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Wm. Johnston

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Everything posted by Wm. Johnston

  1. Pressure treated wood? Sure looks like tulip poplar to me.
  2. When I saw the color of your wood I immediately thought that this looked like California Redwood. The comment about there not being any cedar smell makes me even more inclined to think it's Redwood.
  3. Leaving aside whether it will cause hardening, the ph of the lime will cause the wood to turn a yellowish color that will not happen with calcium sulfate.
  4. It shouldn't be too hard to estimate how wide the trees used by the old makers were. This picture doesn't have the correct lighting but a shot from this angle with lighting that shows the grain on the spruce should work, http://collections.nmmusd.org/Violins/Stradivari3598/3598StradviolinbottomribbuttonLG.jpg From a shot like this it should be possible to measure the curvature of the growth rings which would then give you an estimate of the tree's diameter. Of course trees are never perfectly round but after looking at enough violins a trend will probably be apparent. As a practical matter if the spruce comes from a small tree then the rings will have a lot of curvature to them when viewed from the bottom of the rough cut wedges. As you carve an arch into the spruce the grain lines will look curvy when you view the plate from the front. So, if you like your grain perfectly straight you should use spruce from a large tree.
  5. I'm more interested in the reason for the angled scroll. Can't believe I missed it the first time I looked at the picture.
  6. You can buy paints and pigments that are based on interference. I know Golden makes a line of acrylic paints with these pigments, you could probably find someone that makes them in oil paint and then mix them into the varnish. It probably wouldn't look too good.
  7. Aniline dyes have over 100 years of use showing that they are fugitive and should be avoided. There are modern alternatives, like Transtint, that are completely transparent and lightfast.
  8. Well, if you are confident in your ability to clean up a cnc carved scroll then things go very fast. The last time that I did this it took me ~1hour to cnc the scroll and about an hour to carve it down to a look that I liked with small gouges. Then gave it ~30 minutes for a quick cleanup prior to varnishing.
  9. No, being a great salesman is a completely different talent than being a great violinmaker. You could be the greatest violinmaker who ever lived but if you also happen to be an inept salesman no one will even notice you. On the other hand, a mediocre violinmaker who is a great salesman will do quite well in their lifetime. After they are gone, and there is no one to promote their work, then opinion of them will probably decline. We like to think that all we have to be is a great craftsman and hoards of violinists will be lining up to order from us but that's just a pipedream.
  10. The last time I turned my blacklights on to dry something they produced a very noticeable ozone smell. I blamed the power supplies, not the bulbs, but I have no proof that is where the smell was actually produced. I just sniffed around and the smell was strongest at the power supplies.
  11. It is. The strength of the effect will depend on the CT scanner used, its software, scan parameters... but these lines are visible in scans of other violins.
  12. It's an artifact of how the scanning works. The lines being discussed are essentially elevation contours for the arches of the plate. Think about it this way. The CT scanner is taking scans of the violin along well defined directions and positions and then piecing them together to form an image of the entire violin. There are bound to be small artifacts at the places where the data gets stitched together.
  13. I'm not sure what the rectangles are supposed to represent but I think it is more helpful to just draw a few lines and see how the f-holes fit onto the rest of the violin. Whether or not this is the method that was used to select their position doesn't matter to me. I'm just interested in why they work visually on these particular violins. On the attached pictures I've drawn lines between the purfling miters, the widest portion of the lower bout and a point approximately at the end of a modern fingerboard. On Strad and early del Gesu violins the line between the widest points of the lower bout and the upper f-hole eyes points to the end of a modern length fingerboard*. On a late del Gesu they tend to point more towards the line joining the purfling miters. It's interesting that the lower eyes usually also fall on these lines and that the arm connecting the two holes is approximately tangent to this connecting line. Anyways, I've found that drawing these few lines on a violin helps a lot with getting reasonable f-hole placements relative to the rest of the outline, especially where you are not producing a copy of an old violin. *Of course these violins didn't have modern fingerboards when they were built but this might be a clue why the modern fingerboard looks good on an instrument that was meant to have a short one.
  14. I've built violins where my purfling ended up looking like this and I always scrape it flush to the spruce or maple. My ground contains water and it causes the purfling to swell more than the surrounding wood.
  15. It looks like this is just due to texture. The hard late growth lines have soaked up less varnish or were smoother before varnishing. After varnishing the late growth has a smooth varnish that produces specular reflection, the softer earlier growth has a rougher surface and is giving diffuse reflection. Unrelated to dichromatism. At least that is how it looks to me in the pictures.
  16. The sensitivity of your camera's chip is fairly easy to figure out. Look up your camera's information sheet, figure out the model of the CMOS (or CCD) chip inside, google that to find the chip's datasheet, and it will most likely be there. What would worry me is the processing done inside the camera. Pictures are normally saved as jpegs so there is image compression going on plus whatever on the fly adjustments are done to the image to make it look better. It would be better to use a simple camera like the ones used for digital astrophotography. Those ones save a non-compressed bitmap image that is easy to work with in programs like Matlab. Plus it is super easy to find spectral information for the chips inside them. If you are electronically inclined there are small integrated circuits with pin diodes and multiple color filters that are designed specifically for colorimetry.
  17. How about the pictures at the beginning of this thread? http://www.maestronet.com/forum/index.php?/topic/320397-how-to-make-a-dichromatic-colored-varnish/ In this thread I made a dichromatic varnish by mixing several colors that were not individually dichromatic.
  18. I think that lighting intensity could have an affect on the color seen in varnish since different receptors in your eye have different sensitivities. The red receptors in your eye work poorly in low light so I would expect varnish to look less red and more brown, orange, or yellow as the light is dimmed. This would be purely due to how the human eye works, the color measured by a spectrometer or colorimeter would be the same regardless of the intensity.
  19. Dichromatism, https://en.wikipedia.org/wiki/Dichromatism
  20. This looks roughly correct for a violin of 1600 to 1700. Attached is a detailed photo of a Dutch painting from the Rijksmuseum of a violin in a Dutch still life painting from the period. Not an exact match but you can see that fingerboards were a lot shorter then. This violin looks like what you would expect from an early 1600s Amati or other Italian violin. Violins from other places might have the fingerboard done up a bit differently.
  21. If anyone gave you a 'yes, it will work great' or a 'no, it will be horrible' answer based on this one number then, in my opinion, they are best ignored. Now if the spruce had a density of 0.68 then it would be unusual enough to disqualify it but 0.68 is not too unusual for red or sugar maples and they can work just fine. Plenty of instruments are made using wood that a particular maker would frown upon, for some reason, but other makers get good results from.
  22. I would use it. Unless the wood has low stiffness I bet it can be made to work. The best way to find out is to carve a plate from it and see if it feels right or if it feels like wet cardboard.
  23. Wasn't that how del Gesu treated his corners? On the originals this feature has mostly worn away, my guess is that this violin is trying to mimic this feature but ended up greatly exaggerating it.
  24. I hadn't heard of an Amati viola book, do you have a link?
  25. I timed myself doing this twice. Every 15 minutes or 2 hours of work on the violins was written down but I only recorded actual hands on time, glue and varnish drying was not included. Both times I spent 80 hours building a violin.
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