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Investigating if ultrasound is harming LPs

Description

Take a piece of a LP and US clean it.

With a precision weight scale. Taking the weight before and after the ultrasound cleaning. To determine IF any material is removed from the LP or not with the ultrasound usage.

 

Material 

The things that are needed for the test setup:

  • US DIY 6L cleaner. With 180 watt at 40 kHz.
  • Weight scale 2 decimals of a gram and max 5g capacity.
  • A piece of a real LP record 

 

Method

First I selected a LP and tried to cut out a piece that is as close to 5 grams. To get the maximum size as possible that the scale can support. Tried to get a piece that includes lead-in to lead-out. To especially get some of the "glossy" part of those.

 

I used the US cleaning to do an initial cleaning of the record ~5g piece.

 

When I was not interested in weight loss due to dirt coming off. I need to start with a clean piece that is just the LP material and nothing else. When the goal is to determine if the ultrasound is removing any material or not. 

 

For the US bath I used a little bit of heat 30°C and reverse osmosis RO water (more or less the same as distilled water). And some wetting agent.

When we want the scrubbing bubbles being able to work into the groove. The piece of the LP will hang in the water like a record is and not lay down in the bottom of the US bath tub. 

 

I will run the US machine timer set to 30 min. That in practice a LP is less than half of its area at any time in the bath. That means more than half of the LP area is not in the bath when the record is revolving during a normal cleaning session. So in practice by having this piece submerged and US cleaned effectively for 30 min is like someone is spinning and cleaning in the US bath for more than one hour ! So it is more correct to see this 30 min as over an hour of US cleaning if it were a whole spinning LP. 

 

For the weight scale I make sure that the LP piece is clean and dry. And I try several times to rule out deviation between measurements, if any. Method where I learned to put the piece of LP on the exact same place on the scale plus I for each measurement looked that it went back to 0.00 g when I picked up the piece. I also reseted by pressing tare and looking again so I got 0.00 before putting the piece on the scale to get a new reading. 

 

Calculation example if we have a 5 g piece and 1% of its material were removed. Then that 1% should weight 0.05 grams and 0.5% should be 0.025 gram. That is what I see no issues to detect on the weight scale when the repetition accuracy is greater than 0.025!

 

So this method should be able to detect if less than 0.5% of the LP were removed by the scrubbing bubbles by the ultrasound and it's usage of it. 

But I was not expecting what happened below..

 

1st try Results

The start weight of the cleaned LP piece:

  1. 5.01 gram
  2. 5.01 gram
  3. 5.01 gram
  4. 5.01 gram
  5. 5.00 gram
  6. 5.00 gram
  7. 5.01 gram
  8. 5.01 gram

Average: 5.0075 grams.


 

After US bath "cleaning" first weight session:

  1. 5.02 gram
  2. 5.02 gram
  3. 5.02 gram
  4. 5.01 gram
  5. 5.01 gram
  6. 5.01 gram
  7. 5.01 gram
  8. 5.01 gram

Average: 5.01375 grams.

 

Hmm here is something fishy business going on between the weight sessions..

 

After the first US bath "cleaning" second weight session:

  1. 5.02 gram
  2. 5.02 gram
  3. 5.02 gram
  4. 5.02 gram
  5. 5.02 gram
  6. 5.02 gram
  7. 5.02 gram
  8. 5.02 gram

Average: 5.02 grams.

 

So there is something going on between weighting sessions..

I have taken those two weighting sessions and the average of the 2 x 8 measurements is 5.016875 grams.

 

Second try cleaning 

Now I am repeating the 30 min (one hour see above) Ultrasound treatment/"cleaning" for a second time.

 

And will weigh it also in two sessions and see what we get.

After 2nd US bath "cleaning" first weight session:

  1. 5.02 gram
  2. 5.02 gram
  3. 5.02 gram
  4. 5.02 gram
  5. 5.01 gram
  6. 5.01 gram
  7. 5.01 gram
  8. 5.01 gram

Average: 5.015 gram

 

After 2nd US bath "cleaning" second weight session:

  1. 5.01 gram
  2. 5.01 gram
  3. 5.01 gram
  4. 5.01 gram
  5. 5.01 gram
  6. 5.01 gram
  7. 5.00 gram
  8. 5.01 gram

Average: 5.00875 gram

 

So after a second US cleaning round and having the 16 measurements from the first US cleaning round.

Average from the two measurement sessions is after the 2nd US "cleaning": 5.011875 grams.

 

Conclusion

Is that there might be some deviation between measurement sessions of some reason that I can't explain:

  • Maybe it would average out if I took more than 8 measurements.
  • I should take more than only 8 measurements before the first UC cleaning session, which is why I later doubled them.
  • And I felt that I got better and better in my measurements routine. So the later measurements are more stable and have higher repetition accuracy than the first ones had.

I could leave the first iteration out from this post, but I wanted you all to see the whole process and not manipulate the findings.

 

Of the conclusions above I feel and believe mathematically with more samples that the second round is the one to look at and dismiss the first round.

 

Before I did the second US "cleaning" the average weight of the 16 measurements were:

  • 5.016875

After the second US "cleaning" the average weight of those 16 measurements were:

  • 5.011875

5.011875/5.016875 = 0.999003363647

 

Almost 0.1% (0.0996636352%) less weight after the second US cleaning.

