Giovanni Corazzol

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About Giovanni Corazzol

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  • Birthday 02/09/1970

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    giovannisworkshop.blogspot.com
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    gio.coraz.sky

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    Siracusa, Italy

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  1. Hello Palousian, if you expect that the humidity rate is going to be lower in the next months, and if you see that the hair is getting too tight, you can unscrew the frog temporarily and hold it to the bow stick with a rubberband or something like that, and ask the luthier if he/she can gain a little bit of hair length by trimming the head plug, if possible. I learned that the rehair person has to be aware of the weather condition in the area and also where the musician is going to, in order to prevent any problems. I usually leave the head plug as high as possible so that I can take some wood away if necessary, but here in Sicily we have the opposite problem and the hair stretches a lot with the humidity from the sea during the summer, so I try to set the hair just a bit tight, never sloppy or baggy. I know that the hair I normally use (Siberian) stretches during the first weeks. So, I think it depends on the climate in your region for this season.
  2. this is going far from the original question but it is getting interesting anyway! I believe that a good spirit varnish is totally acceptable on a violin even today but, if I chose to buy varnish, I would go for oil varnish. Anyway, it seems wise to me to choose a varnish that will develop a nice, good-looking patina over the years. That's the main reason why I decided to try oil varnish and this was the advice some older makers gave to me. A hard oil varnish looks a nonsense to me and I would fear that it does not age well. I remember discussing this with Gio Batta Morassi years ago, and he had an anecdote about a maker who brought a varnished violin top to a meeting, he showed everyone that the varnish was so tough and he couldn't scratch it, even by rubbing it hard against the bench. This varnish would have obviously turned an instrument sound dead. After some time I started experimenting with Fulton varnishes and I made some terpene resin, but I decided to use natural pine resin instead, and I still have a jar of untreated Fulton resin that is now more than ten years old. But, if I remember well, Fulton wrote that a freshly made resin is necessary in order to prepare the red colors. I wonder if this old terpene resin can be simply heated (with precautions) and turned into a coloring matter for varnish. Would it turn dark brown or greenish brown perhaps? It would be useful if it gave a transparent, warm dark brown.
  3. @JacksonMaberry that's why I recommended a "commercial" (I would say made by a professional) ground... I think that making a good ground can be harder than making a decent varnish... Refractive ground has become much more popular now but, when I was a student I knew about just one company making such a product - it was Northern Renaissance Instruments' Rosin Oil, but it was too complicated for me at the time to buy from abroad (no Internet, no online payments) and anyway, the company discontinued that product after some time because it seems that the process was costly and hazardous. I know just one other way to use colophony in a ground coat (this is from my Cremona school years too): Michelman's varnish (linseed oil+rosinate+turpentine spirits). A maker showed me how to use it as a ground. His method was to mix up enough of the ingredients for two coats, then give a first light coat; on the following day he would take the remainder of the varnish, which was in an already "gelling" form, and use it to fill the pores by rubbing it on the wood. He would finish the instrument with a spirit varnish afterwards. Since the Michelman's varnish can be made using colored rosinates, this is the kind of ground that I would like to experiment next. For now, I am sticking to Gregg Alf's method of mixing up varnish and tripoli powder. What do you think?
