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John Harte

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  1. 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.)
  2. 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....
  3. 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....
  4. 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.
  5. Michael, I am very interested in hearing more if you are willing to share.
  6. Further to my earlier post, “Violin Varnish and Coloration” by Martins Roberts Zemitis should have been included in the list of books. This book includes extensive discussion of amber, amber varnish recipes and the making of amber varnish. While Geary Baese has mentioned the presence of amber in old Italian varnish (See VSA Journal Vol.8, No.3, pp.49-73 ), as far as I am aware amber has not been identified by Echard or Brandmair in any violin varnish. Having said this, it is difficult to know what researchers might have gone looking for. Succinic acid is often mentioned as a marker for Baltic amber but, as Michael Szyper rightly alludes to, this is highly unlikely to be present in any amber varnish especially if cooked in an open pot. (The boiling point of succinic acid is only 235ºC, well below the temperature required to run amber.) Δ 8-isopimaric acid currently seems to be the go to marker for amber, but, as mentioned in the pages posted by charliemaine, this is extremely difficult to detect due to its presence being readily masked. I also have no idea how stable this acid is at temperatures needed to run amber... I have made a number of amber oil varnishes, most of which I would consider usable. They are not overly difficult to make once you understand the beast but you do need to be VERY careful and highly aware of what can go wrong!! Amber varnishes can have interesting optical characteristics which can be helpful, especially in grounds. They fluoresce a floury yellow under UV if prepared in certain ways. These also seem a useful tool should you want to push the sound of your instruments in certain directions. Were amber varnishes part of varnish systems used by Italian makers during the period 1500 – 1750? Who knows??? It seems the jury is still out..
  7. I guess a place to start is to list a few sources for amber varnish recipes. I suspect the pages featured in charliemaine's post are from the book “Lost Secrets of Flemish Painting” by Donald C. Fels. (If so, his appears to be a later edition than mine.) This is an excellent book. Included is an English translation of the De Mayerne Manuscript, B.M.Sloane 2052. A number of amber varnish recipes are presented and discussed, some of Italian origin and some specific to instruments, e.g., “The True Varnish For Lutes And Viols”. “Classic Italian Violin Varnish” by Geary L. Baese contains a number of references to and recipes for amber varnishes sourced from various manuscripts. Of potential interest here are books such as “Medieval and Renaissance Treatises on the Arts of Painting” by Mary P. Merrifield and “Methods and Materials of Painting of the Great Schools and Masters”by Sir Charles Lock Eastlake. Also of potential interest is material presented here: http://www.jamescgroves.com/germanambervarnish.htm Amber has been available throughout Europe for centuries. See: https://en.wikipedia.org/wiki/Amber_Road Gundel Steigenberger's Ph.D. Thesis titled “The Vigani Cabinet – Analysis of historical resinous materials by gas chromatography - mass spectrometry and infrared spectroscopy” is worth reading. The full thesis can be downloaded here: https://tud.qucosa.de/landing-page/?tx_dlf[id]=https%3A%2F%2Ftud.qucosa.de%2Fapi%2Fqucosa%3A27013%2Fmets Click on Volltext (PDF) at the bottom of the page. Amber, sandarac and copals are amongst the resins that were found in the Vigani Cabinet. (This is a collection of 300-year-old pharmaceutical and chemical materials owned by Queens’ College, Cambridge, UK.) @Michael Darnton, you may want to skim through the Summary (pp.7-11) and see whether this might be of interest. More to follow...
  8. These are excellent posts! Thank you both. I'll try to post something in the next day or so.
  9. Jackson, thank you for your reply. Colophony presence doesn't necessarily exclude amber or fossil copal presence. Fossil resins in varnish or paint films are notoriously difficult to detect. I have seen it mentioned that whatever is in the wood is more resilient than upper varnish. If(???) this is indeed so, might it suggest the involvement of something other than merely colophony varnish? I'm not advocating the use of fossil resins, just that the jury may still be out regarding their use/non use. If this is worth discussing, might it be worth starting another thread?
  10. Could you please say more regarding the lack of historical relevance you mention. I am yet to see conclusive proof that supports the non use of amber and/or fossil copals in classical North Italian instrument finishes.
  11. Steve, thank you. I'm looking forward to reading this.
  12. I have been worried that someone would ask me this... As I have mentioned this happened a while ago. I still have all the samples in a box somewhere. Notes may also exist but I wouldn't know where to begin looking for those. What I do recall is a small glass petri dish that would have contained no more than 10ml of ammonia being placed in the bottom of a screw topped closed glass jar which I would guess would have been around 1.5 litre volume. Each of the two fumed samples were suspended in the jar using some sort of thread (cotton, linen, polyester??? Probably whatever I was using for bow rehairing at the time..) The mild fuming would probably have been around 1 to 2 hours and the long term upwards of 12 hours. It could have been a day or two. The ammonia was bought from a chemical supply company and is described in a list of chemicals that I have as “strong ammonia”. Having said this, this bottle of ammonia was periodically opened outside for short periods over the years for the purposes of fuming boxwood peg shafts so would likely not be as potent as it originally was. I see in amongst the microscope photos a sample recorded as NH3 + heat. I am guessing that this was an attempt to get rid of the residual smell of ammonia or maybe add a more complex colour aspect to the spruce. I have no idea of how much the heating may have impacted the ammonia reaction, both in the short and long term.
