An Introduction to the Ultrasonic Cleaning of Vinyl Records

Here at CleanerVinyl we often get the question "how does ultrasonic cleaning work", and what makes the process different from the classic record cleaning methods that use a special cleaning fluid in combination with brushes and/or vacuum wands.

Ultrasonic vinyl record cleaning is a very different approach compared to these classic methods. There is no mechanical interaction between a cleaning tool and the vinyl surface, which means no micro-scratches are introduced by the cleaning process. Brushes, pads and wands essentially remove dirt by scratching along the surface scraping away any dirt that is in their path.

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The ultrasonic process has a bit of a 'magical' aspect to it. One simply submerges the to be cleaned item (your vinyl records!) in the cleaning fluid (usually water with a bit of detergent or surfactant), turns the cleaner on and then the items get clean without any further interaction. 

The secret to this process is the formation of small evacuated bubbles in the water due to the interaction with the ultrasound that is transducer into the water. Piezo-electric ultrasonic transducers vibrate the bottom of the tank at 40 kHz or similar. This introduces sound waves into the fluid in the tank. Like in sound waves in the air, this introduces high and low pressure regions that travel through the tank. In the low pressure regions small evacuated bubbles form. These bubbles move randomly in the tank until they collapse ("cavitate"). This cavitation occurs predominantly in the vicinity of a surface. This is shown in the first Figure, which shows a series of high speed camera photos at 305000 frames/sec of a cavitating bubble in front of a surface.

Fig. from: E.A. Neppiras: "Accoustic Cavitation", Physics Reports 61(3), pp.159-251, 1980.

The photos show that an energetic water jet directed towards the surface is formed during the cavitation. This jet blasts away dirt particles attached to the surface. This is the main cleaning action of the ultrasonic process.

Here is another pretty picture of such a bubble with a more 3 dimensional view:

Fig. from: “Fundamentals and Applications of Ultrasonic Waves” by J. David N. Cheeke

The random movement of the bubbles before cavitation as well as the 'automatic self-alignment' of the water jets towards surfaces immersed in the cleaning fluid is the reason that the cleaning process works wherever the cleaning fluid can penetrate, even in difficult to reach nooks and crannies. This is impressively shown in the video below, where it is demonstrated that an ultrasonic cleaner can remove dirt between two pressed together ceramic rings. This implies that there is not much concern about 'perfect spacing' of the records, or the orientation of the records relative to the transducers. It basically works wherever the fluid can penetrate.