FredN

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  1. Beady eyes... extreme version of fisheye

    Hi Don, just my opinion, adding a solvent to spread that stuff will ultimately give you a crackle finish when it leaves the mix. It looks like there is total surface tension and no surface adhesion, like water on a duck's back. fred
  2. Hi Michael- another problem for someone to tackle, for if you apply an umber varnish over reflective yellow it will trend to a red. I've tried Burnt Sienna that has no manganese, only iron, aluminates and silicates which give a transparent red, but not very strong. I do very little of anything, the old age infirmities have arrived. Hope all is well at your end. fred
  3. It is a common procedure when making an oil/resin varnish to apply heat to accelerate bonds in the oil to re-form to accept oxygen, interact oil and resin, and to shorten the time for the varnish to be tack free. While heating the mixture, a dab is usually dropped on glass, then touching it with a finger to pull a string of varnish which indicates state of the cook. Instead of this string method I've often advocated using surface foam as an indicator, heating high enough to build a stable foam, and when it sinks and surface clears it indicates no more reactions are occurring and to end the cook. I feel it is more reliable than string. However this requires a higher temperature and you have to remain nearby. Watching the change in the density of escaping vapor with temperature I realized it might be possible to use the vapor as temperature indicator to get to the pill stage. I selected where the distillates escaping created a light vapor which turned out to be a heating range of 395oF to 425oF. The heating time to get to the pill stage at this temperature took bout 8.5 hours, which is very good. Heating was stopped and started once during the process. The varnish consisted of 8g of Kremer linseed oil, 15g WW grade rosin (water white) and about an inch squeezed from Burnt Umber tube pigment all mixed at the start. After cooling it was thinned with turpentine to stick drip and smear on glass was tack free in 8-10 hours. The sequence of bead drops in the photo show the changes during heating, thickening so less tendency to flatten, becoming less tacky to ultimately tackles in bead 10. At this stage the surface was developing a skin around the rim indicating gelling of the oil. The heating could have been stopped at bead 9 which was slightly soft but tackles. The 3 smears on the glass show the deepening of the color with coats, and I think the final color on wood could be done in 3-4 coats. The heating set up is a 750 watt burner, a piece of aluminum flashing over the coil to help spread heat, a cut down can in case of any leakage, crumpled aluminum foil to plug the space in the outer bottom of the jar. The jar is a 4 oz baby food jar that are heat tempered. Distance from the surface of the contents to the opening of the jar has some significance in driving off substances creating tack in the finished varnish. In this set up only the very top was covered with a clear sticky substance, indicating most was blown off. With a taller container it would have remained and just refluxed in the jar and washed back into the varnish. Standing some brass screws and lining with shim stock, or copper sticks and flashing could mimic metal containers.
  4. JOHA oil varnish from International Violin Co.

    Sounds like the varnish lacks sufficient surface tension, ie, internal pull of the varnish to level itself. A varnish with adequate surface tension, you can make a smear and watch as it slowly levels and gets a uniform surface.
  5. Bass bar tuning

    Did the older bass bars also cross a few growth lines like present? I guess common sense would say they did-
  6. Varnish book, recommend or not?

    The information is a good survey of varnishes and material, a little questionable using hard copal, not easy. Unless I missed it, the most likely use of rosin as the resin is not mentioned.
  7. Maestro Sora strikes again!

    And the purfling-
  8. The Purpose of Ground?

    To me, when somebody states "ground" I consider this the mineral portion found on surfaces of the inst. The simplest answer of its presence is the results of surface preparation. Evidence this is most likely the reason is analyses has shown it is not a complete surface cover, missing in places. Logic would indicate it is the residue of sanding/preparation of the surface. A paper on making sandpaper in 1800's (lost title) said the grit was collected on the sides of roads made with Belgian stone blocks from the grinding steel of wagon wheels. It mentions it was even graded to some degree in wind rows! The other likely source of grit would be pumice. I suspect the mineral content of each differs considerably and if both were found in areas of easy procurement might indicate merely the result of sanding. (David B, anyone who uses the term "tooth" is definitely into the literature)
  9. The Purpose of Ground?

    This is from Violin Varnish by Koen Padding, it is what I believe is much of the function, to prepare a suitable varnish surface.
  10. Varnish, quick and dirty.

    Hi Jim and Ip- article is from Protective and Decorative Coatings, edited by Joseph Mattiello, 5 vols, first 3 our interest, 1940's. Invaluable. fred
  11. Colophony shelf life

    Hi all- no doubt it does not compare to fresh distilled rosin, but more to powdered rosin exposed to air for many years resulting in reduced acidity and a darker color. Substances such as oil pine, methyl alcohol, turpentine, etc are separated in collecting distilled rosin, in stump extraction these have remained and could be present. The stumps are ground up and steam distilled for the products. Obviously it you're stuck like me in staying with things available in Strad's era, you have to keep in mind it wasn't available then.
  12. Colophony shelf life

    I would be careful when trying to obtain dark rosin, for much of it is wood rosin, stuff extracted from old stumps buried in the ground. I think Kremers is wood rosin. so If you just want color and not interested in anything else I found it similar to WW grade in cooking characteristics. Russia and Latvia sell dark rosin for industrial uses such as solder flux. This is rosin distilled from live trees..
  13. Varnish on the ground or in the wood

    Sorry, accidental submit; just finishing with these are components that have been noted to be present in Cremonese varnishes. Just speculating on the function of them.
  14. Varnish on the ground or in the wood

    Just my opinion, but I feel varnish was not directily applied because soaking could result in areas that would take long periods to dry. I guess an example is the edge of the top plate. I eventually learned to only varnish sparingly because too much varnish here soaked in the vertical ends and would stay tacky long after everything else is tack free. The presence of glue- fairly common knowledge, a thin coat of glue helps to scrape or sand off the vertical projections on surfaces in preparation for getting that smooth surface necessary for the top coat. A color stain in the wood- I think this is proven, not sure- they had Brazilin, easily extracted from Pernambuco bow wood, Hematoxylon from logwood, and Alkanet from a regional weed. Anyone could be applied by including in the glue coat by adding some alcohol or lime. You also want to produce an inst that is a work of art in appearance, so anything that creates dichroism such as layering of differential coats of resin would be needed. Calcium could be present in just about any of the substances. I can't think of a specific reason for adding a layer of a mineral ground other than the remains of surface preparation.
  15. yellow ground

    Mike, I didn't realize I made the smears on a coating of saturated sol lime/glue/ alcohol/ hematoxylon. That darkened the wood. I don't think that had anything to do with the color and reflectivity of the smears. The main purpose was to just show another yellow ground.