uguntde

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Everything posted by uguntde

  1. this would rquire to wash the wood and see a tiny change in pH of the wash solution. You can't use a pH meter on a surface.
  2. I am still looking for a bow on which I get an up and down-bow staccato the way Ivry Gitlis had it . Too bad I can't get there. I also once had an interesting experience in a restaurant in Budapest. A group of musicians came in to play some music, they played Czardas among other things. The lead violinist played in amazing virtuousity, a viola and accordeon accompanied him. We started to talk and I also played few notes on his instrument and bow - the bow was worthless, a stick far too weak for anything, for me impossible to make a sound let alone play staccato. But he was so adjusted to
  3. It lacks depth, like some German wine .
  4. What do you see as typical Saxon elements? Is the prufling in any way typical for a Saxon?
  5. Most amazing about Roger Hargrave is his scientific approach and his ability to describe what he does and how. With this alone he has left a legacy. I have seen one of his instruments which was also very nice, both in workmanship and sound.
  6. I have seen two Unsworth violins, which I also had a chance to play. Both good instruments with a great sound. Here you can see one: https://www.isabellesviolins.org/unsworth/, good making, but nothing that others couldn't do. I am not fond of his varnish, but this is a matter of taste. For violas and UK I have seen many by William Piper which had an amazing tone.
  7. With violas we see a new taste in instruments that are more than just orchestra background noise. The viola suffers from an unfortunate geometry. Unlike the cello the body is too small and the fingerboard too short. If you play on the higher A string it sounds forced, and on the C it is often nasal. It is unlikely that the viola will ever reach the grandeur of the cello, it just has unfortunate dimensions.. Many makers tried to improve the viola. If you go to the instrument museum in Brussels you can see lots of Vuillaume's attempts of a mix between viola and cello. None of them survived.
  8. Are you sure this is not dirt building up? There is no good reason why a black colour (massive absorption) should develop - at least I can't see this at the moment. In some of these Southgerman instruments the black colour is caused by the use of dichromate which is a massive oxidant. Theer the surface of the wood turns black. For which makers have you seen this blackening?
  9. Depends what the solvent is. Turpentine (alpha-pinene) won't give you a lot of fluorescence. I don't know what other solvents you use. Oils won't evaporate.Oil varnish drying is not an evaporation process as is the case for spirit varnish. Try oxygen-free and oxygen-loaded linseed oil. Oxygen is known as a flueorescence quencher.
  10. Fluorescence stands for a spontaneous emission of light after light exposure, whereby the emitted light has a longer wavelength than the original light source. I.e. you shine blue UV onto the varnish and it emits visible light, or you shine UV in freshly washed clothes and you get a white visible light. Fluorescence can be quenched, in varnish, a well-known quencher is oxygen (this quenching effect is used in oxygen sensors). Once all oxygen has been used to cross-link the lipid chains it is chemically bound and the remaining conjugated double bonds will show fluorescence in absence o
  11. You must be wrong according to Sherlock Holmes who traced a crime by using fluorescing linseed oil. https://bcachemistry.wordpress.com/tag/sherlock/ My assumption is that abetic acid esterifies with the glycerole from linseed oil, and this is what happens when we cook varnish. This process alone is known to make a varnish (see lipid reactions lecture). The fatty acids in lineseed oil then get polymerised when varnish dries as explained in the Sherlock article. There may also be other sorts of reactions which are UV light rather than oxygen induced cross linking (after all violin varn
  12. Oxygen dried linseed oil would keep some double bonds which are required for fluorescence.
  13. Dear Michael I think this generally makes sense. I think Woodhosue got an unlucky spot with some minerals underneath the varnish. Maybe Stradivari used some minerals for sanding and some was left. I can't see why you think a lye would make a difference. Echard also used GCMS to proof the presence of the rosin compounds. THe results are conclusive. I still wonder whether he picked up soem left-over monomers, but then he thought about this and used PyGC-MS. The pyrolysis is to break down polymers - a dirty process though.
  14. These are good points. In the polymerisation process not all fatty acids get cross linked. One of the 3 fatty acids from linseed oil, oleic acid, won't do much at all. This means there are fatty aicd molecules embedded in the polymer. This may be the reason for the optical properties of these varnishes. With FTIR I would assume to see the polymer and the free fatty acids. With GCMS one will only see the free fatty acids, the polymer will neevr go up that GC column. What Echard measured with GCMS is therefore probably the free fatty acid content of the polymer.
  15. If you add add a siccative it will even dry fast. These siccatives (e.g. cobalt) simply work as catalysts for oxygen induced polymerisation. This is described here https://en.wikipedia.org/wiki/Drying_oil In the UK gun stock makers used to varnish with just linseed oil. I am however still not sure whether violin varnishes are air dried or light dried as all violin makers use light boxes. Probably a mix of both. Can be measured by weight change - hgher weicht means oxygen induced polymerisation.
  16. It is correct that moisture in methanol is a problem. You can of course buy 99.9% methanol but this a lot more expensive. Particularly during the pandemic it has become hard to get a hold of pure ethanol. Isopropanol is indeed much better in that respect. I have made spirit varnishes with iso-propanol and some makers like it better. You need to be quick with the brush if you use isoprop. Among unbranched molecules longer does indeed mean higher boiling point. But the iso does the trick to lower the bp.
  17. How did they blacken the wood? Lots of dichromate?
  18. It dries just by evaporation of the solvent. Use isopropanol and it will dry faster. The problems with getting hard seem to arise from esterified components of the shellac which you avoid by using a good quality shellac and by dissolving it fresh every time. http://www.michaeldresdner.com/how-and-why-does-shellac-go-bad/
  19. Echard's works on violin varnishes are scientifically among the best I have seen. There are two more I know of. But he never bother to quantify the oil/rosin ratio. Figure 4 in the Angewandthe paper sheds light on this, but peak intensities in GCMS are not particularly quantitative without proper calibration. Nevertheless, if you add all the peaks marked with a round dot vs the P, O and S it looks like a oil/resin ratio of 3/2. It is however possible that his GCMS only measures the unpolymerised parts of resin and drying oil. If drying leads to cross-linked products they would not show up
  20. 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.
  21. 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.
  22. I ask questions as Iook at violins out of interest, this doesn't mean I want to bid.
  23. 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.br
  24. These are very beautiful fittings and they make these nice gold ornaments.