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Giovanni Corazzol

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About Giovanni Corazzol

  • Birthday 02/09/1970

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  • Website URL
    giovannisworkshop.blogspot.com
  • Skype
    gio.coraz.sky

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  • Gender
    Male
  • Location
    Atelier Tranin, Lyon, France
  • Interests
    audio electronics and acoustics
    vintage audio effects
    guitar, piano and double bass
    classical, alternative, jazz, progressive rock music
    foreign languages

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  1. Dear fellow makers, I have been living and working in France for three months now. During this time I have started to do a thorough cleaning and inventory of some areas of the workshop. A large cupboard containing many bottles of old varnishes and chemical products has given me some concerns. I have found some products that are well known in the trade, like Potassium dichromate, K2Cr2O7 this was obviously used as a chemical dye - probably for necks. I wonder if some safer replacement exists. Unfortunately, some folders containing notes by the previous owner have disappeared and we are left with no clues about some chemicals that were stored in the cupboard: - Ammonium chloride, NH4Cl - Potassium chlorate, KClO3 OK they are oxidizers too, but after looking up on Wikipedia, potassium chlorate is something that I would prefer to dispose of properly unless it is really useful. it was stored near to a bottle of sulphuric acid, perfect for making fireworks. We would rather go on making violins as usual ;-) Any comments and further information about the chemicals above is very appreciated! Giovanni
  2. who's the maker of this product? Do they provide application instructions? as my experience with Super Nikco suggests me, this product actually cleans and degreases the varnish surface very efficiently but I don't believe it leaves a protecting coat over it. If this product has been formulated after the traditional popote of the French ébénistes, and based on the safety documentation, it may be just a mixture of distilled water, alcohol (ethyl- and isopropyl-), mineral oil, glycerol, powdered abrasive. The methyl-ethyl ketone may be just coming from the denaturing of commercial ethyl alcohol to make it undrinkable. Some insight on the chemical composition of varnish polishing compounds can be found in Antonio Turco's well-known (in Italy) "Coloritura Verniciatura e Laccatura del Legno" published by Hoepli. Some recipes for making emulsified wax polishes are provided. I don't have this manual at hand now, all my equipment is still in Italy. If anyone is interested I will post a translation as soon as possible. Wax on violin varnish: I use Renaissance Wax as by Christian Bayon's advice. I also use a commercial violin polish made by Hammerl. This is definitely waxy and I find it great for old, scratched and opacized varnish on old factory instruments.
  3. Don, it's a very good remark you made here. I don't have my notes from my Cremona school years at hand, but I remember some articles from the Catgut Acoustical Society written in the 90s. The main vibrating frequencies from the violin corpus, neck, fingerboard and tailpiece were listed, and the modes were illustrated and placed over a piano keyboard for reference. I don't remember the process that was described in the papers, but it probably was making a set of tailpieces available in different weights and lengths, plus some plasticine and small weights (I have found small metal printing types, birdshots etc.) to change the weight a little. But, the tailpiece fastener also matters. Changing the tailpiece fastener length and elasticity makes the resonating frequency move too. Carleen Hutchins wrote that tailpiece tuning was a useful practice in adjusting the response of some violins. She provided anecdotal evidence in the paper but not much about the methods for measuring the vibrating frequency. Maybe she did so in other papers.
  4. you will be able to find one as part of a template set - for example: https://www.dictum.com/en/measuring-inspection-instruments-jbo/herdim-outline-templates-5-piece-set-violin-guarneri-kreisler-1733-739403 or https://www.grandiliutai.com/negozio/molds/violin-internal-mold-kit-messiah/
  5. Moving to Lyon, France in two weeks!

  6. Hello Mr Koo! in my experience, basses are like big cats. I don't know if you have pets, but you see, dogs want the toy, cats want the box. I have never seen such a wedge on flatbacks - I wouldn't place a wedge-shaped shim under the post because, even if the fit would be better in one particular point, I expect that there would be a great difference in tension when the soundpost is adusted. It seems to me that basses "like" a looser fit (I mean, the post has to be fitted well but it should allow wider movements). A light chamfer on the top of the post is very useful. We have a relatively stable (humid) climate here but when I visited a shop in NYC (D. Gage) I saw how many basses were in for adjustments and crack repairs everyday! (it was during the winter). I hope that other experienced makers/repairers will join this discussion. For me, Chuck Traeger's book was a valuable source of information and I believe it's a book worth reading even for makers who work on basses only occasionally.
  7. Could it be that your customer installed a fine tuner for the A string and the tuner is cutting into the string? I know about the defective Dominant strings but I remember it was years ago. I had a problem with another brand recently. Some Warchal violin strings (Ametyst?) had a tendency to break, and when I met Mr. Warchal at Mondomusica I asked him. He said that he was aware of the problem and that they had just modified the shape of the ball ending because they noticed that when the string was installed with the "trench" in the ball misaligned to the direction of the string, the string could break suddenly. He advised me to check this when installing strings, especially with fine tuners.
  8. with the P&H Carbon bow, you are planning to use their prepared bow hair hanks, what if you are not satisfied with the quality of the hair they supply? It may be worth trying though, since it's a bow that you can easily re-sell if you don't like it. I have a customer who is a professional orchestra player and touring musician. He bought a series of carbon fibre bows (the Carbondix, which is a popular brand here) , he chose the best two for use in touring and recording studio (yes!) and sold the other ones.
  9. Hello Mr. Preuss. I think I have a similar problem here in Syracuse, Sicily. I have experimented with using a different solvent for shellac-based retouching varnish. Ethyl lactate seems promising. It is sold in Italy as a xylene substitute in cleaning operations but I found that it acts differently from xylene. For example, it's not practical to treat and remove hardened rosin spots on old varnishes with ethyl lactate. But, when mixing pigments and applying retouching varnish, I think that ethyl lactate works well in humid environments. For me, adding a few drops of ethyl lactate to pigments/varnish looks like using spike oil for brushability but it hardens much faster. I will try to make an isopropyl alcohol/ethyl lactate mix for a simple retouching varnish (shellac + sandarac). The idea is that ethyl lactate would compensate for a faster evaporation and allow a better brushability. It's a pity that ethyl lactate has such a bad smell compared to spike oil. I'll be happy to hear about your results if you decide to do some experments with those solvents.
  10. @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.
  11. 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.
  12. 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.
  13. 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.
  14. @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.
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