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Everything posted by HoGo

  1. The line between tradition/ style/ personal touch and plain mistakes is pretty fine. I think every maker sets his own rules for what is "good enough". The methods which the makers use show in the result as you can never realy remove all your toolmarks but only make them less visible - that's the point in succesion of carving steps from gouge - thumbplane - scrapers - sandpaper(optional). You can still see "toolmarks" of sandpaper with a magnifying glass. No one really wants to show his gouge marks or even thumbplane marks on the exposed surfaces visible easily so the scrapers are used to cleanup that which is generally considered good enough bu most traditionally trained makers. For some areas like tight turns of scroll the scrapers would not be easy to use and so most makers just leave it right off the gouge. And that's where personal style shows... some use wider gouge, some less wide, some use finer cuts some deeper etc. Emulating Gesu or Strad work in this area is mostly in usind similar tool and similar strokes and not overdo final cleaning. Emulating some of the rougher workers of the past may include intentional left sawmarks or such. Of course there are makers who do rough mistakes all around the instrument and use marketing talk just to persuade folks it is "the desired style" and sometimes it is hard to distinguish it from the abovementioned "real style". I make mandolins and "sanding to perfection" is the target, and although my hand work has been on the very clean side I can find a few toolmarks here and there - sometimes tiny scratches left by sanding (I use mostly scrapers but do some final hand sanding) or tiny cuts of knife I use to cut binding ledges, unperfect edges of pearl inlay or imperfect fingerboard dots (also handmade) and so on. I could probably do better and not miss some of the details but this is my own general "standard" of good enough. Even old factory instruments can have their toolmarks that give them unique character. There are few vintage Martin D-28 guitars with bandsaw scratches all across one (or both) halves of back. Probably a mistake - shoulda sand/plane away a bit more or the back was thin enough and marks were intended to end inside the box and someone flipped the plate during the process... Or perhaps the marks were not all that visible on new instrument and called good enough and now they show much more after decades aof aging and give that guitar a special look...
  2. I always wondered what ground they used for old church seats. The worn spots where all the folks put their hands when entering or leaving the row look just like the old well worn spots on cremonese violins... Even not so old wooden handrails along stairs or older wooden gym benches often have this look. Bare oxidized wood, darkened and polished and sealed by sweat/ dirt and whatever people have on their hands. Often the top layer feels like a hard wax or old french polish... Sweat contains lots of stuff...
  3. OMG, wait till water is banned as you can drown in it...
  4. I believe California did just the opposite and banned the clean ethanol (everclear). Denatured (with methanol and another s**t added) is not banned there...
  5. Probably because when tonewood dealer finds a knot in cello sized maple they cut it down into clear violin/ viola wood and sell it for better profit than downgraded cello wood. Poplar or willow is not so famous for smaller instruments so they are not as picky...
  6. Nice video, but I agree with Don, the terminology should be clear before myth-breaking. I laways thought of glue joint strength as relative to single piece of wood with the same grain orientation. That would give you strength of end grain joint somewhere near 15-20% of single piece while side grain joint would score 100+% easily when compared to single piece with the same orientation. The result of side-to-end grain joint is clear where the glue holds well on the wood surface and the side grain piece splits before the glue adhesion fails. Adhesion strength of modern glues is undisputable, creep over range of temperatures or humidity changes not so much. If I were to connect sticks end to end I would choose finger joint over butt joint.
  7. Agree with you. I think the problem of objective evaluating violins is just natural thing and even the best players or makers will evaluate the same violin differently. Same as competition judging. But it is not important to have "objective" exact rules. Every maker evaluates his own instruments with his own ears and help of a good test player or two. The same would work for this purpose. Give each instrument mark for tone color, carrying power, clarity, etc, whatever you consider important and don't look into spectrum or modes as you're looking into black box no one can decode right now.
  8. Here in EU I used to buy denatured alcohol at pharmacy. Denatured ethanol with some additive (I read "gasoline" in MSDS which can be many things), no methanol as it is used for disinfection. It's scientific latin name is "Spiritus cum benzino denaturatus" and comes in 96% ethanol. Ten years ago I started having problems getting it without prescription from doc. They also sell "spiritus dilutus" whih is probably the same diluted to 60%. I tried to by HW store denatured and if you read the MSDS of each brand (here it is compulsory to list ingredients on the sticker) you'll find the ingredients and percentage vary wildly (though no methanol here). I got some pure undenatured pharmacy grade ethanol as well but it is expensive as heck but finally settled upon "bioethanol" sold as fuel for ventless fireplaces. It is largely supported as ecological fuel in EU a I can get it in 99.9% ethanol with trace of bitrex (denatonium benzoate) for 2-3 EUro per liter - best stuff ever for shellac. Does not smell bad or contain other toxic substances like methanol, just tastes bitter (VERY bitter) Similar stuff is sold in US and some companies will ship it... I think I read the ventless fireplaces are banned in CA so you'll have to search a bit but it is supposed to burn well witout soot or other bad things.
  9. I don't think you need to measure the performance quantitatively - If you could do that you would be half way down to discovering how the darned thing works without any AI. Good old statistics and few good players could pretty much grade the violins into 5 or 10 qualitative categories and use that. Much like AI in OCR, the input images are mapped onto a set of characters...