  4. ...I just wanted to add a reply to @Davide Sora - and some more about a couple of things @Goran74 mentioned in his post Davide, the instrument that I saw with Alessandro was possibly the viola by Alexander Muradov. But, I remember that we could see a cracked layer under the varnish, there were no wrinkles on its surface. Now, colophony as a sealer was mentioned by Goran, and I hope that Davide will want to add some advice. I have never used colophony alone on wood. Davide Somenzi was our teacher in varnishing class during one school year, and he told us about some ground varnishes that were popular at that time (I think he had attended an Oberlin workshop the previous year) Davide said that colophony and terpene resin must be heat processed if we want to make siccative resins. Heat processed colophony, heat processed amber, or heat processed "Fulton resin" (terpene resin) can give a rich color if used as a ground but, they are likely to cause a stained appearance and even grain reversal. A sealer layer must be used underneath. So, based on what I learned from him, colophony has no use as a sealer -- either it doesn't dry properly or it's too intense and it "burns" the wood. For Goran, I would say that your varnish has a "standard" drying time based on what I know, and also it's important that the varnish has a short "tack-free" time (in Italian this is called "fuori polvere") but also a conveniently long "open time" during which the varnish can be "moved around". adding madder lake or liquid extracts ( like the popular "JOHA" brand if you like them) make the varnish dry faster so please take this into account when testing your varnish. Hope it helps, Goran and please share pictures here on Maestronet when your instrument is finished --Giovanni
  5. Hello Davide, I think I got this information from Primo Pistoni and Alessandro Voltini. They mentioned the use of heated colophony as a varnish ground and said that it was used by many makers in the past. But, we didn't make or use it in Alessandro's workshop. I don't remember exactly which instrument had the feature I was referring to, but it definitely was one of the oldest. Our discussion happened on an occasion I had to see the collection while Alessandro was retouching some of the instruments, as he was in charge of their maintenance at that time.
  6. Hi, Goran74! I am aware that the original Biblioteca Marciana manuscript has a different recipe. In my own one, I just wanted to reduce mastic in favor of the more strongly colored ( by heat processing) colophony. I can tell you about my experience with pine resin varnish. Some important things I learned come from this forum. The information can be found in different threads, but I have no "bookmarks" for them at the moment. (1) I believe that some problems in my first varnish batches were caused by colophony. Simple colophony (turpentine distillation by-product) can be used to make varnish but, I was advised from other makers who make their own, that starting from raw pine resin can give a better result. In any case, I believe that pine resin should be heat processed at a temperature around 250 °C. Temperature should stay under 300 °C to prevent colophony becoming insoluble in oils (this was confirmed by J. M. Lozano in his varnish workshop). The heat processing should give a resin that, once completely cooled does not take fingerprints if you hold a piece in your hand, and it should have a hard, vitreous fracture. I believe that my first batches did not dry well because I didn't pay attention to this. I made the recipe I gave to you in the other thread, in 2012. I still have a jar of it. The pine resin that I used came from Greece; a friend got it at a local company where colophony is processed for the food industry (I believe it is collected as a flavouring substance for wines). We cooked this raw (solid, pale amber) resin at about 250-270°C before using for making varnish. Cooking reduced the resin about 20%. In 2016, I made another batch of oil varnish with a friend from Switzerland. We used another kind of resin, the Strasbourg turpentine (Kremer Pigmente, catalogue #62040). Strasbourg turpentine is collected from silver fir (I must check this one) -- it takes a dark, nice color by heat processing. We had a loss of about 60% on the raw material because Strasbourg turpentine has a high content of balsam oil. First, we let the volatile oils go away at a lower temperature then rised up to about 230 °C. These two varnishes dry well and are more or less the same in resin:oil ratio (around 1:1) For me, both resins are OK and have a nice color. (2) another source of problems for me, was the spirits of turpentine. I was used to thin the varnish by adding about 20% spirits of turpentine to the (cooled down) varnish just after cooking. David Burgess advised me to stop doing that. I will see if I can find that thread. Spirits of turpentine can make the varnish unstable, because it can react with varnish in an unpredictable way. My varnish seemed just OK but, after