John Harte

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About John Harte

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  1. Secrets in the wood (Stradivari's maple)

    Thank you Don. This is very interesting.
  2. Secrets in the wood (Stradivari's maple)

    I agree regarding time effects. We don't know. I should also mention that my comment relates to spruce only. (From my notes it seems that I did treat some maple but would have to find that...) Re spruce, I wouldn't describe my result as a modest grey. It was somewhat more pronounced. There are several respects in which this wood changed as a consequence of treatment and appears to differ from what I have generally seen in Strad belly wood. Your results and experience could well be different from mine; i.e., different wood, different concentration and length of treatment, different viewing conditions etc.. And then there is the question of what we are each actually noticing. It would be interesting to know what different growing conditions can contribute. In terms of treating wood, it would be interesting to know the extent of soaking in borax required to lift levels to 20-60ppm from 5ppm. It may be considerably less than what thorough long term soaking might produce. It could also be that a relatively homogeneous soaking may not reflect the reality of Bruce's sample material. (I suspect that his data represents an overall reading for a particular weight of sample material and will not reflect any variation that might exist within that material as could result from surface treatment versus thorough soaking. It would be interesting to hear comment from Bruce on this.)
  3. Secrets in the wood (Stradivari's maple)

    Bruce, perhaps I should have been more direct in what I was trying to convey in my earlier post... I have seen what I think is varnish penetrate through a maple back. My best guess is that the upper bout region would have been at least 2mm thick. (If this is the case, then my next best guess would be that a stain or thin free flowing treatment might have the potential to penetrate even further.) Re material from soundpost patch beds, this could have come from an area very close to the outer surface, or even virtually at the outer surface; i.e., next to the varnished outer surface. I agree with your interpretation of Brandmair's photos. However there could well be significantly greater depth staining effects if exposed surface end grain was involved. It is good to hear that you now are able to measure for Cl, Si and S. As I have mentioned, these elements feature in other studies involving Strad maple. Have you tried thoroughly soaking spruce or maple in a borax solution? In my experience long term thorough soaking in a borax solution seems to change appearance in a way contrary to what I have seen in Strads.
  4. Secrets in the wood (Stradivari's maple)

    I hope that you will be able to include data on Cl, S and Si presence. These elements feature in other studies involving Strad maple.
  5. Secrets in the wood (Stradivari's maple)

    I am not so sure about this. I have seen what I think was probably varnish sitting in large vessels/pores on the inside surface of the upper bout of an old Italian violin back. It should be noted that the Amati maple and spruce sample material that you have received from me came from soundpost patch beds. Some of this material could have come from an area very close to the outer surface. It would not surprise me if some of your other sample material came from similar, especially if it is in the form of gouge shavings. One of the interesting findings in Brandmair and Greiner's book “Stradivari Varnish” is the identification of a wood stain as distinct from varnish within the upper wood cell structure. If(???) this stain was applied to the bare wood prior to any varnish or size, it could well penetrate to a considerable depth via maple large vessels/pores (as opposed to what might happen via the much smaller tracheids). If the material you extracted from the neck came from an area where end grain featured, a stain presence could conceivably be involved. Not so long ago I tried a quick and dirty experiment applying black stain to some maple end grain. Within a minute or two, I cut into the maple to see how far it had penetrated - If I recall correctly, 37mm.
  6. Secrets in the wood (Stradivari's maple)

    By minerals are you referring to particulates? If so, that may relate more to ground material. As in Bruce's study, Brandmair did find trace elements within the wood structure.
  7. Secrets in the wood (Stradivari's maple)

    I wonder whether it is still too early to develop strong views on the reasons behind the unusual elemental composition that you have found. Targeted wood treatments may have been involved. However there are possibly other potential explanations that should be eliminated before accepting this as the most likely scenario. Could it be that the unusual elemental composition had something to do with creating a certain visual result as opposed to it being a wood preservative or deliberate acoustic enhancing strategy? What does your co-author Brigitte Brandmair think?
  8. I see the inclination of the purfling broadly following the curve at the point that it is set into it. (This is not well expressed but I hope that you will understand what I am trying to say.) There are better images that you might like to consider. The CT scan axial slices shown in this book are an example: http://www.cremonabooks.com/eng/shop_dettaglio.php?id=3103
  9. Yes I agree. I have noticed this feature in a number of CT scans of Cremonese instruments.
  10. Cooking linseed oil (pic)

    Several years ago I had a major problem with cooked in colour washing out of oil varnishes during drying under UV. I had changed from using a particular artists linseed oil to Kremer's Swedish cold pressed linseed oil. Washing the oil seemed to solve this problem. Your comment regarding high-acid resin behaviour is interesting, as are previous comments in other threads on neutralising resin acids. Have you ever experienced problems combining resins treated with CaO with linseed oil? The reason I ask is that I have had no luck making varnishes using Norway spruce callus resin which appears to have very low resin acid content (See: https://www.researchgate.net/publication/249925573_Composition_of_callus_resin_of_Norway_spruce_Scots_pine_European_larch_and_Douglas_fir ) On the other hand, Norway spruce oleoresin works without issue.
  11. Kremer's new violin ground

    What you see in this photo is most likely both - A little original and some polish. This is my impression based on what I saw at the time that I took the photo.
  12. Kremer's new violin ground

    I'm not sure whether Fred is referring to late growth lines or medullary structure. The attached closeups taken under magnification show both but were taken under certain lighting conditions that don't apply under normal viewing conditions. The larger view cropped photo is more towards what you generally see under normal conditions. The medullary in this photo can be seen as light mottling. Instruments vary and lighting plays a huge part in what you see, or not. And, unfortunately, photos never fully capture reality...
  13. Kremer's new violin ground

    Thank you FiddleDoug and Violadamore for your interesting comments. The appearance and shelf life of at least 12 months fits better with what you mention as opposed to something involving casein glue.
  14. Kremer's new violin ground

    It is interesting that Kremer's new product is listed under mediums, binders and glues. The description mentions a hardening component and, from appearances, it looks to be more than just calcium hydroxide.. Could something like casein be involved? Further to Mike C's comment - Barlow and Woodhouse's SEM photos of their Strad samples show particulate layers on/above the wood surface that are in the region of 40 - 60 microns thick. This is far thicker than what other researchers (e.g., Echard and Brandmair) have noted for identified initial coatings on Strads.
  15. Bruce, do you have access to any analytical technique that might be able to identify the presence or not of Si, Cl and S? These elements appear in the wood structure of other studies involving analyses of Cremonese varnish sample material.