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John Harte

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  1. Steve, thank you. I'm looking forward to reading this.
  2. 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.
  3. 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.
  4. 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.
  5. 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....
  6. 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.
  7. Thank you Jackson and Daryl. Much appreciated!
  8. 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.
  9. 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???
  10. 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)
  11. 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.
  12. As you say there are some good arguments for attaching the top first. However, if you reduce the rib height from the upper corner blocks to the upper block on the top side as clearly seen to be the case in CT scan images of the Messiah Strad, might attaching the top first work against this remaining the case? Attaching the back first would be more likely to retain what appears to exist in the mentioned CT images; i.e., the reduction in rib height clearly having remained on the top side. Furthermore, given the way in which the rib height reduction has been achieved, might not attaching the top first introduce greater variation in top and back outlines than we typically see? (I am assuming here that respective outlines were derived from the rib outline as opposed to some template.)
  13. Filippo, your situation sounds similar to mine 40 years ago, although today you have the internet and, even better, you are in Italy! There are some specialist tools that you will have to buy but much of what you will require over and above what you seem to already have, can be made in some form or another. Closing clamps, bassbar clamps, lining clamps, some sort of purfling scriber, a thicknessing/graduation punch, a glue pot, a peg shaper etc., can all be made. Thinking back to what I bought in order to make a first violin, I would suggest gouges (in my case 7mm, 10mm and 16mm – all 5 sweep), thumb planes with both plain and toothed blades (I bought 25mm, 30mm and 36mm but you could probably get away with the smaller two of these), a small plane (e.g., Lie Neilsen 102 or well made block plane), a peg hole reamer, scraper steel, various files, a soundpost setter, a fret saw and coping saw, a purfling chisel, and some sort of knife. In my case I used a small Stanley knife and several packs of blades of various shapes. These are probably no longer available but there are now plenty of options available in craft or art supply shops. I made my own bending iron which worked for the first violin but subsequently ended up buying a commercially available iron. There are no doubt things that I have forgotten... After making my first violin I bought a one way airline ticket and headed to the northern hemisphere to find out how real violin makers made violins. As I have mentioned, today you have the internet and are now able to see how various makers approach various tasks and what tools they use and how they use them. Davide Sora's videos are superb. Every one is worth studying. I wish that these were around 40 years ago!!!!
  14. Don's comments are excellent. I use a 1500 watt cooker and generally a sand bath. Even then I have to be mindful of the depth/amount of sand used in the sand bath. Too much results in having to wait for an unacceptably long time to reach temperatures that I might want. For a number of reasons I also use a temperature controller of the type that Don suggests.
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