uguntde

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Everything posted by uguntde

  1. uguntde

    Oil Varnish

    Chemists would use an electrical heating mantel. But this does not distribute heat evenly, nor does a sand bath. You also need a magnetic stirrer to keep temperature exposure more even. All of this seems an overkill, I can't see classical makers using anythong but a wood fire, maybe an oven, but without any temperature control.
  2. uguntde

    Oil Varnish

    The melting point of abietic acid is around 175˚C. A 'foaming point" is not a chemical property. Melting = boiling. This will be lowered by imputities (ebullisocopic propertes). If you slowly change colour you get all kinds of oxidisation products, unlikely carbon. If you really burn it you end up with residues of what is there besdies abeitic acid and some tar like long chained products, besides CO2 (in the presence of oxygen). Some slowly oxidised rosin can have very desirable colours for varnish. If I ready Hargrave's bass article correctly he colours his varnish just this way or by adding a little nitric acid. However 200 ˚C is certainly enough for all of this.
  3. uguntde

    Oil Varnish

    I think the darkening of the colour is a kind of burning the rosin. I can't see an oxidisatino process that would change the colour in the same way. The burn fraction is probably small and may have a desirable effect on colour. But some of it is probably not abietic acid any more.
  4. uguntde

    Choice of linseed oil

    Linseed oil comes in many varieties. Apparently the sun-bleeched refined (73300 Kremer) is believed the make faster drying varnishes. The also offer cold pressed (73054 Kremer Linseed Oil). And there are many others on the market. Does the refined oil still require 2-3h of cooking?
  5. uguntde

    Choice of linseed oil

    I compared Kremer refined linseed oil with a food grade cold pressed oil from ebay (https://www.ebay.co.uk/itm/Linseed-Oil-Pure-Food-Grade-50ml-1ltr-100-Cold-Pressed-Unrefined-Flax-FREE-P-P/202255083645?epid=5017655496&hash=item2f1757a87d:m:mBRyrd7gby4P0W5qFrK6y9Q&var=502218492010) they both dry. The latter I washed with water for several weeks. I will soon qualitatively compare drying times.
  6. uguntde

    Choice of linseed oil

    Oleic acid does not have conjugated double bonds (it hly one double bond, see picture from wikipedia). It will not contribute to the drying process as it can not crosslink. An oil high in this component (this could be envrionmentally influenced) would stay 'sticky', i.e. rich in unpolymerised components. I don't know what happens to oleic aicd over time, or whether it gets oxidised (more double bonds) when it is heated.
  7. uguntde

    Violin making in the Graftschaft Glatz

    Is this Jacob Weiss related? https://www.bromptons.co/auction/25-june-2018/lots/95-an-austrian-violin-probably-by-jacob-weiss-salzburg-1777.html This was an interesting violin.
  8. uguntde

    Choice of linseed oil

    Well, some of this may have been discussed before, but many questions also remain unanswered. I am not a vaarnish expert, but this is my underdstanding from reading up some of the chemistry. Linseed oil is like any oil a glycerol ester with three fatty acid groups: linoleic acid, alpha-linolenic acid, and oleic acid. Two of them have conjugated double bonds (linoleic acid and alpha-linolenic). When we cook varnish we cook with with abeietic acid, which also has a carboxylic acid group and conjugated double bonds. When we just cook linseed oil we change the arrangement of these conjugated double bonds, as it seems for the better. More conjugation = better drying. When we cook linseed oil with a base or an acid it will get saponified, i.e. the ester bond between the carboxylic acid end group and the glycerol gets split. As product we get glycerol and theree fatty acids. If we now cook with abeietic acid we can esterify the same with glycerol and get abeietic/inoleic acid, alpha-linolenic acid, and oleic acid mixed glycerol esters ( glyceryl abietate or ester gum). The longer free fatty acids will in this mixture act as solvent for the ester gum. This is why the reaction between rosinate and oil goes vigorous and faster with ash water and lime - this acts as a base catalyst for the esterification. In my experience it goes even faster with a frop of acid. I saw a massive exothermal reaction with both. When we expose to light we get a reaction between our fatty acids and fatty acid esters with conjugated bonds with each other. This is a light induced so-called Diels-Alder reaction (a common chemical reaction, the can be light or heat induced leading to a different stereochemistry). The outcome is a complex cross linked structure. This happens during the process of hardening. The same can of course also be done with just the two fatty acids from linseed oil that have conjugated double bonds - this is why this will also dry. But having 50% of extra material that can be cross linked helps, and the abietic acid structure will also give a material with a higher boiling point. There is a huge body of literature about this, a lot of it buried in old patents. I should say that I am an analytical chemist, but know not much about polymers and varnishes. Some of what I just wrote is guess work based on basic organic chemistry, but I did read a few articles when I folloed the discussion about UV photography (conjugated double bonds absorb UV and show fluorescence). Happy to be proven wrong, maybe there are other chemist out there in the violin world and we get some discussion about what these varnihes are. I have also recently compared differnt linseed oils and I may carry out some chemical analysis to find out what happens when I boil the oil. I m ay report the outcomes at a a later time. My main interest was drying efficiency.
  9. uguntde

