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Scientific investigations of Stradivarius violins--an updated review article


Bruce Tai
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14 minutes ago, GeorgeH said:

Of course, assuming that the presence of Al is real, Dr. Tai has no proof whatsoever that it was actually put there by del Gesù himself and not by the his wood vendor or even somebody later, but lack of proof never stops him from treating his far-fetched speculations as if they are facts.

The only real "fact" that Dr. Tai has possibly shared is that he found some Al in two (2) tiny "flakes" allegedly from del Gesù instruments.

 

Can GeorgeH stop playing the parasitic game of distorting my messages? Can GeorgeH prove that the Strad and Guarneri violins he has heard are actually made by those masters, and offer statistical proof in his own defense? How many sigmas does GeorgeH plan to use to prove that he has even heard a Strad in his life? Is six sigma statistics enough to convince the rest of us? 

Show some courtesy for researchers who have done actual experiments on this topic, and let other people have a meaningful discussion without internet trolling. My collaborators have done ~4500 ICP-MS elemental measurements on dozens of wood samples (12 Cremonese). What has GerogeH done? 

GeorgeH, go start your own thread and say whatever you want. It's a free country. Create your own audience. Give your lectures on statistics. 

For those who are interested in fact-based violin discussions, attached is the Nagyvary paper that first found aluminum in Andrea Guarneri spruce. He reported 700 ppm, very similar to the 1200 ppm in del Gesu spruce we measured. However, Nagyvary's control spruce was either salt-seasoned or contaminated by sweat. Natural spruce has very low Na, <100 ppm. The fact that we don't see high Al in other Cremonese spruces (n=5) and maples (n=5) means that they were not sold with high Al. The wood seller sold wood planks in bulk and would not bother treating a few planks for a specific customer. Maple and spruce were sold by different merchants, as hinted in Pollens' book. The only high aluminum Strad sample we have is a poplar cello. So that's how we deduce that the individual makers took the spruce/maple home and applied the Al themselves. Stradivari sometimes added lots of NaCl but del Gesu did not do that. We have analyzed enough old cheap violins to determine what is sweat contamination and what is salt seasoning. Andrea Guarneri spruce analyzed by Nagyvary shows no sign of salt seasoning, with NaCl levels more consistent with sweat contamination. It's all about quantitation. ICP-MS is the best quantitative method for elemental measurements in these tiny wood samples.

Even with limited samples, it was obvious that Stradivari and Guarneri were doing extensive chemical experiments. It does not mean that modern makers should repeat that. Why add minerals at all? Why not add minerals not available to Stradivari? I merely want to know what Cremonese were doing for my own curiosity, and imagine about their operations in my own way. 

 

nagyvary on cremona color 1982 VSA.pdf

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54 minutes ago, Bruce Tai said:

Even with limited samples, it was obvious that Stradivari and Guarneri were doing extensive chemical experiments.

This is not "obvious" at all. You don't know if the treatments were being done by some wood suppliers. There may have been a market for wood pre-treated with preservatives. Do you know how del Gesù bought his wood or who he bought it from?

You say that "The fact that we don't see high Al in other Cremonese spruces (n=5) and maples (n=5) means that they were not sold with high Al," but N=5 (where from? random? non-random?) samples is not enough to say this with any certainty. (BTW, do you see any Al in these samples?) You don't know who his wood supplier was and/or if the supplier was treating the boards with alum or something else. Perhaps they were treating all their wood with preservatives.

Perhaps the wood suppliers were the ones doing "doing extensive chemical experiments."

You draw a lot of big conclusions on very little evidence. The fact that you found Al on a few flakes of wood does not mean that del Gesù soaked his wood in alum. In fact, there are many possible explanations of how it got there. 

Skepticism is in science is a virtue, not a fault. Confirmation bias in science is a fault, not a virtue. As long as you keep asserting far-fetched speculative statements as facts when they are not supported by any data, I will point this out out. 

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Ignoring the troll.... It's plain silly to comment on the scope of the study before reading the whole paper, which has not been published yet. Patience is a virtue. 

