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John Harte

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  1. Almost certainly whalebone, and possibly just black whalebone. Others will hopefully reply who know more.
  2. Phosphorous is present in both plant and insect red dyestuff material. Table 1 in The Strad article lists pigments and dyes being involved in a number of the considered varnishes. (Oddly this information does not appear in the related Table 2 in the paper version.) The Strad article also seems to include a somewhat more detailed description of exactly where the microsample material was extracted within varnish layers, their stated intention being to "extract and analyse varnish mini-fragments of no more than 20–30μm³, in order to avoid measuring the impregnated wood strata or external contamination". In other words, this study is not about the ground but the original upper stratum forming (coloured) varnish layer. Given this, it would be interesting to hear more about the form in which pigments and dyes might be present and their specific make up.
  3. I would think that it was on purpose. It's an easy way to make a bee sting look longer and/or create a better match between all four corners. Bee stings formed by the purfling itself can and usually do vary so a knife cut can be a quick way of making things look a little more even. Below are three corners of a 1721 Strad.
  4. Hi Dave, Nice to see you back here posting again! Cheers, John
  5. Around ten years ago I tried sourcing Norway spruce resin and the only material that I could find that was reliably Norway spruce resin was a form of chewing gum sold by a Swedish company. I contacted the company and received a very detailed explanation of how and from where the resin was collected and how it was processed. I bought some and cooked it as per any other pinaceae resin that I had previously cooked. From memory, it seemed to liquefy satisfactorily but when combined with heated linseed oil, everything turned to snot. Addition of solvents at a lower temperature did nothing in terms of breaking down or increasing the mobility of the snot. Several variations were tried but all produced the same result. I went back to the company and via further discussion, discovered that this chewing gum was actually callus resin. (Callus resin is apparently more palatable whereas oleoresin has a bitter taste.) I subsequently managed to get the resin collectors who worked for the Swedish company to collect a small amount of spruce oleoresin for me. I also managed to collect some myself from a stand of Norway spruce trees in a forest several hours drive away from where I live. Both of these resins produced good workable varnishes. A good paper that explains differences between callus and oleoresin is: https://www.degruyter.com/document/doi/10.1515/HF.2008.070/html Below is Figure 2 from this paper. Of interest is the lack of resin acids in Picea abies callus resin. I suspect that this may be behind callus resin not working versus oleoresin working.... Possibly related, I have often wondered what the specific effect of adding quicklime to something like a pine resin during the cooking process is. Reducing resin acid content is usually mentioned. If my suspicion is correct regarding the lack of resin acids and callus resin not working, why does lime treated pine resin still work? (I have made varnishes where quicklime has been added to both the resin and oil components and these have worked seemingly without issue.) Apologies for the long winded reply..
  6. Only if it includes callus resin. I am referring here to Norway spruce.
  7. It is relatively easy to make a workable varnish using spruce oleoresin that behaves in much the same way as a pine resin varnish. Spruce callus resin should be avoided though.
  8. Yes some form of stain could well be involved. At least some wetting of the wood structure with varnish or similar seems important in achieving the type of look seen in my photos. Other factors like wood ageing etc., etc., also seem to make a difference.
  9. Joe (and Mike) I was hoping you wouldn't see my post... Five reduced size photos are posted below. Each is labelled, indicating instruments involved and the direction of the point source incident light. The first four photos feature spruce while the fifth, maple. Maple is a more complex situation due to the undulating nature of the fiber direction. Of note in the first two photos is incident light focused along the grain resulting in the medullary rays/plates at right angles to the incident light strongly reflecting light. In a relative sense, most of the other wood cell structural detail seems absent. In contrast to this, the next two photos illustrate the effect of light focused across the grain. Here the along grain structural detail reflects light while the medullary darken/appear absent. If spruce viewed under a point light source is rolled relative to the light source, it is possible to see the various medullary effects at different levels move relative to one another, creating a sense depth. In maple, not only do the medullary appear to move relative to one another, but the undulating fiber direction and how it reflects light or not creates the light and dark areas that we see as flaming. The final photo below featuring a section of maple hopefully suggests this. I hope that this all makes sense and does illustrate that it is components of wood cell structure aligned towards or at right angles to incident light that reflect light. I may be able to find some photos to illustrate the extent to which light can penetrate wood structure, but that will take a little longer than this.
  10. Light enters far further than 7 microns. Based on my own observations I suspect up to 6 cell layers deep. Each cell is approximately 30 microns wide so that's quite some distance. I agree with your second sentence quoted above. Interestingly it seems that it is the components of wood cell structure aligned towards or at right angles to incident light that reflect light. I can possibly post photos to illustrate this if you are interested.
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