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John Harte

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  1. Mike, I would be surprised if this is not from a violin. In other places it has been specifically referred to as a sample from a 1728 Strad violin. This SEM image looks different to any published as part of the initial study which appeared in Nature, The Strad and the CAS Journal. One of the Strad samples in the initial study came from a 1711 cello rib. I don't recall mention having been made of the origin of the second Strad sample other than it being referred to as probable. Barlow and Woodhouse, Echard, and Brandmair are probably not quite as far apart as might be imagined. The actual data doesn't seem to conflict, just the interpretations. This has been discussed at length on Maestronet in the past.
  2. Mike, it seems that she also claims to have found the same in a violin. The image below is from this paper: https://www.academia.edu/89024968/Chemical_and_microstructural_studies_of_violins
  3. In the interests of full disclosure, I should come clean and mention that I often use the same knife handle as Davide with a #11 scalpel blade for cutting the bee sting point recess. My main weird looking knife was inspired by Spidlen's purfling knife illustrated in the August 2005 Strad magazine. It works well in both spruce and maple with the shape being particularly useful if you want to make a pushing cut through harder spruce grain lines etc.. I've tried lots of different options. At the end of the day it comes down to what you can get to do everything you want with the least amount of grief involved.
  4. There are probably much better options than these. I have struggled with single bevel knives, overall preferring double beveled options. This may not be the experience of others though. My current go to purfling channel knife is shown below. The blade is 8mm wide and the profile is the same on both sides. This seems to produce a tidy result.
  5. There is a reasonable amount that could apply to lutherie, depending on what you want to make sense of. For example, a study considering differences between early and latewood response to UV exposure might help someone make sense of the process that occurs with respect to darker annular rings in torrefied wood that Don has mentioned. In a similar vein, someone may want to know more regarding the lighter sap strip that is seen in some old (and not so old) instruments. Most of what I have found is not of much practical use. If one wants to photoyellow instruments using UV lights, the most significant “finding” might be to avoid anything that emits light up into the visible blue range. Mind you, it might be that some photobleaching following photoyellowing is actually beneficial...
  6. Thank you Davide. Further to my above posts, there are a number of other studies that consider the ways in which various softwoods and hardwoods, untreated vs TM wood, earlywood vs latewood, sapwood vs heartwood respond to UV and visible light exposure. If you are interested in any of this, let me know.
  7. Broadly speaking, this seems to be what ends up happening. For more, see: https://www.researchgate.net/publication/280096685_Novel_color_stabilization_concepts_for_decorative_surfaces_of_native_dark_wood_and_thermally_modified_timber While this particular study focuses on ways to mitigate photobleaching in dark woods (including spruce TMT), there is good material in the introduction that explains the various processes that occur in dark woods under UV and visible light.
  8. This paper may be of vague interest: https://link.springer.com/article/10.1007/s00226-013-0601-4 The conclusion provides a quick outline of the findings.
  9. Studies suggest that TM wood is prone to photobleaching under various light sources. As a side note, studies also suggest that UV exposure will impact differently on earlywood vs latewood and sapwood vs heartwood. It seems that lighting outside the UV range is also a player in wood colour change. Understanding the different processes involved in the various frequency ranges, and they do seem to differ, may be helpful in providing a more complete understanding of aged wood appearance.
  10. Just to add a little more to what Don has illustrated. Lighting and light direction are critical in terms of what is or isn't seen, especially on these instruments. Some shots (Titian) below will hopefully illustrate this. The first two feature spruce, the first with light along the grain and the second with light across the grain. Note what reflects light and what doesn't in each. These were taken through an illuminated magnifier. The third shot is obviously maple and was taken under room lighting. The fourth and fifth shots are maple, again taken under the illuminated magnifier with the light aligned along the grain. Unfortunately I haven't a shot of the maple with light aligned across the grain but a similar thing happens to what is seen in the spruce shots.
  11. Mike, it's good to see you posting here. I suspect that the most commonly referenced source for the identification of a drying oil ground is this 2009 communication: https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.200905131 Features are mentioned that the authors state “can be interpreted as those of a partially oxidized and hydrolyzed drying oil.” The true situation is likely more complex as hinted at in Chapter 5 of Celine Daher's Ph.D. Thesis which was submitted in late 2012. (She was a student of Echard's.)
  12. I think that this and Mike's earlier comments are well worth noting. I have tried to suggest to a couple of the Arvedi Lab researchers, including one of the co authors of this latest article, that the protein presence may not be the consequence of a discrete protein size application but rather to do with wood and varnish colouration. They are still fixated on the former but hopefully in time it will dawn on them that there are possible alternatives that may be worth investigating. On this point, their mention of clear proteinaceous hot-spots being detected in the V and P layers of the stratigraphy of the San Lorenzo could possibly suggest protein presence associated with pigmentation. Also, FWIW, I don't think that their labelled P layers are clearly preparation layers but rather more a part of the V layering. I suspect that the preparation layer may have more to do with the floury yellow material within the upper wood cell structure as seen in the UV images. It seems that the fractures separating the coating systems from the first line of wood cells may have derailed their thinking. Fractures can happen in various places within varnish stratigraphy and for any number of reasons. On the issue of contamination or not, it is increasingly possible to differentiate between various protein origins. There are some interesting recent studies that these researchers could consider in the interest of better understanding what might actually be involved. In my view, what they are currently considering is far too limited. Other clues in other publications that this group of researchers have been involved in possibly support Mike and my own contentions. Based on this article, it would seem that they may not yet have grasped the potential significance of these. Maybe one day....
  13. Yes they could very well be. Retesting both samples after a year or two would likely give some indication. Exposing the samples to an elevated humidity in the interim may also amplify any changes caused by residuals. It would also be interesting to know what the outcomes might be for different strength initial treatments. A low molar strength sodium or potassium hydroxide treatment may be close to fully expended in any initial reaction as opposed to what might be the case for higher molar strengths. I'm not a chemist so this is way beyond my pay grade....
  14. In an earlier post I mentioned this study and its Supplementary Information: https://heritagesciencejournal.springeropen.com/articles/10.1186/s40494-022-00718- Quoting from the paper, “This study aims to fill the lack of knowledge about the effects induced by chemical alkaline pre-treatments. To this purpose, reference wood samples were treated with the fuming ammonia and the potassium hydroxide pre-treatments. A multi-analytical strategy was then used to assess the aesthetic and ultrastructural transformations of the treated wood.” Long term or possible on going effects were not considered. Again quoting, “After the treatments, and to reach the equilibrium condition with the environment, the specimens were cured under monitored conditions (RH = 50%, T = 20 °C) in a storeroom for one month to eliminate the water absorbed during the KOH treatment and the entrapped ammonia.” While I have found what you could term the initial chemistry and ultrastructural transformations revealed in this study to be of interest, it would also be interesting to know what might be different after one or two years.
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