uguntde

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Everything posted by uguntde

  1. 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.
  2. uguntde

    Can anyone help translate/read this?

    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.
  3. uguntde

    Can anyone help translate/read this?

    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.
  4. uguntde

    Can anyone help translate/read this?

    Maybe he means that he replaced the front, looking at the front as a Deckel?
  5. uguntde

    Violin ID (again)

    Where would the red varnish drops on the inside come from? It doesn't look as if the varnish had been sprayed on.
  6. 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.
  7. uguntde

    Removing shellac overvarnishing. Help!

    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.
  8. uguntde

    Tool rust advice

    Vinegar will cause a disatser for some metals, please be vareful. Phoshoric acid works. I would get car rust remover.
  9. I thought Austria just offered the Tyrolians citizenship, so what's the difference?
  10. uguntde

    Thoughts on this interesting violin? n

    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 .
  11. uguntde

    Purpose of tuning the fingerboard

    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 identify how it shifts A0.
  12. 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.
  13. 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.
  14. 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.
  15. 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?
  16. 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.
  17. 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.
  18. 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.
  19. 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.
  20. 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.
  21. 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.
  22. uguntde

    Oil Varnish

    Or to catch birds.
  23. 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.
  24. uguntde

    Scroll eye question

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

    Spool Clamps

    I made some of a broom stick .