uguntde

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Posts posted by uguntde


  1. 10 minutes ago, Felefar said:

    So it could be a Hungarian name then, with or without faded letters - Hathory? Halh... 

    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.


  2. 2 hours ago, jacobsaunders said:

    Since old German „U's“ have a line or squiggle above them, to help differenciate between all the vowels, one may say with confidence that the name is „Huth“ (i.e. Mr Hat)

     

    An almost certainly frivolous thought came to me, since the South German colloquial „Deckel“ means belly, so that with the prefix „Ge“, this would make it into “bellied” which makes one think of the frightful Ebayspeak like “Blocked” or “Cased”. I know that this is improbable, but it would still wake a reflex in me, to check if the instrument has it's original belly or not.

    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.


  3. 19 hours ago, Andreas Preuss said:

    Looks like old Gernan to me:

    Gedeckelt von Johann / Hulb (or Halb) in Karlburg/ 1720

    In old German 'gedeckelt' means to close a lid. If the writer meant by that that he made the instrument is not entirely clear. At least I don't know any violin maker by the name Halb or Hulb. 

    Karlburg seems to be a village at the main river.

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


  4. 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.


  5. 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.


  6. 4 hours ago, David Burgess said:

    Yes, in my own experiments. No, not the same hardness as some resins, or glass.

    Yup. Hot spots can take localized temperatures way above those measured with a thermometer. These can be reduced by using a very thick pot which spreads the heat more evenly, or using a sand bath. My current method is to heat evenly from all sides using an oven.

    Warning: You will need a "chimney" to extract the volatile exudates, because they can catch fire or explode. 

    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.


  7. On 9/17/2018 at 9:50 PM, Michael_Molnar said:

    You are not adding carbon to the varnish. You are oxidizing it similar to toasting bread. If you toast bread too far, you turn it into carbon and it looks, smells, and tastes terrible. Burnt varnish has black opaque clumps that destroy the varnish. Cooking pots that have hot spots on the bottom are notorious for burning. 

    IIRC, the foaming temperature is about 390 C. Would someone check if that is right.

    Roasting rosin is at a much lower temperature, a little above 200 C. Again, someone should check my figures. 

    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.


  8. 9 hours ago, finnfinnviolin said:

    Right, but I have cooked colophony in two different ways, one at low temp, one at high, the one at high temp has to be sat on a shelf for a year or so so that the crud and carbon particles sink to the bottom, what I’m saying is that this seems pretty high to me, and I wonder if cooking this high when getting to the pill stage could possibly burn your rosin. 

    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.


  9. 23 hours ago, David Burgess said:

    Health food store sources of linseed oil, and artist supply sources can be very different things. We want them to dry,  and the "health food" industry doesn't.

    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.


  10. 23 hours ago, Danube Fiddler said:

    While I can´t contribute to the chemical things, you just described - I assume, there could be two partially independent things : a) drying and b) loosing stickiness.     In my experience oil can dry quite a lot, but can stay sticky. My idea is, that the reason could be a certain critical component of the oil, which must get removed or destroyed. This component could be any substance soluble in fats and regularly existent in most kinds of plant-oils. 

    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.

    512px-Triglyceride_unsaturated_Structural_Formulae_V2.svg.png


  11. 23 hours ago, Blank face said:

    Thank you for recalling this most highly interesting topic! (We mentioned it from time to time before)

    For comparison are here some photos of a violin by Vincenz Beck, prob. Johann Georg's son (same name with different spelling) and by Cajetan Weiss (I've got the photo of the front only), a widely unknown maker from this region. I found him mentioned as from Kislingswalde (as written on the label), a different town, but see no reason to doubt the signature.

    Both are demonstratting in my eyes the countinuity and idiosyncracy of the local models and traditions.

    The V. Beck was constructed in all aspects like Jacob described, the f nicks have a distinctive unaltered form. It has a large body size of 365 mm, I'm assuming that this is typical for the whole school.

    It shouldn't be suspected that instruments of this origin were considered of low value. I got mine with a nice Knopf bow in a former surely valuable, but unfortunately very rotten leather scabbard with a document indicating that it was once before the property of a certain "Herrn von Unruh, Kgl. Music Dirigent" (musical conductor of the king).

     

    IMG_0294.JPG

    IMG_0295.JPG

    IMG_0302.JPG

    IMG_0303.JPG

    2_57.rJPG.jpg

    9_57.JPG

    beck 001.jpg

     

    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.

     

     


  12. Well, some of this may have been discussed before, but many questions also remain unanswered.

    1 hour ago, Danube Fiddler said:

     

    Since linseed oil was frequently used in old varnishes, it is probable, that they had good methods for preparation.However I never have read an old recipe without resins - so eventually they didn´t have a sufficient procedure resulting in a pure linseed-varnish without driers or resins. May be they could live and work without it. 

    As I told, I am still wondering, why my sticky-staying oil dries completely not-sticky on wood-surfaces. May be, that the wood provides substances for the total drying ?

    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.


  13. 14 hours ago, Melvin Goldsmith said:

    Strad obviously had access to highly refined oils?

    Really when I look at great old violins or talk to my most highly respected colleagues in the making or restoring fields the search is not for something perfect, solid or modern .. rather it is for fallible ingredients that render a colored but very fragile varnish 

    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.


  14. 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?


  15. On 8/27/2018 at 5:17 PM, joerobson said:

    A note from a varnish geek:

    Linseed oil cooked long enough at the proper temperature gradient when cooled will form a gel dense enough to be cut into cubes.  This was used to polish patent leather shoes. 

    on we go,

    Joe

    Or to catch birds.


  16. 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.