Nagyvary had one Andrea Guarneri spruce and made some quick measurements. He thought the Al was added intentionally.  

Forty years later, our data are consistent with Nagyvary's original interpretation. That's called reproducibility. Patience is a virtue. The Guarneri family had a special preference for aluminum. Three out f three, completely independent samples. Grandfather and grandson. Neighbors did not add it. It's very telling. 

All my alchemical studies suggest that alum was the most probable source of aluminum. Is there any other possible candidate?

There were three kinds of alums available. KAl(SO4)2, NH4Al(SO4)2, Al2(SO4)3. We cannot tell them apart in our data. The ammonia one was purely synthetic. The other two could be synthetic or purified from natural sources. It was easy to recrystallize alum. So the alchemists were pretty obsessed with their beautifully pure and clear crystals. 

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I already presented the hypothesis that wood suppliers may have done the chemical treatments in my 2017 PNAS paper. GeorgeH is now using our older hypothesis to do the trolling, brilliant. 

Quoted from my PNAS paper:

"Because violin plates are only a few millimeters thick, dimensional stability is an extremely important tonewood quality. Immersion of dried tonewood into liquids is likely to cause swelling damage and compromise dimensional stability, and is therefore generally avoided. Before the introduction of pressurization methods in the 1800s, extensive mineral penetration by soaking or sap displacement was probably only achievable with water-saturated wood, before full drying took place—likely applied by wood suppliers rather than violin makers."

Our extensive new data goes against the wood supplier hypothesis. Also, sap displacement was probably too much work. Andreas Preuss showed me that he can take dried tonewood, soak it, and properly dry it again in the workshop. I did not know that in 2016. 

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I don't think discussions can be productive if incessant trolling is not controlled by the moderator. The original poster should have the right to ask the incessant troll to be locked out from making further posts in this thread. The internet troll, GeorgeH, is repeating the same message over and over again without any insight to add. 

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2 hours ago, Bruce Tai said:

For those who are interested in fact-based violin discussions, attached is the Nagyvary paper that first found aluminum in Andrea Guarneri spruce. He reported 700 ppm, very similar to the 1200 ppm in del Gesu spruce we measured. However, Nagyvary's control spruce was either salt-seasoned or contaminated by sweat. Natural spruce has very low Na, <100 ppm. The fact that we don't see high Al in other Cremonese spruces (n=5) and maples (n=5) means that they were not sold with high Al. The wood seller sold wood planks in bulk and would not bother treating a few planks for a specific customer. Maple and spruce were sold by different merchants, as hinted in Pollens' book. The only high aluminum Strad sample we have is a poplar cello. So that's how we deduce that the individual makers took the spruce/maple home and applied the Al themselves. Stradivari sometimes added lots of NaCl but del Gesu did not do that. We have analyzed enough old cheap violins to determine what is sweat contamination and what is salt seasoning. Andrea Guarneri spruce analyzed by Nagyvary shows no sign of salt seasoning, with NaCl levels more consistent with sweat contamination. It's all about quantitation. ICP-MS is the best quantitative method for elemental measurements in these tiny wood samples.

Dear Bruce, Aluminium is one of the most present materials on land. In college we learnt about the SiAl layer and the SiMa layers, the former on land or former land, and the last on seabeds or former sebeads. AluminiumOxide is present in clay and earth and will be present in dust everywhere, abrasives quite possibly.
It is nothing special with finding aluminium on objects on land. 

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5 hours ago, Bruce Tai said:

It was incorrectly assumed that saturated alum was good for preserving the wood of unearthed Viking ships. The wood ended up absorbing 40%(? need to check the scientific reports) of its weight in alum. As Buen pointed out, sulfuric acid was generated and basically hydrolyzed what's left of the wood. A big blunder. 

Alum was used by ancient Romans for wood preservation and flame retardation, recorded in writing (need to go to my notes for the author's name). The key is of course the dosage. Eat too much salt, people die; Eat to little salt, people die. But salt is essential. 

I speculate that del Gesu might have thought the right amount of alum was essential, in combination with the other funky things he did. I don't know why he even added some Zr4+ into his wood. At 40 ppm it's not going to do much, probably a contaminant from something else that was fishy and clandestine. 