    Choice of linseed oil

    The practice of sun thickening of linseed oil is very old indeed. Strad may very well have used refined oil, just with the methods available then. Abour Kremer I read somewhere that they have someone in the Alps who sunthickens oil for them in large flat metal containers. I assume this is what they sell as refined linseed oil.
  10. uguntde

    Choice of linseed oil

    I just realised that this topic has been raised before. But I am motr interested in what people are using.
  11. uguntde

    Oil Varnish

    Or to catch birds.
  12. uguntde

    Mittenwald Violin

    I haven't seen these f-holes in any Georg Kloz. Georg Kloz violins also are more rfined than this one. But is seems to be a decent Mittenwald violin but needs indeed a lot of work. Whether you can get these cracks properly repaired I doubt.
  13. uguntde

    Scroll eye question

    So is this also a 'bad' scroll?
  14. uguntde

    Spool Clamps

    I made some of a broom stick .
  15. uguntde

    Interesting or not ?

    Also a great recording of the Shostakovich viola sonata by Sara Kim on youtube, on Paolo Antonio Testore. Not sure this is the same Testore as Bashmet's viola. Nevertheless, this who business of scratched-in purfling and ugly scrolls is a sign of fast sloppy making of the instruments, not the best workmanship. This doesn't mean the sound was not good.
  16. uguntde

    Interesting or not ?

    Testore violins would certainly not win any competitions today, and some of the scrolls a re really ugly. Some violas from that family have an amazing sound though. Overall I think many Testore family violins with painted-on purfling are not really nice workmanship.
  17. uguntde

    Another violin ID quiz

    Maybe this would deserve a new thread, but I often wonder why people spend 20-30-40k for a new violin when they can get an old for the same or less. There are also modern makers who make great instruments for less. My favorites in the last Tarisio sale were the ASP Bernardel and the Hel (the latter with a bad button repair). Both will have an excellent resale value and great sound. Whether a new violin retains value is very questionable. Maybe a new fiddle has sound optimisation, is as good as a Strad or better in a blind test. But whether it carries in a concert hall most players will never experience. Orchestral players could just as well use a good sounding Chinese, and nobody would notice. For chamber music other tonal qualities count, beauty of sound is not always carrying power. For example, a good Kloz can be excellent for quartet playing. I am sure there is lots to argue about in these lines. I really appreciate excellent modern making, but I would never pay that premium for a violin that I can never sell again. Nevertheless, that market of above 20k violins seems to be doing well.
  18. uguntde

    Does anyone NOT build Strad? And if not, why?

    I really liked the tone of the Stainer in the last Tarisio auction in London. Has anyone else played it? It was on the same table as the Oddone and the Fagnola, although much nicer in tone.
  19. uguntde

    Mittenwald Violin ID

    It is hard to distinguish any different makers but Kloz from the Mittenwald school. Even with the early Hornsteiners it can be difficult without label, because they worked with Kloz family members. Many of those German makers put in wrong labels, Kloz family members took Stainer labels, and later others used Kloz labels. Regarding Italian violins I remember a Guarneri in an auction a few years ago with a Hamma certificate, which was proven not to be Guarneri by dendrochronology (probably a Voller Brothers).
  20. uguntde

    Mittenwald Violin ID

    To get some sense into this: how do you distinguish Hornsteiner from Kloz violins when there is no label? Is the U-shaped insert in any way typical? Also strange to replace a back with one with the U inserted, why not make a proper one? Maybe a secret signature from? As a general rule I find that violins of this kind (German 18th century) without label are almost impossible to authenticate. Although, this one actually has a label. With 'The German experts seem to accept this as Kloz' I meant solely the varnish, which is not the typical water soluble stuff. It seems to be accepted that this type of varnish appears on Kloz violins. They seem to have used different types of varnish.
  21. uguntde

    Mittenwald Violin ID

    Not to or not too?
  22. uguntde

    Mittenwald Violin ID

    The Kloz family varnishes vary. There is this famous glue varnish which is water soluble. But you also find other varnishes, like the one on the violin depicted above. The German experts seem to accept this as Kloz.
  23. uguntde

    1759 Gagliano Pawned for $50

    I met someone a few years ago who bought a G Bernardel in a Menesson case for something like €30 at a flee market. It was undoubtedly genuine although not strung up. Such things do happen.
  24. uguntde

    Superglued crack on a violin?

    I don't know how well Aceton works but I can confirm it is completely harmless.
  25. uguntde

    Turin blockology

    I have seen this striped paper in some French violins. Does anyone know what it is?