  10. That was discussed here some time ago I believe. While I strongly believe AI and similar modern approaches have something to say here, the violin business is not the area where use of these technologies will generate enough extra profit so implementation will not be worth the investment unless some scientific grant covers it. I wrote it few times in old threads that these technologies have already been used in similar areas for many years. I still remember my first encounter with this at a math conference some 15 years ago where professor of applied math/ IT spoke about their research for a private concern where thay applied these tecnologies / theories (black box analysis, fuzzy sets, NN, AI) to replace human control of production processes with success. The whole thing was based upon learning from real people in real environment. The main application involved pulp/ paper making where tha main problem was just like in violin making variability of raw materials which is mostly wood. The experienced workers learn over time how to adjust the processes of the line to get best end results and the research managed to use AI to replace most of them very reliably using arrays of sensors. AI can easily learn from such live environment if you can provide measurements of sensors and good quality feedback. There are commercial AI packages that can replace human working at computer (like accountant or such) by "looking over his shoulder" for some time learning what he does with documents... I can see someone like Yamaha apply this to their production. With good measurements of all possible variables and good feedback it is nowhere near impossible (this would require judging of quality of instruments that is quite subjective but with experienced player at the QC still doable) I don't see much use in workshop of single makers with limited output, their old school brains can usually do good job. I think the Gonzales et al. paper shows quite different approach as it is completely removed from reality and they are trying to emulate theoretical model (FEM etc...) with AI.
  11. Most common and by far largest european maple is acer pseudoplatanus and that's the stuff most folks use for violins and bridges - bosnian maple is just this exported from Bosnia (if you trust your seller). The acer platanoides (so called norway maple) is another species of maple rarer and rarely cut for violin wood. Third common species here is acer campestre (we call it field maple but I've seen hedge maple used by english speakers) is the "oppio" Strad sometimes used.
  12. Doesn't this approach change static loading of the structure? The longer lever acts especially towards the top edge. How much does this affect the tone?
  13. That's interesting. I wonder how qualified audience in concert halls is. There are so many contradictions in violin trade... I read/hear so often how an artist had to work really hard to learn to play a Strad (or other valuable name) but it was worth it because now he projects into the large auditioriums and listeners can enjoy the music. Also often said that strads don't sound good under ear (to player) but good for audience. There is much more psychlogy than hard physics in evaluating violins...
  14. Too late. Don't you know the biggest factory in Luby (former Schonbach) in Czech republic was called "Cremona" Luby. They churned thousands or even millions of cheap fiddles a year from 50's till 90's...
  15. The old texts mention spirits of wine that has been rectified(distilled) at least four times... that can get you above 90%. I buy anhydrous ethanol dirt cheap, like 3 Euro per liter. Sold as fuel (bioethanol) denatured only by traces of bitrex. I consulted with the producer and it is above 99.9% ethanol (in the final denatured product). Best stuff ever for dissolving shellac for french polish. I've got a bottle of pharmacy grade ethanol and that is 96%.
  16. In my experiments I followed information I collected from various papers. Basicly I baked for an hour or so at 100+C to get rid of most water then immediately packed the wood into thick aluminum foil with as little air trapped as possible (of course there is some air/oxygen in te wood but it didn't affect the results - the goal is not to burn the wood) I packed it well and sealed with aluminum tape (heat resistant). Then I baked it at 160-170C for few hours (first samples for 4 hours, the real wood for a few more) and let it cool slowly for a day or so. Then opened the packing and let the wood sit for few days. I weighed the wood to find out when it reaches equilibrium. Without the aluminum foil the wood would burn or at least darken to dark brown color. There was no problem with steam coming from wood so no need for vacuum. But this is different from "wet" process as te water surely causes some hydrolysis and other changes in wood that the dry process does not.
  17. I don't know about violin players but there are more than just a few top level mandolin players who are lefty and play righty. Chris Thile being one of them.
  18. CT is reliable but problem usually is somewhere between the screen and seat. There are various CT scaners, the modern micro CT are extremely precise (but expensive), the old common CT's are nowhere near that, something like 0.5 to 1 mm voxel size. You can approximate a lot even from such fuzzy data but the operator must know what he is doing.
  19. Are you using some professional pressure cooker? 170C steam is at about 9 BAR pressure, that is not that much, many common pressure chambers for steam bending wood can handle that. Of course DIY units made of PVC pipes or such can explode and cook someone alive. I've done some "baking" of wood but without steam in oxygen free environment. I did measure density only.
  20. CT scan is fuzzy voxelized object and the density is calculated by the sw for each voxel (color darkness is proportionate to density but the machine must be well calibrated with samples of known density) the edge voxels may be half air - half wood and their calculated density will be distorted. If those voxels are included in the final calculation, the average will be too low.
  21. Doesn't potash and alum generally desctribe the same thing? Potassium aluminium sulfate?
  22. I just can't see any bending problems with violin ribs that are 1mm thick. I bend mandolin curly maple ribs at 2mm+ thickness and some of the bends are just as severe as violin c bouts. Takes helluva patience to bend smoothly. One problem may be with maple that has "runout". Runout combined with heavy curl will make some parts really splitty. I would recomment using sanding belt as backing strap for those and bend slow and almost dry, it keeps the outer parts of end with less tension than using steel strap.
  23. No, it comes with free internet expert opinon :-)
  24. Big Brother (Google) watches you and wants to know who browses their web :-) That should be safe, but I personally never follow these links.
  25. If you use clamps you can plane dead flat. But tiny gap in the center can help keeping the ends closed when center clamp is tightened first and the end clamps added after that. I experimented with clamping order and even when the dry wood mated perfectly when dry clamped on one end only, after rubbing the joint with glue and end clamp added the other end opened visibly presumably because the added moisture. So I prefer application of two clamps simultaneously on both ends and then add third in the center. If you intend to use rubbed joint with no clamps you'd better plane some hollow into the joint.
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