What can 1000 ppm or 3000 ppm of aluminum possibly do? Good question, Buen. We tested those amounts on cellulosic diaphragms for headphones. They caused enhanced bass response below 500 Hz by 1-2 dB. Nothing huge, but easily measurable. We have not had the chance to test on wood bars. But it shows that mechanical properties can be subtly affected at 3000 ppm of Al3+ crosslinking. We put in 9000 ppm of Na+ and nothing happens.  

So small enough amounts of alum is good and too much is detrimental? Where does the limit go? I am naive enough to think it is dangrous to the wood even at small amounts.

1-2 dB is hardly a signal and it is probaly not audible. The measurement precision is probaly larger than these numbers. 

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I think if the alum is precipitated too quickly and at high concentration you are going to trap sulfate ion in the wood causing it to decompose. I think slowly raising the ph and liberal washing would work. If one was to work out a process it would involve taking cross sections of the wood, checking for penetration(AL) and sulfate content.

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Alum seem to have been used as a mordant in the old textile industry, and possibly leather tanning. It is interesting to read about it and the crystals looks mesmerizing. It has been used for sizing of paper too. 

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2 hours ago, Bruce Tai said:

It's plain silly to comment on the scope of the study before reading the whole paper, which has not been published yet. Patience is a virtue. 

I think it is "plain silly" for you to discuss your unpublished study and then expect others to not discuss it, or suggest that MN moderators not allow posts critical of your conclusions. 

My last post asked about this:

4 hours ago, Bruce Tai said:

The fact that we don't see high Al in other Cremonese spruces (n=5) and maples (n=5) means that they were not sold with high Al.

There were thousands and thousands of wood sales over many decades by many vendors during the golden age of Cremonese violin-making. Analyzing 5 samples of spruce and 5 samples of maple as controls is hardly sufficient to justify your conclusions that del Gesù himself soaked his wood in aqueous alum, and that "Stradivari and Guarneri were doing extensive chemical experiments." 

And I am also interested in where and how these samples were obtained and if any Al was detected in them. 

It isn't trolling to disagree with you or to ask questions.

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3 hours ago, Bruce Tai said:

All my alchemical studies suggest that alum was the most probable source of aluminum. Is there any other possible candidate?

As noted by @Anders Buenaluminum is very common in some minerals.  I'd suspect various clays, which can contain large percentages of aluminum.  Several have been used for aluminum ores using both acid and alkaline processes which yield soluble salts.  If someone was using a clay as part of a ground recipe, you'd find it for sure.  Some aluminum compound could have leached from an unglazed ceramic container used for soaking something, too.

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45 minutes ago, Violadamore said:

As noted by @Anders Buenaluminum is very common in some minerals.  I'd suspect various clays, which can contain large percentages of aluminum.  Several have been used for aluminum ores using both acid and alkaline processes which yield soluble salts.  If someone was using a clay as part of a ground recipe, you'd find it for sure.  Some aluminum compound could have leached from an unglazed ceramic container used for soaking something, too.

Different trees tolerate different aluminium content in the soil. Maple and Spruce grow well in acid soil.

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7 hours ago, Anders Buen said:

Dear Bruce, Aluminium is one of the most present materials on land. In college we learnt about the SiAl layer and the SiMa layers, the former on land or former land, and the last on seabeds or former sebeads. AluminiumOxide is present in clay and earth and will be present in dust everywhere, abrasives quite possibly.
It is nothing special with finding aluminium on objects on land. 

The X-ray fluorescence imaging at SwissLight synchrotron shows that Al was diffusely distributed into wood cells. That had to be soluble Al. Aluminum silicates and aluminum oxides are common but insoluble. I don't know any other soluble aluminum salt sold at premodern apothecaries except for alums. 

 

 

 

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7 hours ago, Anders Buen said:

So small enough amounts of alum is good and too much is detrimental? Where does the limit go? I am naive enough to think it is dangrous to the wood even at small amounts.

1-2 dB is hardly a signal and it is probaly not audible. The measurement precision is probaly larger than these numbers. 