some time I found it was very hard to brush. I tried to thin it down to a good brushing consistency with different kinds of essential oils, but it didn't work so well. You can give Odorless paint thinner (like the "Sans-Odor" by Winsor & Newton) a try; it can be an easy to find alternative, and it has been tested by some people I know in Cremona. Anyway, if you add spirits of turpentine or another essential oil as a brushing agent, I believe you should use a minimal quantity. If you put too much, the varnish will likely make bubbles in the UV box. Thinned varnish is also less tough and can scratch off. I think that if varnish can be brushed easily, by adding just some drops of thinner (mineral spirits) or no thinner at all, it is just perfect. If it's too thick, you can try to warm it a little (it works well) or, you can make another batch with a different resin:oil ratio. (3) I remember discussing a colophony-based ground with my teachers and some friends in Cremona. It was some years ago... (around 2000-2001) Some makers were used to prepare colophony by heating it to a rather high temperature, to darken it and use it as a ground. My teacher stated that this was a frequent cause of developing a craquelure (of a peculiar, distinctive pattern) in varnish. We saw an instrument from the Triennale collection, with that kind of craquelure pattern. In more recent times, rosin oil (a colophony distillate) was introduced as a refractive ground. You may want to use a modern product for this, and get more detailed instructions directly from the maker. I hope this helps, there is a lot of information on The Pegbox, scattered here and there, it takes some patience to go through different threads and take notes, but I think that it's worth it. Or, better buy a commercial varnish? If I had more commissions, I would seriously think about it... --Giovanni
  7. Hello Anthony, many makers like to use a combination of soap and chalk. a piece of dry, traditional soap (the kind used for hand-washing clothes) is fine, plus a white chalk stick. to make the mixture, start with rubbing soap on the pegs drawing three "lines" along the shaft and alternate with three chalk lines. Set the peg into the pegbox and turn, check if more chalk or more soap is needed. Another method would be starting with rubbing the soap around the shaft and then adding chalk until the grip is perfect.
  8. some threaded inserts have 4 "spikes" and they are called "spider nuts" in Italy. I wanted to make thinner, oval-shaped handles so I cut pieces from a brass plate and threaded, then glued them inside the handles. I made the plates thick enough for the thread to hold and not to wear too soon, the screws are 6mm MA and they are used for mounting the door handles on their shaft. Before rounding and finishing the handle, I place 4 pins around the locking mechanism, and I use 2mm brazing rods for that.
  9. I have saved John Schmidt's address and I will contact him. I have a last question before leaving this thread: what about using HSS steel as knife blanks? I found that they are quite hard to grind properly (I have the CAG brand) but they hold an edge well. I now use a narrow CAG knife for purfling; I have a larger one but it takes too much to sharpen and I need to make a new sliding guide for my bench grinder. I cannot sharpen them freehand without overheating. I recently changed my grinding stone and bought a Norton 38A 60 grit stone, and it's the best I have tried so far. Is there any advantage in HSS over a very good carbon steel? For bowmakers maybe?
  10. Thank you all for your answers. Today I took some time to experiment. I picked up an old "Kogatana" knife blade and tried to reproduce the "Morel bridge knife" pictured above. I started grinding a new bevel by holding the blade square to the wheel, turned the blade and ground the other side (the Kogatana I am speaking about has a central layer of hard steel). The blade got a shape similar to a razor, with a slightly curved edge. I removed the burr and sharpened with my stones, then I returned to the grinder to get a pointed tip and a rounded back. The knife worked fine but, I think it's not necessary to shape the end to a point. I tried to work on an old bridge with the truncated end; then I tried some cuts with the pointed edge. I prefer the former shape. Probably, it's safer for the most sensitive steel. I will see if I can find another knife blank to get more familiar with the process. In the meanwhile, I will check for any other advice, which is plentiful and valuable as always here on Maestronet.
  11. Some makers of artist oil colours like the Old Holland brand have been recommended on this forum because they contain less oil compared to other brands. I have tried the "Italian brown pink lake" which is basically an iron oxide pigment, so it's not very transparent and must be used sparingly. You can also find some different kinds of "colour extracts" made specifically for instrument varnish, these ones can be easier to mix into your varnish.
