Davide Sora

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About Davide Sora

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  • Birthday 01/07/1964

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    https://davidesora.altervista.org/

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  • Gender
    Male
  • Location
    Cremona, Italy
  • Interests
    Violin making

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  1. I don't know, it's not on Rivolta's wood that I bought, The brand look Chinese, but maybe it was put after the purchase or for some other reason, who knows. Just at dinner, it's early for the bed..... I think I have to thank genetics, but also an insane love for rock climbing since childhood, which continues on an ongoing basis today (well, in recent years the climbing activity has dropped a little but not exhausted). Perhaps the real secret is that I live in a house on three floors without a lift (the workshop on the ground floor), lots of stairs.
  2. Not much UV tanning on the inside, maybe a few dozen hours, but the maple was quite old (1988) and this helps a lot with color . The willow has a really beautiful color that match very well with maple, I confess it's one of the reasons that pushed me to use it.... Casein is also already applied, which darkens the color a little and increases its saturation, the instrument is a viola I made in 2015, just before closing the box.
  3. Damn, you caught me, better to put on the top to hide the inaccuracy... But yes, let's say for expansion, in fact it is important not to force the lining in the mortise, better to risk leaving a slight gap rather than forcing them in. If the gap is too wide (remote risk of buzz from glue fragments), you can always insert an additional willow strip. I cut the width of the mortise by eye and when I guess correctly, the gaps closes with the swelling of the wood caused by the glue without becoming forced. That's the theory behind.
  4. Yep, I meant just that, it wouldn't be a good idea to use low-density wood and then fill it with glue, but taking the right precautions you described works fine. Also willow can be very low density and behave like a real sponge and the same precautions must be taken as well.
  5. Too kind, but I must warn you that this is not a feature of Stradivari's linings, he rounded them up against the block. Instead I think that a little extra gluing surface doesn't hurt in this area. I bought the willow a "few" years ago from Rivolta, in Mondomusica, he still sells it but surely not the same tree...... https://www.riwoods.com/list.aspx?s=1&ss=1&c=5 I bought the 450x110x45 pieces, do not have an extremely low density like Don's spruce but it is still quite light (0.38/0.40 range) and it cuts more easily than spruce. Ideal for top and bottom blocks that need some strength, for corner blocks Don's solution may be a good idea to save weigth, but such a low density (0.29 is really low) gives me some concern about the excessive absorption during gluing and glue sizing, that would absorb a lot of glue.
  6. I believe that making them concave would lighten them, making them convex take away less wood. Although I don't think it makes a big difference in weight, so I would give it a more stylistic value. But I never tried to calculate the difference, did you do it out of curiosity?
  7. Interesting convex shape of corner blocks, is there any particular reason why it is not concave as usual?
  8. No ammonia because the casein is already dissolved (by borax) and ready to use, it is a base for casein paints, not a specific product for violin making. I used it for a while, but now it has become really too dense and I probably should buy it back. But I don't like waste, sooner or later I'll try to make it with the borax powder I bought. At the moment I use my Ammonium/Calcium recipe because I can make it fresh for every violin, ammonia do not leave traces (I suppose) and calcium hydroxide leave some calcium trace that are often found on Stradivari too and it is also the basis of casein glue historically used by woodworkers. The main difference I noticed is that with my recipe it becomes more brittle and that of the bottle is more flexible and less hard, but I cannot understand if this difference is due to the different alkalis or to plasticizers perhaps added to the industrial product. To dissolve casein you need an alkali, it can be ammonia, borax, calcium hydroxide or others but only one of these is enough to make it work.
  9. Yes, no expiration date on the bottle, but after about a year there is a bit of yellowing and the viscosity increases, although it doesn't seem to change much. Anyway best to keep it in the fridge, a bottle should last for many hundreds of violins No recipe needed, it should only be diluted with water and is ready for use, I used it at 4% concentration as in my recipe but to calculate it I had to know how much water was already present in the bottle, so I put a small quantity on a glass and let it dry thoroughly, weighing it before and after the drying then making the subtraction. It's easy and I think you should do it to understand well what your bottle contains (there is not even the date of production and it could be old and more viscous, who knows). Make tests on a plastic sheet to see if it dries well and to assess hardness and flexibility, and on the glass to assess transparency. I found a water content of 20%, so to get to 4% concentration I added distilled water in a 1: 4 ratio ( 6 g casein from the bottles + 24 g of distilled water, stir well and use). You can also make it yourself with borax (Kremer sells it) and casein, I remember that someone on this forum had posted some recipes to make it some time ago. I bought borax last year at Mondomusica, but haven't tried it yet Protection against bugs is interesting.
  10. I have also tried this casein borax and works fine (diluted, not as is): https://shop.kremerpigments.com/en/mediums-binders-und-glues/water-soluble-binders/mediums-und-natural-gums/5727/schmincke-casein-binder It is a little more elastic and this makes me think about the use of some plasticizer and the bottle is big (half a liter and is concentrated) so you will waste a lot when it has become too old.
  11. What about this? I think it's an excellent idea and makes us understand the importance of the perfect adherence of the strap to the ribs during bending to apply forces as evenly as possible , given that no heat at all is used here . I don't have this gadget, but I know the violin maker who made it and says it works great, he has one for cello too.
  12. Don't worry, I didn't take it as a criticism towards me but as a useful confirmation of what I thought too. I had also read somewhere that even UVC lamps produce ozone only if the glass is of high purity, otherwise it is not produced. But I don't feel able to affirm it with certainity and in any case I think it's better to stay away from UVCs.
  13. Is what I believe too, but I cannot support this by disproving someone who is supposed to have studied it enough to affirm so in a published article, a problem that often arises talking about scientific topics related to violin making. For this reason I decided to just report the extract from Padding's article without commenting.
  14. I don't think so, there are often traces of burns on the C and corners curves in the classical instruments that would seem to testify the use of a hot iron. Not scorching the C ribs using a bending iron heated on the stove is rather difficult (personally experienced).
  15. Just UV tanning, about ten cycles in the UV box over a couple of weeks for a total of about 200 hours of exposure. Ammonia is needed to dissolve casein (ammonium caseinate), the amount of calcium hydroxide I use would be insufficient to dissolve it. I think this makes it an ammonium and calcium caseinate. Real casein glue is only calcium caseinate, but to make it you need to use lime (calcium hydroxide) and not just lime water and in a much higher quantity. I prefer ammonia because I have the impression that a high amount of calcium hydroxide makes it too hard and chemically reactive and even more brittle. If you like you can add a few drops of linseed oil making an emulsion to give it more elasticity, but I prefer not to do so because I like the stiffening effect. I also apply it on the inside of the box.