonic cleaners are used to clean various types of objects, such as jewellery, watches, coins, fountain pens, optical lenses, scientific samples, medical instruments, gramophone records, musical instruments, window blinds, electronic equipment and industrial machine parts.
The cleaning process uses high-frequency sound waves, typically 40 kHz, to aggregate the liquid solution and cause the cavitation of solution molecules. The cavitation bubbles transmitted through the liquid help to clean the surface of immersed objects from dust, dirt, oil, grease, wax, pigments, fingerprints and others. The liquid solution can be just water, but a solvent appropriate for the immersed object always enhances the effect.
It is worth mentioning that objects must not be allowed to rest on the bottom of the device during the cleaning process. This will prevent cavitation from taking place on the parts of the object, not in contact with the liquid solution.
The ultrasonic cleaning process lasts between three and six minutes but can be exceeded depending on the object that has to be cleaned. It should also be noted that ultrasonic cleaning by itself does not sterilize objects. That is why in medical applications, cleaning is typically followed by the sterilization process.
What Gemstones Can Be Cleaned with an Ultrasonic Cleaner?
Ultrasonic cleaners are compatible with some non-organic gemstones and precious metals. However, there are some gemstones and jewellery that should not be cleaned in ultrasonic machines.
Diamond is the hardest and most durable gemstone, 10 on the Mohs hardness scale, meaning it can easily withstand ultrasonic waves. However, sometimes it can be risky to clean diamonds with an ultrasonic machine. This is especially true for diamonds with a significant amount of inclusions, as ultrasonic vibrations can affect the internal flaws and crack the stone. If this is the case, it is better to opt for professional cleaning.
Another risk group is clarity-enhanced diamonds. Clarity enhancement is made through laser drilling and fracture filling, meaning the crystal structure of a stone gets damaged during the enhancement process. This makes an enhanced diamond more likely to crack or even break when cleaned with an ultrasonic device.
Similarly, do not use an ultrasonic to clean colour-enhanced diamonds. If the diamond has been treated to enhance its colour, depending on the type of treatment, ultrasonic vibrations can undo this effect making the colour of the stone less vivid.
As a general rule, the less durable the gemstone, the more it is prone to damage in an ultrasonic cleaner.
The gems that have been filled or coated with oil, resin or wax should not be cleaned in an ultrasonic device. Such treatments are not permanent and can be damaged or removed during the cleaning process. Coating and filling are used on emeralds, lapis lazuli, malachites and opals.
Avoid ultrasonic cleaners if gemstones have been treated by heat to enhance their colour. While transparent ruby and sapphire are somewhat safe to clean with an ultrasonic, star ruby and star sapphire should never be cleaned in the machine.
The gemstones that are sensitive to heat and high temperature changes should not be cleaned by ultrasound as well. Some of these gems include tanzanite, topaz, moonstone, malachite, lapis lazuli, bloodstone, turquoise, zircon and others.
As you can see, many non-organic gemstones are not suitable for ultrasonic cleaning. Instead, you can use gentle cleaning solutions or just warm soapy water to make them clean again.
Organic gemstones, such as pearl, mother of pearl, coral, amber, ivory and jet, are very soft and porous. They should never be put into an ultrasonic cleaner because organic gemstones can easily get dissolved by heat and vibrations. The best way to clean them is to use warm soapy water.
What Metals Can Go in an Ultrasonic Cleaner?
Ultrasonic cleaners are known for working great with precious metals. You can safely clean white, yellow and rose gold using ultrasonic devices. Silver and platinum jewellery can also be cleaned in an ultrasonic machine. The exception is tungsten, as it is prone to damage when subjected to ultrasound waves.
Ultrasonic cleaners are not recommended to use on metals that are oxidized or antique. In such a case, you can use gentle cleaning solutions or warm soapy water.
As a general rule, when purchasing any jewellery, ask the jeweller if it can be cleaned with an ultrasonic cleaner. The best practice is to make sure the jewellery does not contain alloys or gems that may become vulnerable during the cleaning process.
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