I just came upon this thread so I figured I would provide my experience with ultrasonic cleaning of vinyl records.
I studied the effect of ultrasonic cleaning of vinyl records back in the late 70s when I built my first ultrasonic record cleaner. In my laboratory, we routinely used ultrasonic cleaners for many laboratory applications. Before I actually cleaned any records in an ultrasonic bath, I wanted to be sure that there were no detrimental effects. To evaluate the effectiveness of ultrasonic cleaning of records and to determine if there were any detrimental effects, I used several analytical techniques. My primary analytical techniques were Photoelectron Spectroscopy (HP 5950A Photoelectron Spectrometer) and optical microscopy (Olympus Laboratory Microscope at about 10,000X). Photoelectron Spectroscopy is sensitive to the top 5 nanometers of a sample surface and can determine the chemical structure of the record surface and the chemical composition of contaminants on the record surface. I also employed several supporting techniques for certain experiments including; Mass Spectrometry (MS), Liquid Chromatography (LC), Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). These experiments were all done on sacrificial records that were cut into 1 cm squares. These 1 cm square samples were analyzed before and after various cleaning procedures. In some cases, the test samples were purposely contaminated with finger prints and various greases and oils to simulate a heavily soiled record.
The variables Investigated include:
Ultrasonic Bath Solution:
1 - Triply distilled water prepared in my laboratory
2- Deionized water prepared in my laboratory
3 - The addition of either 2.5% or 5% concentration of an alcohol (either isopropyl or ethanol) to each of the above.
Surfactant - I experimented with several different nonionic surfactants which were in use in my laboratory. I settled on several alcohol ethoxylate surfactants with the general structure R(OCH2CH2)nOH where R is the alkyl chain and (OCH2CH2)n is the ethylene oxide (EO) chain. Their chemical structure varied with the length of the alkyl chain and/or the ethylene oxide chain. For reference, the alcohol ethoxylates I used are similar in structure to Dow’s Tergitol 15-S series of surfactants which are secondary alcohol ethoxylates.
Time in the ultrasonic bath - My experiments demonstrated that longer than a few minutes in the ultrasonic bath had little beneficial effect on the overall cleaning process and the possibility of a detrimental effect. Most of the cleaning took place in the first few minutes in the bath. I did observe that extended time in the bath would leach plasticizers, stabilizers or other additives from the bulk of the record test samples and eventually pit the record test sample surface. So I tried to keep the time in the bath to a minimum.
Summary of experimental results:
1. Both trtiply distilled water and deionized water in the ultrasonic bath worked surprisingly well at removing much of the contaminants on the test samples in many cases. Testing on UHV prepared Si wafers in the ultrasonic bath indicated that deionized water did leave some residue while triply distilled water left little to none that could be detected. The small amount of residue left by the deionized water is probably not a major concern.
2. The addition of the surfactant to the ultrasonic bath solution improved the overall contaminant removal efficiency compared to only water.
3. The addition of an alcohol to the ultrasonic bath solution had little effect on the contaminant removal efficiency except in a few select cases. For these few cases, ethanol was slightly better than isopropyl at contaminant removal.
4. All the surfactants that I tried exhibited similar contaminant removal properties and did a reasonably good job of cleaning heavily soiled record test samples. The biggest difference between the surfactants was the amount of residue left behind after the ultrasonic bath. In general, the lower molecular weight surfactants were found to leave less residue on the record test sample surface and were removed more easily with a distilled water rinse after the ultrasonic bath.
5. I will mention that I did try Dawn detergent just to see how effective it was at cleaning records and whether it had any detrimental effects. Dawn was very good at cleaning the most heavily soiled record test samples but left considerable residue which required an extended rinsing to remove. I would only recommend Dawn detergent for heavily soiled records and not for regular use. Dawn does contain as many as 17 ingredients, some of which may cause issues with records after long term exposure.
6. When I finally set up my ultrasonic cleaner for my records, I only used distilled water and the appropriate amount of the alcohol ethoxylate surfactant in the bath. I typically had it set at about 2 RPM and a run time of about 6 to 9 mins. That corresponds to actual exposure times of ~ 2 to 3 minutes (~1/3 of the record surface is in the bath at a given time). For my setup, between 1 to 3 RPM worked fine. The 6 min time was for my records purchased new which had no obvious contamination and the 9 min time was for previously owned records that exhibited some surface contamination. For records with significant visible contamination, I would add some ethanol (2.5 to 5%) to the bath solution.
The spindle assembly on my DIY ultrasonic cleaner could hold up to 10 records and had a variable speed motor attached. The assembly rode on a track with a lock nut so the spindle assembly could be raised and lowered into the bath. I actually employed 2 ultrasonic baths both fitted with a track to attach the spindle assembly. The second bath was only used with distilled water. Primarily I used this second bath to spin rinse records that had been cleaned in the first ultrasonic bath. In some cases I did a followup ultrasonic cleaning with distilled water in the second bath for heavily soiled records. After a distilled water rinse in the second bath, I would raise the spindle assembly and spin dry the records at a faster rate. This left no visible water marks on the record surface and only some residual water droplets on the record outer edges which I removed with a clean room wipe.
I used this ultrasonic cleaner for over 30 years with excellent results and never any issues with my records. Even new records exhibited an improvement in SQ after ultrasonic cleaning. Typically once a record is ultrasonic cleaned, it will need no further ultrasonic cleaning if handled properly. The total time to mount, ultrasonic clean, rinse and spin dry 10 records was typically about 20 minutes. Heavily soiled records might take a few minutes longer.