  13. This may be of partial interest: https://heritagesciencejournal.springeropen.com/articles/10.1186/s40494-022-00718-1 Also note the Supplementary Information. Without reading this again I can't tell you whether there is any discussion of full reaction time.
  14. No. My focus at that stage was more related to possible full wood treatments and their effects; i.e., various forms of full immersion soaking (long term water, borax solution, boiling), fuming (ammonia, ozone) and heating/baking. I have tried nitrites (Na and K) but only in the context of trying options that could colour/stain/darken wood surfaces.
  15. Thanks for all of the comments regarding the photos. A few extra comments follow that will no doubt add more confusion... Paul, ozone treated wood was another that I looked at and have photos of. I did not consider nitric acid. At the time I had spruce and maple that I had applied nitric acid to surfaces of but nothing that had been fully immersed in nitric acid. Don, I agree with your observations and reservations. All I can say is a relatively clean cut on the end grain face of the untreated Norway spruce sample featured in the first photo was reasonably easy to achieve. (FWIW, other untreated spruce samples from a different source were similar.) Mild ammonia treatment resulted in increased difficulty in achieving a clean cut with some tearing being evident. Longer term ammonia treatment resulted in even more difficulty. During the cutting process some cell walls crumbled or collapsed. I used fresh blades in each case and did my very best to create as clean as possible endgrain surfaces. This involved using a slicing as opposed to pushed cut which I did vary depending on the inherent nature of the sample involved. Some samples were quite brittle, others more crumbly, some firm, some soft and soapy etc., etc.. A clean as possible cut was my primary goal for the reason mentioned below. Michael, I also looked at spruce samples that had been heat treated in various ways. In some cases the end grain cut achieved was very clean and crisp and in others, not so. Davide and Don, my somewhat misguided original intention was to look at cell wall detail in various treated samples and compare the detail to that in old wood. Don, like you I had some old spruce from buildings. (I think yours, like mine, is a dendro match to certain Cremonese instruments???) I also had spruce taken out of an old German piano. I felt that SEM would likely provide a means of seeing what remained intact versus degraded within cell wall layering which in turn could provide some indication of whether lignin, hemicellulose or cellulose had been impacted. (Note diagram below.) The initial step involved preparing end grain surfaces and viewing the various samples under a stereo microscope. It was immediately evident that the end grain in most samples was not cleanly enough cut to guarantee seeing the cell wall layering detail that I had hoped for. At that stage I forgot about SEM and decided that all I could do was to take photos of the cut detail through a more powerful stereo microscope. As to what these photos actually mean – I suppose that in a very loose way they may suggest that some treatments seem to impact cell wall integrity/strength/resilience more than others....
  16. The following may add to the various comments posted so far. Around 7 years ago I took a number of treated wood samples into a microscope laboratory at a nearby university. The photos below are cropped out of shots taken through a microscope capable of up to 500x magnification. The first features untreated spruce cut in 2013, the second, spruce that has undergone a mild ammonia treatment and the third, spruce that has undergone what I have noted as long term ammonia treatment. Each end grain face was carefully prepared using a new razor blade typical of those used in laboratories for preparing as crisp as possible detail in such samples. The increasing lack of crispness with increased duration of ammonia treatment suggests that ammonia treatment does degrade/weaken cell wall structure. Note cell wall collapse (upper left side) in the third photo.
  17. Thank you Jackson and Daryl. Much appreciated!
  18. Jackson, thank you for your reply. Like Davide, if you are willing to share, I would like to hear more about the casein glue you use.
  19. Jackson, thank you. This all makes very good sense, at least to me.. Do you use anything other than casein glue to hold the neck in place, for example, some form of screw through the top block into the neck? I would imagine that if you were nailing the neck, as was the case in Cremona, this would ideally be done at the same time that the neck was glued, or maybe not???
  20. You make good points. I have never made a baroque style violin but have always assumed that the neck would be attached to the rib structure prior to either the back or top being attached. As you point out, planing the neck root to achieve a perfectly flush fit against the back button would require skill given the spindly nature of the rib assembly. Having said this, Roger Hargrave seems to think that this is a relatively easy task. (See p.69, Journal of The Violin Society of America, Vol.10, No.1)
  21. I completely agree. Regarding neck attachment, given the type of rib taper mentioned, distortion resulting from attaching the top first could potentially necessitate a steeper initial neck set than if the back was attached first. Top first might require more best guessing than a back first option. I suspect that makers like Strad were fairly pragmatic when it came to such things.
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