The secrets of ultrasonic cleaning

In the art of vinyl cleaning, the use of an ultrasonic system is the preferred method due to its efficiency and performance. However, it is still necessary to understand how it works and to follow a few rules, especially when using a machine not originally designed for this purpose.

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

The purpose of this article concerns ultrasonic cleaning tanks designed for general use but equipped with a device for installing multiple records and ensuring their rotation during the cleaning process. These devices are very generally manufactured in China and can integrate more or less sophisticated functions but no automatism. It is up to the user who has invested in this type of equipment to implement the right method to ensure optimal results.

Principle of ultrasonic cleaning

A little theory: It involves diffusing a high frequency of several tens of kilohertz into a liquid medium to cause a phenomenon called cavitation. The waves will cause cyclic pressures and depressions in the fluid, thus generating vacuum bubbles. These bubbles then spontaneously implode under the pressure of the water. It is this implosion that will expel a highly localized, high-pressure jet of liquid onto the surface to be cleaned, thereby dislodging impurities.

What ultrasonic frequency?

In reality, there are few choices; most inexpensive tanks use a frequency of approximately 40 kHz, which is sufficient for cleaning vinyl records.

Overall, the higher the frequency, the smaller the cavitation bubbles will be, resulting in precise but also less energetic cleaning. The inverse allows for more effective action, but on larger particles, and tends to heat the bath more quickly. It's therefore a matter of compromise!

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

Bath composition

Use demineralized water, never tap water, which is much too rich in minerals. This water will prevent the sandblasting effect on the record and will not leave mineral deposits during drying once the record is cleaned. The addition of a surfactant provides additional effectiveness by increasing the fluidity of the water, i.e., by allowing the water to penetrate deeply into the groove (reducing the surface tension of the fluid). For this purpose, you can use our product Concentrated Vinyl Cleaner, which is a blend of two types of Tergitol that significantly improves cleaning. This is the product we use at Record Clinic during the cleaning step of our Premium process. This powerful surfactant is favored by archiving professionals and audiophiles due to its very low sonic signature and effectiveness. Rinsing is not necessary if the recommended dosage is respected (2 drops per liter of solution).

You can also add pure alcohol such as 99% Isopropanol (IPA) for its degreasing properties, but in modest proportions. We recommend not exceeding 2.5% for safety and effectiveness reasons (a higher rate does not improve cleaning). Be careful to always dilute the surfactant in the solution thoroughly before adding IPA (risk of "clump" formation).

Avoid using dish soap or modified alcohols that contain other undesirable components such as perfume, dye, glycerin, or other greasy products.

Preparing the bath

Before proceeding with the first cleaning, it is essential to degas the cleaning fluid. The idea is to remove all dissolved gases from the water to improve cleaning efficiency. Indeed, part of the ultrasonic energy will be absorbed by the bath itself, reducing its action on the objects to be cleaned. If your device operates at a frequency of 40kHz, start degassing for about 20 minutes. At 80kHz, 5 minutes are sufficient.

If your device does not have this function, clean a first batch of records and repeat a second time. The first pass will degas the bath, and the second will allow for effective cleaning of your records. Never run an ultrasonic machine empty (i.e., without water)!

Cleaning duration

It is not necessary to leave your records in your ultrasonic tank for too long: given the characteristics of a vinyl record and the depth of the groove, 2 minutes are sufficient to remove all contaminants. A longer exposure will not improve cleaning and risks heating the bath unnecessarily.

Given that approximately 1/3 of the surface is immersed in the bath (water level below the label), a 6-minute cycle (regardless of the tank's frequency) will therefore be sufficient to ensure proper cleaning of your rotating vinyl records in your machine. The most important thing to ensure homogeneous cleaning is to make sure your records have completed a full number of rotations over the programmed duration, of course.

Rotation speed

If possible, set your motor to the lowest possible speed. Ideally, your records should rotate once or twice over a 6-minute cycle. By reducing the speed, you reduce the water current (wake caused by the record moving in the bath) on the surface of the record, which harms the effectiveness of the ultrasound. This will allow time for the cavitation phenomenon 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 on your kit.

Separate your records with the right distance

This is an important parameter because an ultrasonic machine uses pressure waves whose wavelength depends on the frequency. When cleaning several records simultaneously, the spacing must allow for an identical distribution of energy on each object. The ideal spacing seems to be about 20mm between each record for a tank operating at 40 kHz. 

Monitor the bath temperature

Many standard ultrasonic tanks are equipped with a heating mechanism. While very useful for heat-insensitive objects to increase cleaning efficiency, water that is too hot is absolutely dangerous for your record, causing warping. Absolutely avoid using this device!

The bath temperature should never exceed 30°C to avoid damage to your records; we recommend a temperature between 25°C and 28°C for risk-free cleaning.

Change the bath regularly

Particles and other contaminants extracted from cleaned records remain suspended in the cleaning bath. After a certain number of cycles, this solution will be too concentrated and will significantly reduce cleaning efficiency, or even contaminate your records instead of making them clean. We recommend renewing the solution as soon as your bath is no longer translucent. Cloudy water is a sign of a large number of suspended particles, which must therefore be discarded. In any case, you don't clean microgroove records with dirty water! We also do not recommend reusing a solution after even very fine filtration because many microparticles will remain in suspension, as well as fats, soot, tars, and other contaminants in liquid form. Similarly, do not keep your bath for too long, a maximum of 5/7 days, as microorganisms (bacteria) will eventually develop in it.

You are now aware of the main parameters to follow for cleaning your records yourself using ultrasonics. Remember that this technique is reserved for vinyl records. 78s and direct-cut records (Acetates, Pyral) are very sensitive to humidity, should not be exposed to alcohol, and are fragile, so you risk destroying them irreparably.