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On 8/30/2018 at 7:50 PM, joerobson said:

Ernie,

This varnish is quite translucent but the color is extremely strong.

Joe

 

Joe,

In your article, you attribute the color changing properties of your varnish to the strength of the lighting. You say that under diffuse lighting conditions, the varnish appears red but strong light has the power to penetrate to the lower layers and produce a more yellow cast.

Is this how you explain the so-called dichroism of the Cremonese varnishes?

Years ago, in the museum in Mittenwald, there was a modern violin on a rotating stand and as it turned the varnish went from yellow to a kind of magenta color. Clever but not very attractive. However, it was intended to show the phenomenon of optical dichroism as a function of the angle of the light relative to the violin and not the intensity of it.

Glenn

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On 9/5/2018 at 7:29 AM, GlennYorkPA said:

Joe,

In your article, you attribute the color changing properties of your varnish to the strength of the lighting. You say that under diffuse lighting conditions, the varnish appears red but strong light has the power to penetrate to the lower layers and produce a more yellow cast.

Is this how you explain the so-called dichroism of the Cremonese varnishes?

Years ago, in the museum in Mittenwald, there was a modern violin on a rotating stand and as it turned the varnish went from yellow to a kind of magenta color. Clever but not very attractive. However, it was intended to show the phenomenon of optical dichroism as a function of the angle of the light relative to the violin and not the intensity of it.

Glenn

 

10 hours ago, GlennYorkPA said:

It's only the correct term when discussing dichromatism.

This is not the phenomenon I was discussing nor what Joe described in his article. We are referring to optical dichroism.

If you need definitions of the terms, I'm happy to oblige.

Glenn

Glenn,

Please make your case.

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12 hours ago, Michael_Molnar said:

 

Glenn,

Please make your case.

OK. Let me try and keep it simple.

Dichromatism is perhaps the easiest to describe and dismiss.

It is a phenomenon whereby the perceived color or hue changes as the layer thickness varies. So maybe a very thin layer looks green but then appears to change to blue as the layer gets thicker. This is not angle dependent and can be seen by light transmitted through the layer at a 90 degree incidence angle. In fact, this phenomenon is quite rare and was only explained scientifically fairly recently.

Optical dichroism is where the perceived color changes according to the viewing angle. So a layer of constant thickness may appear one color when viewed at one angle and a different color at a different angle. (There is a commercially available decorative plastic film which changes from yellow to magenta as you play with the angle. It used to be used on Dove soap packaging to give a pearly effect. The violin I saw in Mittenwald looked exactly like that).

What Joe described in his article in The Strad was neither of these but it was closer to the second option. He considers two layers, a yellow one (the ground) and a red one (his red cochineal varnish). His contention is that under low light only the red of the varnish layer is seen. But under strong light, the light is able to penetrate the red layer and pick up the yellow tone of the underlayer. (He has photos demonstrating this).

I hope this helps.

G;enn

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12 hours ago, GlennYorkPA said:

OK. Let me try and keep it simple.

Dichromatism is perhaps the easiest to describe and dismiss.

It is a phenomenon whereby the perceived color or hue changes as the layer thickness varies. So maybe a very thin layer looks green but then appears to change to blue as the layer gets thicker. This is not angle dependent and can be seen by light transmitted through the layer at a 90 degree incidence angle. In fact, this phenomenon is quite rare and was only explained scientifically fairly recently.

Optical dichroism is where the perceived color changes according to the viewing angle. So a layer of constant thickness may appear one color when viewed at one angle and a different color at a different angle. (There is a commercially available decorative plastic film which changes from yellow to magenta as you play with the angle. It used to be used on Dove soap packaging to give a pearly effect. The violin I saw in Mittenwald looked exactly like that).

What Joe described in his article in The Strad was neither of these but it was closer to the second option. He considers two layers, a yellow one (the ground) and a red one (his red cochineal varnish). His contention is that under low light only the red of the varnish layer is seen. But under strong light, the light is able to penetrate the red layer and pick up the yellow tone of the underlayer. (He has photos demonstrating this).

I hope this helps.

G;enn

Your definitions are incomplete which leads to your incorrect characterization. Dichroism needs a molecular thin layer to produce an angle-dependent optical wave interference pattern of colors. The constructive/destructive wave interference produces colors. Oil films on water are the best example. Varnish layers are orders of magnitude too thick for dichroic effects.

Dichromatism involves the color-dependent absorption of the varnish (pigments or dyes) coupled to the human-eye sensitivity and response: We see in three colors and in "factors", "powers", or "orders of magnitude" (non-linear logarithmic scale). As the absorption of a dichromatic layer is increased either by the viewing angle or different layer thickness,  the yellow color falls off faster than the red due to our non-linear eye-response and 3 color-band sensitivity. Thus, a thin dichromatic layer will look bright yellow and a thicker layer looks redder but darker. Check the illustrations on Wikipedia

I also disagree with your interpretation of what Joe wrote, but I hope he will explain what he meant. 

Hope this helps.

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  • 5 months later...

Well it is workshop season once again.  I'm in the midst of preparing a series of 5 instruments to illustrate the differing effects of application, separator coat and polishing. 

The spring workshop is set for April 27th - May 4th at the Chicago School of Violin Making. If you are interested let me know! 

The first Varnish 101 workshop at Learning Trade Secrets was a pleasure and a success.  It differs a lot from our CSVM workshop [which is a very comprehensive approach]....a narrower focus and attention to the basics of oil varnish application.  I stress the necessity of being able to do a "4 and out" varnish job.  Over the ground: 1 coat of clear, 2 coats of color, 1 coat of clear as the necessary skill to develop a personal style of varnishing.

More photos as the series develops.

on we go,

Joe

Violin Varnish Workshops.doc

room.jpg

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  • 1 month later...
  • 1 month later...
18 hours ago, lpr5184 said:

I see Tommy Coleman was there. What's the story with the colored fiddles Joe?

He was indeed!  It was very informative and interesting. Thanks Joe!  The colored fiddles were a whimsical project by a shop owner.  Her shop is really neat and decorated and if you ever visited it you would see how well these would fit in. 

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On 5/10/2019 at 1:49 PM, lpr5184 said:

I see Tommy Coleman was there. What's the story with the colored fiddles Joe?

Kory....Korinthian Violins in Milwaukee.

She is a regular participant and always has interesting and difficult projects....the Workshop is a good place for both.

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OK...I didn't think the color was your product but one never knows...I see that dyed look on solid body electric guitars built from bigleaf maple and electric violins are colorful but I've never seen someone do that to a bench made instrument. Must not have been one of hers.

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2 hours ago, lpr5184 said:

OK...I didn't think the color was your product but one never knows...I see that dyed look on solid body electric guitars built from bigleaf maple and electric violins are colorful but I've never seen someone do that to a bench made instrument. Must not have been one of hers.

They are cheap Chinese instruments.

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