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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  • Location
    Siracusa, Italy

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  1. @Goran74 as far as I know the only violin varnish that can be made with colophony without heating it, is Michelman's varnish. The problem with colophony, it' s that this resin is too acidic and has too low melting point. converting it into rosinate can be made in two ways. one is by heating colophony with a chemical like quicklime and this was the method used in the beginnings of the modern varnish industry. a better way is to convert colophony to rosinate by dissolving it in an alkaline solution and precipitating it with a salt solution (alum, zinc sulphate etc.). This method allowed industry to produce many kinds of inks for printing. cold-processed rosinates are more pure, more chemically neutral and stable that the equivalent heat-processed ones (temperature around 270 °C is necessary). Joseph Michelman used this process for his varnish recipe (rosinate+linseed oil+turps) and in my opinion this can be a nice ground varnish. When I was in Cremona, I was taught by a Ukrainian maker a clever way to use Michelman's varnish as a ground. mix varnish for two coats and apply the first one lightly. when the first coat will be dry (one or two days) the varnish left in the container will have turned into a gel. use this gel to rub into the wood and fill the pores then let it dry thoroughly. colophony in spirit varnish: as Davide said, colophony is too brittle -- avoid it in s.v. recipes. But you can add a little Venetian Turpentine in spirit varnish. It makes it more tough and improves adherence to wood. I learned this from my teacher, Alessandro Voltini.
  2. Antonio Turco, "Coloritura, Verniciatura e Laccatura del Legno" - Hoepli, Milano Italy 1969 (ISBN 88-203-0947-5) Page 237: Poly-resinous spirit varnishes [for French polishing] [some practical examples are cited] a) Seedlac, 120 grams -- Sandarac, 15 grams -- Manila Copal, 5 grams -- Elemi, 15 grams -- Ethyl. Alcohol, 1 liter this book cites other man-made components that were already common in the trade: nitrocellulose and PVA resins - the latter ones were made soluble and clear by adding 10% ethyl-acetate or benzole. Colophony (heat treated) is also cited as a common ingredient in low-cost products.
  3. I have written a post on my blog also covering my finger planes. For all those who may be interested, here is the link: https://giovannisworkshop.blogspot.com/2020/05/miscellaneous-tools.html I have been using some of my tools for more than 15 years now. It wasn't common for all makers in Cremona to have access to many sources unless we had friends willing to buy and bring home new tools from abroad. Now e-commerce has made a lot of cheap tools readily available, but sometimes the adjustment work that is necessary on cheap tools is not financially acceptable and returning defective items to seller is often impractical and costly.
  4. The finger planes I have made myself are made entirely of brass. I used small sections of a (gas?) pipe and a sole that I connected by brazing with a silver alloy (castolin in Italian). It can be done with minimal equipment but I am aware that not every violin maker likes to do that. Wooden planes are simple to make and they can be basically made in 4 pieces with a bandsaw. After cutting the center section you make the angled cuts for the blade seating and the escapement for the chips and then you glue the two "cheeks" by keeping everything squared and true. You can use pins if you want. I have found a finger plane in another workshop that was made in this way, but size was for cello, too big for violin, and with arched sole and brass cheeks. The center blocks were made in hardwood (ebony or similar). It worked with minimal adjustment. My friend told me that it came from China.
  5. @Nestorvass I see that the opening in front of the blade may be too wide; I believe that if you manage to glue a small plate underneath as Davide suggested, the plane will improve significantly. It is annoying because you will have to find a suitable material (I have used some cut-out from a small company in Cremona where they make brass doorbell plates) then drill and file the new mouth as precisely as you can. A small engineer's file can be very handy for this task. For roughing out, and planing rib stock, etc., making a wooden plane may be an interesting project. You can also make a toothed iron. (I remember a post from Michael Darnton about this) Basically if you make the plane in 4 pieces (2 in the middle + 2 "cheeks") you can place the front piece very precisely and you can do without an added base. I had to add a plate to this one but I don't regret it since it works perfectly now.
  6. Something that worked for me (even for cello) was backing the metal (brass) strip I learned to use at school with some layers of thick fabric (hemp fabric) and putting all together with two wooden handles. I can place my hands on the back of the strip without wearing gloves. The brass I used is 0.4 mm thick for violin and 0.6 mm for cello.