Wood itself is about pH 4 or 4.5. Small amounts of alum is safe. Wood has its own pH buffering capacity. No one knows the real limit in the long-term stability. A

We tested with iPhone earbud diaphragms. Thanks to precision manufacturing, their frequency response curves are extremely reproducible, measured on special testing equipment. Mastering engineers  won't consider 2 dB bass boost inaudible. As you noted, it's too hard to measure small changes on wood, too much variability. Headphone diaphragms much more consistent. Our point was to show that 3000 ppm Al provides sufficient chemical bonds to stiffen the material. Young's modulus also increased a bit but statistically significantly. We don't expect a very drastic effect anyway. The blind tests by Fritz et al. suggests that differences between Cremonese and modern master violins are subtle at best.    

No ones knows how much Al is enough to cause what effect. The dosage is the key. The Cremonese had a long period to experiment with it. Decades or even a century. A lot of their customers were local families. Cremonese makers had the chance to reinspect their products even after 100 years. We don't have that luxury. 

 

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12 hours ago, Bruce Tai said:

Which wood did you steam? 

We have learned that boiling spruce can promote cellulose rearrangement but boiling maple cannot. 

There are fundamental differences between softwood and hardwood. A topic that is underexplored. We are just beginning to explore. 

 

12 hours ago, Don Noon said:

The time or two I boiled spruce, the rectangular cell structure collapsed.  I never tried boiling maple, but the smaller, more round cell strucure I think could be more stable.

Just for clarification. Boiling and steaming are two different procedures.

For boiling the wood needs to be immersed in boiling water.  I tried it too on small wood samples but abandoned the idea after the first test. 
 

I am doing steaming which is exposing wet wood to hot steam in a specially made steam chamber. Once I was able to monitor the inside temperatures which was between something like 90 and 95 Celsius. When water would run out from the water tank the temperature would drop below 90 Celsius.

My first test was with green wood without soaking on a special order to a wood dealer.

Later I tried variants of soaking the wood, with different results. 

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14 hours ago, GeorgeH said:

Of course, assuming that the presence of Al is real, Dr. Tai has no proof whatsoever that it was actually put there by del Gesù himself and not by the his wood vendor or even somebody later, but lack of proof never stops him from treating his far-fetched speculations as if they are facts.

The only real "fact" that Dr. Tai has possibly shared is that he found some Al in two (2) tiny "flakes" allegedly from del Gesù instruments.

 

I am not a scientist to verify or disprove your arguments. I only know that Dr. Tai is doing his research the best he can in the minefield of variables. I am sure that he prepared his samples to avoid any contamination’s from coatings etc. and compared them with wood of a similar age group. He asked me as well to send him samples of wood with my treatment to have a comparison to wood where the treatment procedure is known.

The fact that he has to work with only very few samples is an obstacle all scientists face in this situation. (Try to convince the owner of a now multimillion dollar object to chunk off one cube millimeter of his/her precious possession....)  If we look on all the investigations in this field, I cannot remember any which based the result on many samples. Usually scientists open a very mall window to find clues. Sometimes a fraction of varnish or wood small as one square millimeter serves as basis for a research project. So did Woodhouse Et al., Nagyvary, Brandmaier Et al., Echard et al. Dr. Tai’s research is no exception.

Reviewing the history on the search for the ‘Cremonese secret’ we can safely say that scientists looked into basically all thinkable variables so far, except wood treatment. Alone the fact that the wood of those instruments shows abnormal proportions of certain elements should be good enough to look a bit deeper into it. Though I am not subscribing to the idea that GDG desperately soaked his wood in an attempt to compete with Strad, there must have been somewhere some reason for which Aluminium got into the wood structure and apparently more than is found in naturally aged wood. I find however more interesting that Chlorine in rather high amounts could be identified in Strads wood. Natrium chloride is the only possible source (otherwise there is only one rare volcanic ash mineral containing Chlorine which seemed to have been accessible to makers in Italy in the 18th century) and is neither used as an ingredient in the ground nor in the varnish. If all the wood from Bosnia was transported by floating it in the Adriatic, Guarneris wood should show the same analytical amounts. This gives some strong indications that something has been done. Who and when poses big question marks and Dr. Tai is saying in this respect that there is still a long way to go.
 

