John Harte

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About John Harte

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    West Melton, NZ

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  1. John Harte

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

    At times I've seen it develop in days. Colour (photo yellowing) begins developing and then a washed out appearance starts to emerge. Other pieces of maple and spruce that I have left sitting in the bottom of the cabinet for years have developed a deep golden brown colour with no hint of photo bleaching. I suspect that the spectral irradiance curves of whatever UV bulbs you are using, the number and age of bulbs, the proximity of the bulbs to the wood surface, the wood source, humidity within the box and more may be factors that contribute to whatever you end up achieving.
  2. John Harte

    The importance of varnish

    Possibly not so - At least, according to other researchers... Re effects of varnish, Martin Schleske's article "On the Acoustical Properties of Violin Varnish" may be of interest to some. See here: https://stacks.stanford.edu/file/druid:yx381kq5616/CAS_yx381kq5616.pdf
  3. John Harte

    Development of Taste

    Are you sure that this is the Soil?
  4. John Harte

    Question for makers who work alone

    Here are a couple of shots of another corner from the same instrument. Corners are obviously almost never viewed under a magnifier. It is only under this that gaps, the filler used and bee stings created with a knife cut and filled with varnish etc., become visible. The second shot reveals the more elegant bigger picture aesthetic that you mention which is more towards the reality of how corners are viewed by people like us. I doubt whether Strad would have been too bothered. He seemed to have a good appreciation of the art of the appropriate. (Apologies for stating the obvious...)
  5. John Harte

    Question for makers who work alone

    Julian, is this along the lines of what you might be referring to??? (Attached is a reduced file size of a worn golden period Strad corner.)
  6. John Harte

    Question for makers who work alone

    I make my own purfling.
  7. John Harte

    Don Noon's bench

    Congratulations Don! Well done!!
  8. John Harte

    Any Cremonese Basis for Colored Rosinates?

    An article "The Real Thing" by John Dilworth that appeared in the October 1984 Strad magazine details analyses of several old Italian violin and cello varnish samples carried out by Raymond White. Quoting from this, "White was quite firm in ruling out both Michaelman and Fulton theories in three particular examples. The metal soap rosinates of Michaelman varnish are apparently very distinctive and would have been easily revealed by these analyses."
  9. John Harte

    The ground ( sealing) of the great masters - which was it ?

    I'm not sure that succinic acid presence can be considered a viable marker for amber varnish. Succinic acid has a relatively low boiling point (235°C) which would make it likely that any presence would be eliminated during open pot cooking/running of amber. It seems that the only usable marker for amber presence is Δ 8-isopimaric acid, but there are problems... As Raymond White has pointed out, "Amber has a very low amount of characteristic diterpenoids, the major component of which is Δ 8-isopimaric acid. In favourable cases this might still just show up. However if amber were incorporated with just one tenth of its weight of rosin, the latter's diterpenoids would swamp those of amber." (Raymond White: "Eighteenth Century Instruments Examined", The Strad, August 1984. pp. 256-259.) It seems that there are similar issues with identifying run copal within varnishes.
  10. John Harte

    Extracting a yellow pigment from aloe

    The only study involving Andrea Amati varnish that I know of is this: https://www.researchgate.net/publication/222897899_Microanalysis_of_old_violin_varnishes_by_total-reflection_X-ray_fluorescence An earlier version of this featuring the same element data can be downloaded here: https://www.researchgate.net/publication/297350011_Arsen_und_Blei_im_Geigenlack There are other studies featuring Girolamo and Nicolo Amati varnishes. From what I recall, none (the above included) have identified arsenic in an Amati varnish. This sample size is very small though......
  11. John Harte

    Extracting a yellow pigment from aloe

    David, thank you for this. I was aware of Barlow and Woodhouse and maybe one other study having found arsenic in Strad varnishes but don't recall its mention in recent studies featuring Amati varnishes.
  12. John Harte

    Extracting a yellow pigment from aloe

    If at some stage in the future you again come across this study, I would be interested in knowing what it is.
  13. John Harte

    Extracting a yellow pigment from aloe

    Orpiment is also available from an art material supplier in London but, as Christian mentions, it's too scary. I also don't recall any mention of it having been found in any of the Amati varnishes that have been analysed. Weld (Reseda luteola) produces a useful yellow. ( Extract dyestuff with alkali, e.g., potassium carbonate and precipitate with alum.)
  14. John Harte

    Stradivari's secret was a concept?

    Re alum treatment of wood, some caution may be appropriate. If you google alum treated archaeological wood, some interesting studies come up.