  7. Yes! and, for me the most convenient way to prepare and store chicory is to make an extract, filter it well, add some caramelized sugar and boil it down to a thick syrup. It can be stored indefinitely in a small jar. Putting a few drops of water in the lid and re-dissolving a small quantity of dye (with a brush or a small rag) is fast and easy like having some kind of watercolor. I rarely have instant coffee in the worskhop and nobody seems to like it here anyway! But, apart from that, coffee always turned out to be more opaque than chicory. I don't know why....
  8. Rubbing fine pumice powder with alcohol on a rag makes a very effective sealer for necks. After drying and rubbing hard with a clean linen cloth, the neck becomes really smooth and shiny. A "shoeshine technique" works well. If I need to dye/adjust the color, I do it beforehand. I prefer color "extracts" (Hammerl amber-brown, etc) over artist's colors in tubes, or some oil-soluble "aniline" dyes, and I mix them with a little tung oil or linseed oil. Very little color extract is necessary. This restores the appearance and reflection of the old wood
  9. IMPORTANT: Links to Zoom meetings should not be shared publicly. News have spread about many unpleasant "ZOOM BOMBING" troll activities.
  10. @violins88 I will join the 22.30GMT meeting. I will stay in the kitchen and make some more coffee if I need... This will be an occasion for me to practice my English and I'll be happy to help other participants whenever I can. Looking forward to meeting you all. Thanks, Giovanni
  11. Hi all, I would like to join in your next meeting, but 22.30 GMT is a bit late for me -- I live in a shared apartment for now and I can't stay on the phone without being heard by my flatmate. I am aware that most of the Maestronetters living in the US are spread on several time zones so I understand the difficulty of finding an acceptable time for meetings. . I'll see if there will be any other groups forming.
  12. Hello Lex Luthor, I would have the violin repaired by a luthier and there are a couple of other things that should be checked. Yes, have the tailgut replaced with a standard nylon "Sacconi"; or, you could simply go for a Wittner tailpiece that comes with nylon cord and integrated fine-tuners. the spacing of the strings at the bridge seems too wide from the pictures you posted. It should be around 33 mm from G to E. strings also seem off-center by looking at the fingerboard, and the height of strings at the upper nut looks a bit too high. In general, you could have the luthier rework the violin set-up for better playability. They would probably prefer to make a new bridge and this is right because most of the times reworking a bridge does not make for the best results.
  13. @jezzupeI am not familiar with epoxy glue, so thank you for the detailed explanation of your method!! A friend of mine who makes celtic harps showed me how to use the West System epoxy to make a structural bond in wood. he said that since this kind of epoxy is thinner than other kinds (the common DIY glues I was more familiar to) it can be used to create "glue rods" that are formed when the glue fills the holes that have been drilled into the two parts before gluing. These glue rods become effectively locked into the holes because the epoxy also permeates the surrounding wood. My understanding is that generally, epoxy glues have a high internal cohesion but they do not have adhesion to wood fibers as high as other glues like water-based pva/alipahtic, or hide glue (the last one having the better adhesion, but quite poor cohesion and that's why the hide glue line should be as thin as possible without being "starved"). my thoughts on clamping the pieces (if the OP chooses to go this way): with the machines removed, a piece of wood can be roughy shaped to adapt into the tuning box and long enough to support the scroll. the support can be fastened to the back of the pegbox with a clamp and left in place. It will be placed against the bottom of the pegbox. A wooden wedge covered with cardboard or cork sheet can be fastened to the curved rear side, using some plastic cable clip-holders that go through the machine hole. I believe that this set-up won't take much time for preparation and it makes the gluing with hot hide glue fast enough. Having someone for help in placing the clamps would be better though.
  14. Hello, no matter which glue you will choose, I believe that you will have to make some counterforms to make the clamping force spread more evenly without the pieces sliding. Chuck Traeger covered this kind of repair in his book on bass restoration: "Gluing will not be sufficient to hold the tuning box together" and he suggested using brass screws to make the repair stronger. "I use small brass wood screws, which I insert into pre-drilled holes and countersink the heads as much as possible".
  15. Hello, here is one (unpelasant) thing I learned about wood from Romania https://www.theguardian.com/world/2020/jan/08/violence-escalates-as-romania-cracks-down-on-illegal-timber-trade I have a friend who comes from Romania (Deva) and she says the situation is becoming really awful there. I don't know how tonewood trade can possibly be affected but I would really feel unconfortable in buying wood that was illegally harvested.