My own take as a maker on such findings is always to figure out if those scientific hints make sense when making instruments. I find it interesting enough that Strad samples and Guarneri workshop samples seem to be distinguishable different. 
 
In a scientific sense it would maybe good if a different research group would try to analyze the wood  with a different approach. I am sure Dr. Tai wouldn’t oppose.

 

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3 hours ago, Bruce Tai said:

Wood itself is about pH 4 or 4.5. Small amounts of alum is safe. Wood has its own pH buffering capacity. No one knows the real limit in the long-term stability. A

We tested with iPhone earbud diaphragms. Thanks to precision manufacturing, their frequency response curves are extremely reproducible, measured on special testing equipment. Mastering engineers  won't consider 2 dB bass boost inaudible. As you noted, it's too hard to measure small changes on wood, too much variability. Headphone diaphragms much more consistent. Our point was to show that 3000 ppm Al provides sufficient chemical bonds to stiffen the material. Young's modulus also increased a bit but statistically significantly. We don't expect a very drastic effect anyway. The blind tests by Fritz et al. suggests that differences between Cremonese and modern master violins are subtle at best.    

No ones knows how much Al is enough to cause what effect. The dosage is the key. The Cremonese had a long period to experiment with it. Decades or even a century. A lot of their customers were local families. Cremonese makers had the chance to reinspect their products even after 100 years. We don't have that luxury. 

 

Using the lightest possible material for a test of a substance is the best method of getting results. The changes are likely to be dependant on the surface mass of the test object and the added mass sortof like 20log(m+dm) if the m is small you easily get effects. If the mass, m, is larger, like 2,5mm spruce, the effect is likely to be very small.

After reading about the wide use of alum, even today (eg in deodorants and cosmetics), I think it is plausible or not impossible that it can be found on old or even new wood or in the varnish. 

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1 hour ago, Anders Buen said:

After reading about the wide use of alum, even today (eg in deodorants and cosmetics), I think it is plausible or not impossible that it can be found on old or even new wood or in the varnish. 

Perhaps Guarneri used alum as a deodorant/anti- perspirant, and it ended up all over the place.

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19 hours ago, Bruce Tai said:

Can GeorgeH stop playing the parasitic game of distorting my messages? Can GeorgeH prove that the Strad and Guarneri violins he has heard are actually made by those masters, and offer statistical proof in his own defense? How many sigmas does GeorgeH plan to use to prove that he has even heard a Strad in his life? Is six sigma statistics enough to convince the rest of us? 

Show some courtesy for researchers who have done actual experiments on this topic, and let other people have a meaningful discussion without internet trolling. My collaborators have done ~4500 ICP-MS elemental measurements on dozens of wood samples (12 Cremonese). What has GerogeH done? 

GeorgeH, go start your own thread and say whatever you want. It's a free country. Create your own audience. Give your lectures on statistics. 

For those who are interested in fact-based violin discussions, attached is the Nagyvary paper that first found aluminum in Andrea Guarneri spruce. He reported 700 ppm, very similar to the 1200 ppm in del Gesu spruce we measured. However, Nagyvary's control spruce was either salt-seasoned or contaminated by sweat. Natural spruce has very low Na, <100 ppm. The fact that we don't see high Al in other Cremonese spruces (n=5) and maples (n=5) means that they were not sold with high Al. The wood seller sold wood planks in bulk and would not bother treating a few planks for a specific customer. Maple and spruce were sold by different merchants, as hinted in Pollens' book. The only high aluminum Strad sample we have is a poplar cello. So that's how we deduce that the individual makers took the spruce/maple home and applied the Al themselves. Stradivari sometimes added lots of NaCl but del Gesu did not do that. We have analyzed enough old cheap violins to determine what is sweat contamination and what is salt seasoning. Andrea Guarneri spruce analyzed by Nagyvary shows no sign of salt seasoning, with NaCl levels more consistent with sweat contamination. It's all about quantitation. ICP-MS is the best quantitative method for elemental measurements in these tiny wood samples.

