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Bruce Tai

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Everything posted by Bruce Tai

  1. That's good to know. Is this a recent CT measurement?
  2. The reason I say alum and potash is because they are fuzzy terms but historically accurate terms. Renaissance alchemists named chemicals that way for practical reasons and limitations. Potash (pot ash) can be made from burning wood or grass. Depending on the temperature, it can be K2CO3 and KOH in different ratios. A lot of CaO may be present, but they can be removed by some means. A purer kind of potash can be made from burning potassium tartrate (tartar, wine stone) or burning potassium bitartrate (cream of tartar). The product is called burnt tartar or Alumen faecis, high-purity K2CO3. Alum has many names in medieval texts but dyer's alum is almost always KAl(SO4)2. Ancients knew how to make highly pure synthetic KAl(SO4)2 by recrystallization. They also prepared NH3Al(SO4)2 similarly, also called alum. Natural alum may be KAl(SO4)2 or Al2(SO4)3. Al2(SO4)3 was chemically produced in large quantities in the 19th century for industrial use. I think an entire book may be written about alum's history. I am just giving a very brief summary.
  3. https://www.bormanviolins.com/pdfs/VSAPBormanandStoel.pdf This paper has different measurements for the Titian Strad Density: spruce 0.368; maple 0.579 Weight: top 61.7g (no bass bar); back 93.6g
  4. I can imagine that CT density may be a few percent off. But 48.1 and 66.6 is night and day difference. I have never done violin CT. I wonder how reliable it is. So what is the lightest Strad top out there? Joseph curtin reported 54 and 55.5 grams without bass bar in a Strad magazine article if I remember correctly.
  5. Assuming 550 cm^2 (includes arching), 2.3 mm thick, 0.35 density, that's 44.3 g. Bass bar 4 g -> 48.3 g. Very close to the Titian measurements. Am I more correct this time?
  6. As you can see from our published photos that have been color-calibrated, the answer is no.
  7. So David, what is the area of the violin plate? Is it 500 square centimeter? I am trying to calculate average thickness based on the area. But the area number is difficult to find on the net. What is the average thickness of the Titian top?
  8. Sorry, website glitch. Multiple posts.
  9. Sorry, website glitch, multiple post.
  10. Sorry, website glitch. Multiple post.
  11. Thanks a lot. I have read this thesis before but missed the data. The top is 48.1 g with bass bar with wood density of 0.35. So the average thickness may be 0.24-0.25 mm. That's a very thin top made of low density spruce. And yet it survived well and sounds great. And yet Joseph Curtin thought a 54 g top without bass bar (for a Strad) is already very light.
  12. In a nutshell, the relevant ones are: Minor additives (tens of ppm): copper sulfate, iron sulfate Major additives (thousands of ppm): 1. Stradivari: table salt, potash 2. Del Gesu: alum, lime We don't know the order and application conditions. We don't know about washing or potential baking/boiling steps.
  13. Unfortunately we still don't have publicly available CT data that tell us about the weight, density, thickness, and weight at the same time. It would be important to know if the very thin Strad plates were built wit denser wood. More importantly, CT cannot reveal chemical composition. So we don't know if Stradivari also adjusted thickness according to wood treatment method.
  14. Hi Andreas, Do we know that Poggi used natural wood? Do you think he has any secret?
  15. Endless debates on who is the peak and who sounds better seems futile, I think we should be debating the thickness pf soundboards, because it is measurable. Let me quote from the Hill book on Stradivari: "It has at various times been asserted that Stradivari erred in the adjustment of his thicknesses, and made his instruments too thin. Fortunately, such statements invariably proceed from persons whose knowledge of Stradivari's work is very limited. The more thought we give to the subject, the more reason we see to hesitate in speaking positively for or against such a view. " I cannot find any other source willing to discuss this issue in a straightforward manner. Did Stradivari make his soundboard thinner than modern makers on average? I am sure some modern makers tried to copy Stradivari's extra-thin soundboard (2.0-2.4 mm in center). Good results or bad results?
  16. Since we have analyzed a bunch of aged tonewoods from antique Chinese zithers, we have now further insights into wood aging. By antique we mean softwood up to 250-2250 years old; hardwood from 250-700 years old. We also did artificial aging. Hemicellulose in hardwood decomposes more easily in natural aging. Softwood cellulose rearranges more easily in artificial aging. (This will be published in a couple of years) Antique Chinese zither makers were pretty crazy in both artificial aging and using very old wood (>500 years) . It may not be totally crazy to think that the soundboard can survive 1000+ years in violins. But I doubt that the maple back will last more than 600 years. When we recorded violins from 1560 and 1570 in my Savart Journal paper, they seem to be fine. So 450 years is still OK for maple.