 

That can be one of two things or little bit of both also:

  1. Measurement deviation before and after measurements. And more repetitions and measurements could be done. But I will stop here.
  2. That actually a VERY tiny part is removed of the LP by US

 

It is up to you guys to decide what you believe the data means. 

 

But remember it is a rather powerful US with 180W and in practice a very long US cleaning session as explained above.

 

Another note in the method of what I observed was that the little LP part were moving around in the bath when it were only hanging in a string. Usually a record is more firm and stable when the scrubbing bubbles are acting on its surface. If that makes any difference for the outcome but worthy of a note.

​​​​​(I got images on all the things and measurements 40 (!) But this forum is making it hard for me to attach them here)

​​​​​

optimize

Showing 3 responses by antinn

antinn
369 posts
 

@terry9 & @lewm,

This is such a can of worms.  There are so many variables involved such as the record itself, of which we do not know the actual composition, but you may segregate to virgin and recycled, clear, black and colored.  But this would not cover the older composition that may have anti-static ingredients that may be exhausted from extended UT exposure.

Then you need to establish control for the ultrasonic tank.  If it's an inexpensive tank, can you believe the 'published' frequency and power; and other aspects such as power/volume and sweep frequency. Then you have rotating speed and of course duration and temperature.

Then you have the process chemistry - what exactly has been added - actual chemical and concentration.  To make it easier - just start with lab grade high purity to reduce the variability.  And the 800-lb Gorilla is how to dry.  The 'dry' surface will be influenced by the background environment.   

But, after all is said and done, what damage do you expect?  Assuming you eliminate water/solution residue as a variable, it should come down to damage of the thin high frequency side wall ridges or general surface erosion.  Damage to the side-wall ridges should result in loss of high frequency data.  But the damage may not be acute, but more chronic.  So, the damage does not become evident until after multiple plays.  Surface erosion may have no damage to frequency output, but it could increase the surface roughness which would then raise the background noise level.  But measurable weight loss is unlikely.  You could try sampling post cleaning the water for particle count, but you need to be able to differentiate record plastic from tank metal, possible but quite scientific.  So, @lewn is right that one of the best ways is to compare digital files before and after since hearing is so subjective.  

However, the 800-lb elephant is that unless the 'control' record is very clean, UT may alter the output but beneficially.  So, you need to first establish initial cleanliness w/o using UT?.  Too many pressing plants are very dirty with atmospheric contaminants including condensing organics from the lubricants used by the pressing equipment - all those moving parts are generally lubricated.

However, can UT damage a record, yes.  I am working with someone right now who was cleaning 25-min with a very powerful unit, very slow rotation and allowing the temperature to reach about 55C.  Chemical reaction rates generally double for each 10C temp increase, and cavitation intensity for lower kHz can also increase.  One recent late 1960's record finished with a mottled dull finish surface.  He said it still sounded OK.  He is now installing a cooler and increasing the rotation speed.

Just some casual thoughts.  

antinn
369 posts
 

The damage to the record can alter its physical dimensions or its physical properties.  Damage to the physical dimensions - any dimension change to the groove which can include change to the side wall modulations, or the material surface roughness 'may' be audible depending on the reproduction playback equipment (starting with the stylus shape), the listening environment and finally the listener.

Damage to the physical properties is much more insidious.  This can alter the durability of the record.  This damage becomes cumulative and if the degradation is graceful the listener may not notice unless they periodically compare the record to a control.  

UT is a high energy process and while there is no evidence that the record is heating on any bulk scale, that does not exclude what may be happening at the surface boundary as its bombarded with high energy implosions.  Heat is the main enemy of records.  If they overheat (beginning about 50-55C) PVC releases hydrogen chloride gas which if not scavenged by the internal stabilizer (part of the composition) the surface embrittles.  Once pressed, the record only has very limited stabilizer left.  Once its exhausted, that's it, any further excessive heating and its record damage.

So, because of uncertainty, being 'reasonably' conservative by keeping temps <40C, not spinning too slow (<~0.3 rpm), not using aggressive chemistry, not exposing for extended periods (>~20min); and at <60 kHz no crazy high power, there should be reason to suspect that UT is damaging the record.   But get on the wrong side of being conservative and UT can damage that record.  But trying to determine absolute thresholds of when and what damage will occur would be a serious scientific endeavor.  Although Olympus has some serious digital microscopes (magnification >15,000X) - check out the LEXT™ OLS5100 3D laser microscope that precisely measures shape and surface roughness at the 
submicron level.  But you can only measure a very, very small area, but probably better than scanning electron microscopes.

Just some casual thoughts.

antinn
369 posts
 

@terry9 ,

No, I did mean to say <60kHz.  Here are the basic UT rules:

1.  Power needed to produce cavitation is inversely proportional to kHz.  So, lower kHz requires less power to produce cavitation.

2. Cavitation bubble size is inversely proportional to kHz.  So, lower kHz produces a larger diameter bubble.

3. Cavitation intensity is proportional to the bubble size and the power into the tank.

Ergo, a lower kHz UT with a lot of power can produce very high cavitation intensity.

Take care,

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