The secrets of ultrasonic cleaning

In the art of cleaning vinyl records, using an ultrasonic system is the preferred method due to its effectiveness and performance. However, it's essential to understand how it works and follow certain rules, especially when using a machine not originally designed for this purpose.

Indeed, machines such as the Humminguru, Degritter, Audio Desk, KL Audio, etc., have been specifically designed to clean vinyl records. Aside from a few available settings, everything is done to achieve the best possible result based on the equipment's characteristics and with complete safety for the record.

This article focuses on ultrasonic cleaning tanks designed for general use but equipped with a device that allows for the installation of multiple discs and their rotation during the cleaning process. These units are generally manufactured in China and may include more or less sophisticated features, but no automation. Those who have invested in this type of equipment must implement the correct method to ensure optimal results.

Principle of ultrasonic cleaning

A bit of theory: This involves emitting a high-frequency sound, on the order of tens of kilohertz, into a liquid medium to induce a phenomenon called cavitation. The waves create cyclical pressure and vacuum fluctuations within the fluid, generating vacuum bubbles. These bubbles then spontaneously implode under the water pressure. This implosion expels a highly localized jet of liquid at high pressure onto the surface to be cleaned, thus dislodging the impurities.

What ultrasound frequency?

There are few options in reality; most cheap bins use a frequency of around 40 kHz, which is sufficient for cleaning vinyl records.

Generally, a higher frequency results in smaller cavitation bubbles, leading to more precise cleaning but also less energy consumption. Conversely, a higher frequency allows for more effective cleaning, but on larger particles, and tends to heat the bath more quickly. It's therefore a matter of compromise!

In any case, avoid very low frequencies (< 40 kHz) which are rather reserved for cleaning coarse mechanical parts.

Bath composition

Use demineralized water, never tap water, which is far too high in minerals. This water will prevent the record from sandblasting and will not leave any mineral residue after drying once the record has been cleaned. Adding a surfactant provides additional effectiveness by increasing the water's fluidity, allowing it to penetrate deeply into the groove (reducing the fluid's surface tension). For this, you can use our Concentrated Vinyl Cleaner , a blend of two types of Tergitol that significantly improves cleaning. This is the product we use at Record Clinic during the Cleaning stage of our Premium process. This high-performance surfactant is highly regarded by archiving professionals and audiophiles due to its very low sonic signature and effectiveness. Rinsing is not necessary if the recommended dosage is followed (2 drops per liter of solution).

You can also add pure isopropanol (IPA) alcohol at 99.9% or higher for its degreasing properties, but in small quantities. We recommend not exceeding 2.5% for safety and effectiveness reasons (a higher concentration does not improve cleaning). Caution: always dilute the surfactant thoroughly in the solution before adding the IPA (risk of lump formation).

Avoid using dishwashing detergent or denatured alcohols that contain other undesirable components such as perfume, dye, glycerin or other fatty products.

Bath preparation

Before the first cleaning cycle, it's essential to degas the cleaning fluid. The goal is to remove all the gases dissolved in the water to improve cleaning efficiency. Some of the ultrasonic energy will be absorbed by the bath itself, reducing its effectiveness on the objects being cleaned. If your device operates at a frequency of 40 kHz, run the degassing process for approximately 20 minutes. At 80 kHz, 5 minutes is sufficient.

If your machine doesn't have this function, wash a batch of discs first and repeat the process. The first pass will degas the bath, and the second will effectively clean your discs. Never run an ultrasonic cleaner when empty!

Cleaning time

There's no need to leave your records in the ultrasonic cleaner for too long: given the characteristics of a vinyl record and the depth of the groove, 2 minutes is enough to remove all contaminants. Longer exposure won't improve the cleaning and will likely cause the bath to overheat unnecessarily.

Since approximately 1/3 of the surface is immersed in the bath (water level below the macaron), a 6-minute cycle will therefore be sufficient to ensure proper cleaning of your vinyl records rotating in your machine.

Rotation speed

If possible, set your motor to the lowest possible speed. Ideally, run your discs once or twice in a 6-minute cycle. By reducing the speed, you decrease the water current (the wake created by the disc moving in the bath) on the disc's surface, which hinders the effectiveness of the ultrasound. This allows the cavitation phenomenon sufficient time to work effectively on the soiled areas. If you own a Vevor, Bpac, or equivalent kit, you can use our speed controller , which will allow you to set the lowest possible speed for your kit.

Separate your discs with the correct distance

This is an important parameter because an ultrasonic cleaner uses pressure waves whose wavelength depends on the frequency. Therefore, when cleaning several discs simultaneously, this spacing must allow for an even distribution of energy on each disc. The ideal spacing appears to be around 20 mm for a tank operating at 40 kHz.

Monitor the bath temperature

Many standard ultrasonic cleaners are equipped with a heating element. While this is very useful for heat-sensitive items to increase cleaning efficiency, excessively hot water is extremely dangerous for your cleaning disc, causing it to warp. Absolutely avoid using this feature!

Never exceed a temperature of 30°C for the bath, otherwise you risk damaging your discs; we recommend a temperature between 25°C and 28°C for safe cleaning.

Change the bath regularly

The particles and other contaminants extracted from the cleaned records remain suspended in the cleaning bath. After a certain number of cycles, this solution will become too concentrated and will significantly reduce cleaning efficiency, or even contaminate your records instead of cleaning them. We recommend changing the solution at most every 8 cycles, but this depends on the number of records being cleaned simultaneously and, above all, on how dirty they are. In any case, you should never clean microgroove records with dirty water! We also advise against reusing a solution after even very fine filtration, as many microparticles will remain suspended, along with grease, soot, tar, and other contaminants in liquid form. Similarly, do not keep your bath for too long, a maximum of 5 to 7 days, as microorganisms (bacteria) will eventually develop.

You are now familiar with the main parameters to follow when cleaning your records yourself using ultrasound. Remember that this technique is only for vinyl records. 78 rpm records and direct-cut records (acetate, Pyral) are very sensitive to humidity, should not be exposed to alcohol, and are fragile; you risk irreparably damaging them.