  17. My dear friends, I have been talking about a study analyzing the spruce soundboards of Cremonese masters for several years. It is now published in Angewandte Chemie, one of the top three chemistry journals out there (files attached): https://onlinelibrary.wiley.com/doi/10.1002/anie.202105252 We paid $5000 for the open access option so that everyone can read it. We also made an Excel spread sheet containing all the ICP-MS data but it does not seem to be available yet. I will ask them why. There is a plan to write an accompanying article in the Strad to better explain the findings to luthiers. Your suggestions on what I should explain further would be appreciated. Also, we must not forget that Remy Gug correctly predicted 80% of our findings more than 30 years ago, in his two Strad articles: Salts of Wisdom (1987, issue 1166) Salted Soundboard and Sweet Sounds (1991 issue 1214). Anyone knows how Remy Gug got it so right? Many people have told me many theories about Stradivari's secrets. Gug made the best predictions so far. My Xerox copies of these two articles have shown wear and tear. I would appreciate if anyone could scan them as PDF and send the files to me. Thanks in advance. 1980445727_2021AngewStradSpruce.pdf 1132972592_2021AngewStradSpruceSI.pdf
  18. Some of those twelve layers are not original. So I would focus on the first 3 or 4 on top of the wood. Not sure how many layers are later additions. Nonetheless, we do see the combined effects of all twelve layers with our eyes. So it still helps explain the visual appearance. Titian sometimes put 30 glazing layers on his oil paintings to achieve amazing effects. God bless his poor assistants.
  19. I have re-read the three excellent articles by Fiocco and co-workers (attached below). Although they did not identify new ingredients, their X-ray tomography (micro-CT) study on stratigraphy is excellent. Fiocco's conclusions are quite different from the Brandmair and Echard(who favor no mineral particles), and somewhat closer to Nagyvary's older studies (who favor mineral particles). Brandmair and Echard mostly focused on Strad violins. Fiocco and Nagyvary studied mostly Cremonese and old Italian cellos (basses). Maybe that's why they come to different conclusions. In my recent AsiaChem article I presented a figure mostly based on Barndmair and Echard ideas . Now I made a new figure incorporating Fiocco's ideas for old Italian cellos . There are lots of contradictory observations and instrument limitations, but I try my best to use a cartoon to show the range of techniques employed by old masters. Notes on chemical compositions Strad violins system 1. wood 2. wood surface sealer/stain: protein, colorants (non-film-forming) [ground] 3. pale varnish: oil-resin 4. color varnish: oli-resin, colorants Old Italian cello system 1. wood 2. sealer layer: mineral particles, proteins [ground and filler particles] 3. color layer (proposed by Fiocco): colorants, mineral particles (?), the medium being oil-resin and/or proteins (?) 4. pale varnish: oil-resin 5. color varnish: oli-resin, colorants The new color layer proposed by Fiocco is quite confusing. Is it possible that protein can be mixed with oil resin with added colorants and mineral particles? They are not very sure either, the evidence is still weak. This may be the emulsion color varnish idea that has been proposed many years ago. In the old Italian cello system there is the liberty to change the order of layers 3-5 and even apply additional layers. My cartoon is just showing the range of techniques possible. I never studied any antique varnish samples so I am just offering objective summaries of published research. What I have not shown in the cartoon is the crushing of top wood cell layers. This is seen for some instruments, possibly using burnishing stone or scrapers. I believe that the basic themes of old Italian varnishing have been mostly uncovered. There could be many variations on top of these basic themes. Fiocco 2017 comparison of Amati Stradivari Guarneri varnish.pdf Fiocco 2018 guarneri cello varnish layers.pdf 347239661_Fiocco2019Brescianvarnishprotein.pdf 2026683730_2020AsiaChemCoverStory.pdf
  20. Thanks for the information. So it's the Vollers who were the cunning copyists, not Vuillaume. Dendrochronology is amazing. Now we just need to know which forest produced Stradivari's spruce Hats off to expert like you and others who have worked hard for almost 200 years to uphold the integrity of Cremonese violin market. The Hill family did a tremendous job by initiating serious scholarship in this area. Their selfless passion and enlightened mentality are shining beacons from the dark world of antique trade in the 19th century. Bravo.
  21. Peter, I know some experts are capable of deauthenticating some of the Stradivari violins out there. With dendrochronology, it gets even easier. But people don't go public with this kind of information, do they? I am not saying that we should publicly de-authenticate Stradivarius violins. That would create too much chaos and hurt feelings. It won't do the world much good. Is it possible that 20% of the "certificated" Antonio Stradivari violins are not genuine? I have no idea. In the antique market, we can have situations where 95% or 99% of the stuff is not genuine. The antique Chinese jade and porcelain markets are terrible that way. The antique violin market is running amazingly well in comparison, thanks to many experts who worked hard to keep it orderly.
  22. Now imagine the reverse: Deauthenticating Stradivarius and Guarnerius violins, one at a time. Scientifically plausible. But it will make many enemies and hurt many feelings. So unlikely to happen.
  23. Did I miss something here? f1 = ?? Hz; f2= ?? Hz. I don't even know what f1-f5 really corresponds to. What modes are they? Where is the data? How can this be data-driven when I can't figure out what actual data they are feeding into the AI? The data they feed is simulation data calculated using finite element model. Nothing really measured. I am not even sure their calculated f1 corresponds to real measured values. A very confusing paper for me.
  24. I am no expert on dendrochronology but I am under the impression that matching two boards to the same tree can be done quite confidently. However, matching a board to the master chronology of an Alpine region is much more tricky. We do not have master chronology for every region of the Alps. Still, it is interesting that the Guarneris match best to the spruces from Trento. Val di Fiemme now claims to be the forest that supplied Stradivari, and it is very close to Trento. Maybe someday we will know for sure where the Cremonese got their alpine spruce. Right now we are almost certain that it came from the Italian Alps. Dendrochronology will eventually give us the answer.
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