Even with limited samples, it was obvious that Stradivari and Guarneri were doing extensive chemical experiments. It does not mean that modern makers should repeat that. Why add minerals at all? Why not add minerals not available to Stradivari? I merely want to know what Cremonese were doing for my own curiosity, and imagine about their operations in my own way. 

 

nagyvary on cremona color 1982 VSA.pdf 1.32 MB · 9 downloads

This is rather old work.  Nagyvary and others have done a lot more since 1982.

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6 hours ago, David Burgess said:

Perhaps Guarneri used alum as a deodorant/anti- perspirant, and it ended up all over the place.

Or his wife or female players cryed so hard when playing that the mascara with alum floated all over the instrument. 

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9 hours ago, Andreas Preuss said:

I am not a scientist to verify or disprove your arguments. I only know that Dr. Tai is doing his research the best he can in the minefield of variables. I am sure that he prepared his samples to avoid any contamination’s from coatings etc. and compared them with wood of a similar age group. He asked me as well to send him samples of wood with my treatment to have a comparison to wood where the treatment procedure is known.

The fact that he has to work with only very few samples is an obstacle all scientists face in this situation. (Try to convince the owner of a now multimillion dollar object to chunk off one cube millimeter of his/her precious possession....)  If we look on all the investigations in this field, I cannot remember any which based the result on many samples. Usually scientists open a very mall window to find clues. Sometimes a fraction of varnish or wood small as one square millimeter serves as basis for a research project. So did Woodhouse Et al., Nagyvary, Brandmaier Et al., Echard et al. Dr. Tai’s research is no exception.

Reviewing the history on the search for the ‘Cremonese secret’ we can safely say that scientists looked into basically all thinkable variables so far, except wood treatment. Alone the fact that the wood of those instruments shows abnormal proportions of certain elements should be good enough to look a bit deeper into it. Though I am not subscribing to the idea that GDG desperately soaked his wood in an attempt to compete with Strad, there must have been somewhere some reason for which Aluminium got into the wood structure and apparently more than is found in naturally aged wood. I find however more interesting that Chlorine in rather high amounts could be identified in Strads wood. Natrium chloride is the only possible source (otherwise there is only one rare volcanic ash mineral containing Chlorine which seemed to have been accessible to makers in Italy in the 18th century) and is neither used as an ingredient in the ground nor in the varnish. If all the wood from Bosnia was transported by floating it in the Adriatic, Guarneris wood should show the same analytical amounts. This gives some strong indications that something has been done. Who and when poses big question marks and Dr. Tai is saying in this respect that there is still a long way to go.
 

My own take as a maker on such findings is always to figure out if those scientific hints make sense when making instruments. I find it interesting enough that Strad samples and Guarneri workshop samples seem to be distinguishable different. 
 
In a scientific sense it would maybe good if a different research group would try to analyze the wood  with a different approach. I am sure Dr. Tai wouldn’t oppose.

So this is the point - one cannot assume or “be sure” of anything because we don’t know and Dr. Tai hasn’t said. This is why discussion of methods and materials is critical information in any presentation of scientific data. What we don’t know includes:

  • When were the samples were obtained?
  • How were they were obtained?
  • What specific violins did they come from?
  • What specific locations on the violins did they come from?
  • Where did the control samples come from?
  • How were the samples stored?
  • How long were the samples stored?
  • What containers were the samples stored in?
  • How were the samples prepared for testing?
  • How were the tests performed?
  • How many tests were performed on each sample?
  • What is the experimental error of the tests on these specific kinds of sample, e.g. accuracy and precision?

And so forth.

Without any of this information, it is impossible to judge the veracity and usefulness of the data or to draw any conclusions from it.

Furthermore, even if the data turns out to be real and scientifically defensible, it is simply impossible to say if Stradivari or Guarneri had anything to do with it. There are other potential and equally likely reasons to explain the results that have nothing to do with either one, but confirmation bias is a powerful thing.

And if you want to find out the confirmation bias of the investigator, just find out who is paying for the research.

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