Thumbs up for ultrasonic record cleaning

@jtimothya 

Don't see why a mixture of frequencies should be better. There was a graph posted in the DIYAudio thread of cleaning efficacy vs frequency. For gaps the size we see on records, 40KHz is only marginally superior for the largest gaps, and quite inferior for the smallest. This mirrors my experience.

IMO, 40C is low - only a touch above body temperature. I often start a session with a temperature in the low 40's, but continue to begin 15 minute runs until the temperature hits 47C, when I wait for the chemistry to cool a bit. I acknowledge that it can be disconcerting to see your vinyl come out of the tank a little warped, but with uniform cooling in the rinse stage, the warp disappears. At least in my experience, by my standards. I use a 60RPM Vinyl Stack and running purified water for rinse.

Are you sure that your thermometer is accurate? And that it is monitoring the relevant temperature? Stir the chemistry vigorously - if the temp reading changes, then your tank is not homogenizing the chemistry and hot spots or cold spots may emerge with use. That could be affecting your perceptions of appropriate temperature. Hope that helps.

Correction: substitute "particles" for "gaps". Should read "For particles the size ..."

@jtimothya 

Don't see why a mixture of frequencies should be better. There was a graph posted in the DIYAudio thread of cleaning efficacy vs frequency. For gaps the size we see on records, 40KHz is only marginally superior for the largest gaps, and quite inferior for the smallest. This mirrors my experience.

IMO, 40C is low - only a touch above body temperature. I often start a session with a temperature in the low 40's, but continue to begin 15 minute runs until the temperature hits 47C, when I wait for the chemistry to cool a bit. I acknowledge that it can be disconcerting to see your vinyl come out of the tank a little warped, but with uniform cooling in the rinse stage, the warp disappears. At least in my experience, by my standards. I use a 60RPM Vinyl Stack and running purified water for rinse.

Are you sure that your thermometer is accurate? And that it is monitoring the relevant temperature? Stir the chemistry vigorously - if the temp reading changes, then your tank is not homogenizing the chemistry and hot spots or cold spots may emerge with use. That could be affecting your perceptions of appropriate temperature. Hope that helps.

It's not just about size.  What particle sizes do "we see on records." ?  I don't think there is a univeral range.

If audiogon allowed posting pictures I'd do that here. Take a look at the graph on p.16 of this PDF: 
http://www.idema.org/wp-content/downloads/1622.pdf This is about cleaning perpendicular magnetic tape but it should give you a basic idea. 

Also take a look at my article here:https://thevinylpress.com/timas-diy-rcm-follow-up-2-compelling-changes-improved-results/

There is quite a bit of information on the Web about use of multiple frequencies in USC. Don't just stick to threads about record cleaning, there is a ton of junk information to sift through in audio forums. We are still learning, mostly from trial and error, but the technology has been in the industrial areas for quite a while. Here's one example about particle size and frequency; you can find more with a little research of your own:
https://techblog.ctgclean.com/2019/09/micron-size-vs-frequency/

Wrt temperature, there is a relationship between solution composition, heat, and cleaning efficiency.  Wrt VersaClean, what is the TDS ppm using that in solution?  I prefer high purity IPA.  PhotoFlow is not recommended - a little research will tell you why.

Of course, people can do whatever they want based on what they believe. I'm only passing along based on my experience and research.

Thank you for the references, which mainly point out that there is very little formal research on US cleaning, beyond the obvious and the theoretical. Let me give you another reference: the Rushton thread (2016) here on Audiogon, to which I contributed extensively.

It seems that we mostly agree, but:
1) temperature. Your references suggest that low frequency US cleaning might be more effective at removing fats and oils. As I mentioned in the Rushton thread, I had thought so too until I found that it was a temperature effect. The lower frequency US did a better job of cleaning oils, while heating the chemistry more. When I controlled for temperature, the low frequency advantage disappeared. So I use 80KHz, sweep function, and 45C.
2) frequency mix - see above.

By the way, I have done a fair bit of trial and error, including 2000 odd records which were inadequately rinsed! So I had to do the whole lot again, with a better regime: rinsing under running highly purified water followed by a distilled water bath. Air dry in a clean-ish room.

By TDS I assume you mean total dissolved solids. I use distilled water for cleaning, so total dissolved solids is very low - for the first 2 records. Naturally that increases with each pair. That increase is roughly indicated by the colour of the chemistry, which is close enough for hobby work. For suspended solids, I allow the chemistry to settle and use the valve on the ElmaSonic to drip solid-free chemistry into a jug. I use VersaClean 2.5%.

By IPA, I assume that you mean isopropyl alcohol. I don't use anything volatile and flammable, because, while it is easy to monitor and regulate vapour in a lab, it is hard in a garage. Since my Elma machine can be an ignition source, I avoid the hazard.

I also see that you are cleaning 6 records at a time, which means a spacing of at most 33mm. That spacing is OK for 80KHz, about 1.7 wavelengths, but, at less than a wavelength, that spacing is quite inadequate for 37KHz. Also, with 6 records your effective US power per record is down to about 55W. I find that I get better results at 75W. YMMV