uguntde

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About uguntde

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    https://www.birmingham.ac.uk/staff/profiles/cancer-genomic/gunther-ulrich.aspx

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    Birmingham UK
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    Science, NMR, string instruments

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  1. The Bernardel disappeared some time during the auction.Can they do this, just withdraw? I assume the owners changed their mind or there was doubt whether it was genuine.
  2. I have seen a few violins without value with a great sound. This one sounds great in the hands of this player, even though it is a factory made instrument. I once heard a Hungarian band in a restaurant in Budapest. I then also played a few notes on that fiddlers violin and was disappointed, he had a very simple violin. His bow was even more awful, no strength in the stick. But he was completely adapted to this setup and played a super fast Czardas really well.
  3. I ask questions as Iook at violins out of interest, this doesn't mean I want to bid.
  4. Can I ask for several opinions at one time: Frederick Daniel Mahoney - is he known to any one else? It looks interesting. https://www.bromptons.co/auction/22nd-june-2020/lots/132-an-english-viola-by-frederick-daniel-mahoney-london-1937.html The Bernardel viola (they had this already in the last auction): There are a lot of typical features but some are not Bernardel, the scroll is very untypical, and I hae never seen this varnish on an AS Bernardel. The edge work work of the front is also not typical, and the choice of wood for the front is irritating. https://www.bromptons.co/auction/22nd-june-2020/lots/136-a-fine-french-viola-by-auguste-sebastien-bernardel-pere-paris-circa-1840.html After Gaetano Chiocci: https://www.bromptons.co/auction/22nd-june-2020/lots/137-a-viola-after-gaetano-chiocchi.html Looks interesting, but what is it really? Lots of repairs on this one.
  5. These are very beautiful fittings and they make these nice gold ornaments.
  6. uguntde

    Viola ID

    Who the hell is Harris and Sheldon in the Brompton highlights? https://www.bromptons.co/auction/ Is this Nigel Harris from New Zealand? Somewhat uninspiring with kind of perfect workmanship.
  7. This is way beyond what a violin maker wants to know, and I just read this varnish chemistry out of interest. From what I read I assume that adding a little phtalic anhydride would make varnish dry faster. If someone wants my literature collection on varnishes let me know, I have a lot. There is an interesting master thesis on the internet entitled MODIFICATION OF TUNG OIL FOR BIO-BASED COATING by Narin Thanamongkollit presented to the University of Akron.
  8. I am not sure it makes sense to talk about a soap in this matrix as there is no water. Also abietic acid is not a lipid. But reaction with glycerol makes an ester gum which has drying properties. The glycerol will form mixed esters ( groups per glycerole) with the fatty acids of linseed oil and abietic acid. As abietic acis is present in excess it will push the equilibrium towards its ester product. But 2 of the 3 fatty acids from linseed oil can cross link with the fatty acids from linseed oil. These reactions are well understood in acqueous solution, as used in Frye's method of making varnish. There you get a soap, and it feeld like soap before adding alumn. In the oily matrix alumn will mainly icorporate some metals. I have also added FeCl2 to get some red colour (you really want FeCl3 but it is oxidised in situ). A base is probably simply a catalyst. It makes the process a but faster. Addng metab oxides probably also catalyses the 2nd reaction, the corss linking - the process is a completely different reaction, probably involving radicals. Abietic acid is an organic acid
  9. In acquesous solution esterification (this includes cross-esterification) is base or acid catalyzed - I assume that is the same when you cook varnish in linseed oil. In my opinion what you do when you cook varnish is a cross-esterification. You remove the 3 fatty acids (linoleic acid, alpha-linolenic acid, and oleic acid.) from the glycerole, and you add some abietic acid, i.e. abietic acid replaces fatty acids on the glycerol, probably depending on the ratios. Oleic acid can not participate in the reaction and probably acts as a kind of softener. The base would work as a catalyst, speeding up this process. In some cases I belive I saw a bubbling effect when adding lime later, but this observation may be misleading, as I added it in water which may have caused all the bubbling. When the varnish hardens it is mainly the alpha-linoleic acid, but to some degree also the linoleic acid that undergo reactiions via their conjugated double bonds (probably light induced Diels-Alder reactions). This is why linseed oil hardens even without rosin, i.e. without the abietic acid. But you get better cross-linking and a harder varnish with the abietic acid, which also has a conjugated double bond. There are a lot of older patents about this from the varnish industry as they use the same principle. For industrial varnishes the hardening is of course usually not light-induced but radical induced because it is faster. But the process is a different one. If this is correct, and I admit it may not be, adding a tiny bit of KOH or carbonate should be even more effectve that adding lime to the cooking process. Lime is an odd choice as it leaves silicates and dirt that is difficult to be removed afterwards. I would be interested to hear other opinions about this.
  10. The lime is still a mystery for me. I think it is the catalyst for alcaline cross-esterification, replacing lipids with abietic acid. Am I wrong?
  11. I hope you are not insulted, but the value is that of firewood. The newspaper inside may be worth more though.
  12. In a 2018 recording on youtube he seems to play a modern viola. WIkipedia says he owns a Vatelot. Or is this the Mahler Strad you are talking about? Here he shows the Strad and it looks different.
  13. uguntde

    Viola rib height

    A while ago I studied the Guadagnini violas on Cozio. I started with Hargrave's blog on a Guadagnini he found in China. He says he lost his notes at one point, or they were stolen, but still gives a good description of that instrument. Several on Cozio had the same body length (402mm, just above 16"). The rib hight was consitently 37/38. I find violas with a powerful C string benefit from tib height up to 39/40. Rib thickness is also important as much of the C-string sound is an air resonance.
  14. uguntde

    Blanchard Fake?

    A Blanchard is very hard to fake because his workmanship was quite exquisit. If it is a fake it is easy to identify as such. Glue marks could only be from a bad repair. The difference in price tag of a Blanchard and a fake is at least a factor of 10. Whether there were others in Blanchard's workshop who made instruments and used such a label I don't know.
  15. The reaction of rosin and linseed oil is chemically a cross-esterification. Lineolic acid gets attached to abietic acid. In solution such reactions are base catalysed. I assume that something like this is happening in hot rosin, especially, as the lime is added in water. Lime light just catalyse the ester cleavage of the abietic acid. Industrially anothet catalyst is used which I need to look up. This is just an assumption, as I know little about such chemistries.