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About JohnCockburn

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  • Birthday March 23

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    Sheffield, UK

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  1. JohnCockburn

    UV effect on wood colour when kept in a UV light box

    Longest I've ever done is six weeks. No bleaching.
  2. JohnCockburn

    Ansaldo Poggi authentication

    I thought the thing about these stains being based on the "dirty business" of animals was just an urban myth put about by the mischievous...
  3. JohnCockburn

    Ansaldo Poggi authentication

    Yes, that's what's called "burned flames". It's perfectly possible to stain maple without producing this effect. reverse grain is where the early wood looks darker than the late wood which can happen because of absorption of stain (or coloured varnish on unsealed wood). Again, perfectly possible to stain spruce without producing this effect. Most makers will darken the wood before varnishing. Many will stain, some will use eg UV, ozone or heat treatment, or ammonia fuming, and some will swear by a combination of all or some of the above.. UV is usually involved to some degree.
  4. JohnCockburn

    Ansaldo Poggi authentication

    flames sometimes appear burnt in photos when they actually aren't. I don't think the photos are good enough to say much about the spruce.
  5. JohnCockburn

    Scroll broke off!

    good argument for hollowing out at least the bulk of the pegbox before carving the scroll...
  6. JohnCockburn

    Filtering Boiled Linseed Oil

    I've never found it to be necessary.
  7. JohnCockburn

    Filtering Boiled Linseed Oil

    I just use cloths from old t shirts. Never had a problem getting the oil to go through the cloth. What temperature is the oil?
  8. JohnCockburn

    "I have a dream..."

    Have ye been hitting the NYE sherry a little early?
  9. JohnCockburn

    Boxy, honky nasal sound.

    If you are into violin making for the long haul, sooner or later you'll have to learn how to reset a neck. Why not use this as your learning opportunity? I'd hate to have a 29.5 mm neck projection, don't care what anyone else says. And there must be an issue with the quality of the fit for it to alter so much in the gluing process. Alternatively, a useful "cheat" to raise or lower the projection: loosen the seams on the front everywhere except the top and bottom blocks. Apply closing clamps loosely, adjust projection (you'll find it easy to push/pull the FB up/down in order to achieve this) and find some way to hold the fingerboard at the desired elevation, then tighten clamps. Then reglue front as normal. Merry Christmas!
  10. JohnCockburn

    Del Gesu Kreisler: neck length

    This is just a generic neck template stuck onto the scroll outline. The neck length is meaningless in this case.
  11. JohnCockburn

    Frequency analysis violas

    I had a very interesting discussion along these lines with an old friend of mine the other day, who is a successful and well-respected hi-fi loudspeaker designer. He has found that tweeter choice has a significant effect on perceived bass quality.
  12. JohnCockburn

    Frequency analysis violas

    In this case the "tap" probably has too long a duration for the high frequency results to be meaningful.
  13. JohnCockburn

    ff Hole size

    the thing here is "standard width", which seems to be creeping up...
  14. JohnCockburn

    ff Hole size

    Not as a rule. But an Amati model viola, for instance, looks wrong to me with 7 mm wide f holes. And what happens if you get an old violin in for set up and you think it will benefit from a thicker post than the f hole width? I find this happens on a fairly regular basis.
  15. JohnCockburn

    Soundpost fit and B1+ mode

    little if any effect on frequency. possibly significant(and useful) effect on amplitude.