  12. I found this interesting article some time ago and saved it in my browser's bookmarks; I would like to ask some questions about Morel's knives since I know that there are some people on this forum who were trained in his shop or personally knew him and so I hope they'll be willing to share some knowledge on this. René Morel workshop artefacts - the Cozio carteggio First question is: it seems that Morel was always in search of the best tool steel blanks for his knives. What kind of steel did he use? The article says that the blade stock was made in the Mirecourt style and it had a roughly triangular cross section. All luthier's knives that I can find have a rectangular cross section, so why was this feature abandoned? Maybe it would rise production costs too much? The bridge-cutting knife has another interesting feature that I have never seen before. The blade tip seems to have been ground on the thick side and rounded. I wonder what is the reason to do that. When I learned bridge cutting from Alessandro Voltini at the Cremona school, he advised us to round the side of the blade a bit in order to ease the cutting action of the knife inside the bridge's kidneys and legs. But, we always kept a straight back and a slightly curved edge. So, I thought that the purpose of the grinding was that of reducing the thickness of the blade after it was sharpened, to reach into the thinner spaces of the violin bridge even with a thick knife stock blade. Since I have always trouble in sharpening very fine knife points with a stone, because the points bend a little under pressure, I wonder if the grinding was devised as a solution to this problem. Thank you all for reading and for your comments! --Giovanni
  13. Hello Goran74, I too started my oil varnish experiments with the classic Marciana recipe. At the time, all (reliable) information available to me was Gary Baese's book, that I borrowed from the school library in Cremona. I changed my recipe over the years, but I stayed on a 1:1 resin:oil ratio every time I made a varnish containing linseed oil, mastic and colophony. One change I tried was: 1 part mastic, 2 parts colophony, 3 parts oil. 1- since a deeply colored varnish is desirable, I would use much less mastic and more colophony compared to the original Marciana's. 2- mastic is expensive! So, if I had to choose another recipe, I would take R. Hargrave's version of the classic varnish that he published in his great double bass tutorial. But, the Marciana recipe can work well and I think that Luis Manfio is the expert on this. I have almost always used Strasbourg turpentine to make a deeply colored colophony. Once I used Aleppo pine resin that I collected here in Sicily and it worked fine too. I made another varnish with spruce resin scraped from trees around my hometown, Aosta and I got a light brown-tinted varnish. I remember reading a Strad article by Gregg Alf where he advised using a high resin ratio varnish for his sealer/ground layer, mixed with red tripoli to make a smooth paste that he used to fill the pores before laying the varnish coats. So, maybe you will want to make a second varnish batch with higher resin:oil ratio and use it as a filler in the way that Gregg Alf recommended.
  14. Hello Fiddlecollector, Giovanni Lucchi wrote an article for The Strad about his repair technique and you can find it also in The Strad's "Trade Secrets" Volume II, pages 105-107. You will be able to find pictures of the jigs and milling machine that Giovanni used for the process. I'm not sure that this technique can repair areas much larger than a hairline crack successfully. I would be interested in learning more and help customers who bring in damaged bows. Sometimes they are not aware of the bow's real conditions and it turns out they have paid too much for them.
  15. Hello gtd, I just saw the list of resources you have gathered so far and I strongly recommend to add this book: "The setup and repair of the double bass" by Chuck Traeger (Published by Henry Strobel) important chapters of this book have been added by David Brownell and Will Merchant, especially for crack repair and cleating, adding replacement wood, repairing broken necks etc. It was an useful resource for me besides my own experience in the last 12 years and the tools I designed and made to purpose. I would say that converting this instrument to modern practice is very challenging. Last year I restored an old German bass (much nicer than this one) with the help of my intern student and it took 4 full months. The integral neck was grafted and we made a new upper block, a reinforcement over the back button, plenty of rib repairs, scraped off a lot of old glue of all kinds, unglued and repositioned one of the crossbars, reopened cleaned and glued various cracks on the top, replaced missing parts, full border doubling, new bar, retouchings, new fingerboard soundpost & bridge... I don't know if I would like to do such a job again in my life... But, the instrument definitely plays nicely and the owner (the principal bassist in Malta Philharmonic Orchestra) is happy so there was a reward. This instrument you are working on probably does not deserve all this time and effort, I'm sure you can find a better bass to perfect your skills.