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joerobson

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Everything posted by joerobson

  1. Potassium silicate. There are references in old cabinetmaker"s documents about horsetail as a polishing tool. It was not used flat like sandpaper. The reeds were bundled like a small broom. The ends of the reeds were scored and frayed with a knife. The bundle was the soaked in "weak barber's acid". Then the broom was used to polish bare wood. Barber's acid is a weak lye solution. Silicate from the horsetail + potassium from the lye solution = potassium silicate. on we go Joe
  2. I am always pleased when I am asked to collaborate on an instrument. Ground done . First separator coat applied. on we go, Joe
  3. Sure. The Lady Blunt travels with the original bass bar. The Hill bass bar is in the instrument.
  4. Thank you @John Harte for the excellent photos. And again for your explanation of the inner reflection of the wood fibers. This explanation also goes to the spruce, where we see enhanced cross grain reflectivity..."silking". The ground we are looking at must be subsurface in order to create this phenomenon. Therefore the wetting properties are of equal importance as the reflective characteristics. Surface materials do not give the same depth. The wood has "color" which I see as part of the aging processes, not an applied material. Once the ground is established the translucent varnish....properly applied...creates a lens of variable thickness which is a slight magnifier. I agree with you @Michael Szyper. The ground will dent before it scratches. on we go, Joe
  5. John, Your pictures are always welcome. Joe
  6. I think your observation is correct from a static point of view...as in the hair photo or a poster of an instrument. In real life and varying lights we are looking at light in motion. Especially when observing the spruce.
  7. The issue and relationship of reflection and absorption of light is a complex issue. Perhaps Mike Molnar can continue to enlighten us. From my limited perspective specular reflection is not we observe in well preserved Stradivari ground. Light enters the wood about 7 microns. It is the scattering of the light within the wood and the multi faceted internal reflectivity of the wood that gives the "inner fire" that is remarkable about this ground. In simple terms light is absorbed by dark surfaces and reflected by light colored surfaces. It follows then that the untreated and brighter surfaces would provide a likely source of this phenomenon. Contrast comes from the angle of observation and reflectivity is diminished by the darkening of the wood. on we go, Joe
  8. Linseed oil, pine resins , turpentine The only material I have yet to obtain in sufficient quantity is terebinth.
  9. It is important to remember that the material6have not changed over the centuries.
  10. I think long lower temperature resin cooks to be more likely historically. Just a guess though... on we go, Joe
  11. That will tell the tale.
  12. The harder the resin the less prone to heat degradation. Amber being the hardest one in violin use. As most violin varnishes are made from some form of pine resin/colophony these are the most vulnerable. on we go, Joe
  13. To all the varnish makers out there. This is the time of year that I get lots of calls from players and makers. The subject: case print varnish. To avoid this issue in your work here is a test. On a hot sunny day place a chunk of your resin in an aluminum foil pan in the direct sun. The chunk should have a nice sheer and defined edges. If the sun and temperature melt the resin or even round off the edges of the chunk, your varnish is likely to case print. on we go, Joe
  14. 30 gallon galvanized trash can + 6 18" black light tubes.
  15. Pure larch resin is difficult to find and questionable in origin. The price of this varnish would scare everyone. I do make Balsam Ground Varnish from Venice Turpentine. Larch and Venice Turpentine varnishes tend to be very tough...as in wear and sweat resistant...hence my choice for ground varnish.
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