The Groove Probe, for optimizing and evaluating record cleaning systems

I am writing to tell you about some fairly simple techniques that I have used to evaluate the effectiveness of record cleaning. I would like to be able to fine-tune my own system or to buy another system on the basis of something better than just listening and guessing how much dirt is left.
I thought it needed a name, so I call it the Groove Probe.  With the Groove Probe I was able to count the clicks and examine them and distinguish between dirt and scratches.

With any system there are almost always some clicks left, which could be either dirt, or scratches or other defects. It's difficult to tell the difference. A subjective listening test is helpful but somewhat limited. It would be much better if we could count the remaining defects, and distinguish between dirt and permanent defects.

Furthermore, every record cleaning system, whether expensive or inexpensive, has dedicated users who attest to wonderful results. But that's not very helpful for comparison, because you can find good or bad reviews for just about any system. The problem with almost all of these reviews is that I doubt whether they can distinguish between remaining dirt and defects.

The Method
Any turntable can be used as a scanning probe microscope that feels the groove and faithfully records every little defect. You just need to digitize the record as you play it. I call this the Groove Probe.

The sound file can be examined visually, which can be quite revealing. Also, there is software available that can be used to count pops and clicks.

I digitized a record after wet-cleaning and brushing with an Audioquest carbon brush. (The cleaning removed the release agent, so the needle doesn't accumulate gunk.  I also have no problem with static.) Then I played the record twice more, without moving it and without additional brushing. On the third play I digitized it again. (You could also digitize before and after cleaning, to directly determine the effectiveness of cleaning. However, I was more concerned with identifying the sources of the remaining clicks.)

To cound the clicks, I used ClickRepair in default stereo mode. (ClickRepair is available at modest cost, and it has a free trial version. Disclosure: I have no financial interest, and don't know the developer.)

Here is a count of the pops and clicks detected in a short excerpt.

1st play:
  12544 left
  18288 right
  4482940 total samples
 
3rd play
  8758 left
  13452 right
  4482940 total samples

The needle has removed 26 to 30% of the dirt after two plays!  This seems consistent with the visual evidence.  The needle acts like a snowplow, but of course the dirt could also settle again into the grooves.

To compare the files visually, I examined the "silent" gap between bands with Audacity (a free, open-source sound editor). I added a second stereo track and copied the third playing, so I could compare the tracks (before and after). I aligned the two tracks visually by dragging.

Apparently this forum doesn't allow images, so I can't show you the results. When you do this, it is quite easy to compare the tracks visually and see the changes.

Pops and clicks can easily be seen in all the tracks. However, some of them are gone, some are unchanged, and a few are new! Apparently there was quite a bit of dirt still in the grooves after cleaning. The needle has removed much of the dirt! The new clicks are probably due to dirt that has been moved, or possibly added. The remaining clicks, which have not moved or changed substantially, must be due to scratches or other defects in the record.