uguntde

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Everything posted by uguntde

  1. I think what they were after is the yellow colour of bilirubin breakdown products. Horse should be as good as any, as this arises from haemoglobin breakdown, and not any specific food ingredients. Whether Aubert still does this I don't know. It is my impression that most of the Chinese bridges sold in a bundle are just as good. Hardness of wood is all that is needed.
  2. I heard from someone that the pricier Aubert bridges were cured in horse urine. Is this true? If anything urea deposits would make the wood heavier.
  3. uguntde

    UV Cabinet

    I recently tried UVC 35W for tanning (2 90cm tubes) - works extremely well. Just need to switch it off before opening the box, as UVC damages about everything on the human body.
  4. Makes some sense as the last letter of that name could be an ü. Hath..ü, could also be Häth zu Karlburg. The name Johann is as German as it gets, but also known as a Hungarian name. http://magyarnevek.com/nevek/ferfinevek/J In their list starting with H http://magyarnevek.com/nevek/ferfinevek/H nothing Hungarian suits your label.
  5. But there is no squiggle over u in Karlburg and the letter in the na,e looks clearly like an a. Hath or Häth. Admittedly, this would be a strinage sounding name though. The script is also not a cear altdeutsche Schrift, but a mix of the same and Druckschrift.
  6. Maybe he means that he replaced the front, looking at the front as a Deckel?
  7. Where would the red varnish drops on the inside come from? It doesn't look as if the varnish had been sprayed on.
  8. There is now a Facebook group to sell violins ... trying to look more serious than ebay. What I have seen there was massively overpriced or rubbish.
  9. Rub the new spirit stain stuff off with ethanol or isopropanol, hoping that the varnish underneath is not spirit soluble. Even an old spirit varnish will not come off easily. But you can make a terrible smear with this method, you may also be lucky. Otherwise there is probably no such thing as fine grit sand paper.
  10. Vinegar will cause a disatser for some metals, please be vareful. Phoshoric acid works. I would get car rust remover.
  11. I thought Austria just offered the Tyrolians citizenship, so what's the difference?
  12. The fittings are old English fittings, probably made of holly. I see these pegs a lot on in England. Scratched in purfling is typical for some simpler 19th century English instruments. The scratch marks may have been done by a kid who was bored by practicing .
  13. I have a really good sounding viola. It is made very light, with a light fingerboard with reduced thickness (many Degani violins have this). If I don't touch the neck the open A has a strong wolf. As soon as I touch the neck this is gone (this is why it took a while until I noticed that interesting feature). I then experimented with small weights - I used roofing lead with doublesided tape - to tune this fingerboard. And with an extra 2g of weight the wolf disappears. The overall sound character is not much influenced though. I can try to get a spectrogram with and without the lead to ide
  14. 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.
  15. 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
  16. 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.
  17. 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.
  18. 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.
  19. 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.
  20. 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 c
  21. 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.
  22. I just realised that this topic has been raised before. But I am motr interested in what people are using.
  23. 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?
  24. 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.