Wm. Johnston

Members
  • Content count

    2095
  • Joined

  • Last visited

About Wm. Johnston

  • Rank
    Enthusiast
  • Birthday May 8

Contact Methods

  • Website URL
    http://www.johnstonviolins.com
  • ICQ
    0

Profile Information

  • Gender
    Male
  • Location
    Floodzone, Southeast Texas

Recent Profile Visitors

9816 profile views
  1. Cedar top repair question

    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.
  2. Kremer's new violin ground

    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.
  3. Spruce grain

    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.
  4. 8 violin clips for tone evaluation

    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.
  5. Wild Turkeys, varnish and structural color

    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.
  6. Aniline dyes ?

    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.
  7. machine made violins also CNC "Betts"

    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.
  8. mysterious secrets of new violins

    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.
  9. Actual dangers of UV cabinet on health (not counting eyes)

    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.
  10. Stradivari Betts violin

    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.
  11. Stradivari Betts violin

    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.
  12. Guarneri F-hole placement

    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.
  13. 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.
  14. 'Dichroism'; in the ground or 'varnish'?

    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.
  15. 'Dichroism'; in the ground or 'varnish'?

    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.