How to make a dichromatic colored varnish

[Wm. Johnston]

The earlier topic about 'dichroic' varnish started a big long discussion. This eventually lead to this Wikipedia page that describes the effect which is also seen in certain old violin varnishes, http://en.wikipedia.org/wiki/Dichromatism

So after a little trial and error I came up with a dichromatic varnish which gives a nice color. Here is the relevant quote from the wikipedia page for figuring out how to do this, " Dichromatism is observed in any substance, that has the absorption spectrum with one wide but shallow and one narrow but deep local minimum. " This provided for me a very simple formula for producing a varnish with this property. Take a pigment with a fairly low tinting strength which has a nice red color. Combine with this a very intense, bright yellow pigment. Combine these two in the right proportions and you should get some sort of dichromatic varnish which shifts from yellow in thin coats to red in thicker ones.

How to do it,

1. Start with the red color in a paint form (for ease). I used transparent red iron oxide. Strad's varnish is known to contain red iron oxide so it must be possible to produce a dichromatic varnish using it. To this I added a very small amount of black paint to mellow out the color enough. Don't over do it with the black paint. I don't know if a red like madder would give the right effect, I haven't tried it.

2. Now on your pallet put a big gob of arylide yellow paint down. I used this since it was the brightest, strongest yellow I have. I wouldn't expect yellow iron oxide to work as well but I haven't tried. To the yellow add small amounts of the red paint. At each step test the yellow out on a piece of white paper. If you apply a little of the paint it should look yellow. Keep mixing in red paint until a thin wash of the mixture just begins to look a little orangish. The thick mass of paint on your pallet should look red or brown at this point.

3. Now take your mixture and mix it into your varnish medium.

4. Test on wood.

If you get the proportions right you should end up with a varnish with a nice color shifting property. If you didn't get it then you might have to play with the proportions of red and yellow, or try different red and yellow pigments.

I have more to say on this topic but I'll have to save it for later.

The attached picture shows a varnish made using the steps described above, it's easy. This varnish is very fresh and I think the transparency will improve in a few days.

[mayofiddler6]

The earlier topic about 'dichroic' varnish started a big long discussion. This eventually lead to this Wikipedia page that describes the effect which is also seen in certain old violin varnishes, http://en.wikipedia.org/wiki/Dichromatism

Very interesting, thanks for that. At least we all know what dichroism actually is now ( or what someone has created some formulae for and called dichroism :-) )

I assume from this explanation that your pic has layers that are getting thinner from left to right?

It's hard to understand the effects from the picture, as it just looks like the varnish is being saturated with more red. Is there some way of photographing one larger sample from different angles to show the effect taking place due to increased angle/depth of the varnish?

Good find though, lots of potential for fairly simple experiments to be made using this idea.

[Johnmasters]

Very interesting, thanks for that. At least we all know what dichroism actually is now ( or what someone has created some formulae for and called dichroism :-) )

I assume from this explanation that your pic has layers that are getting thinner from left to right?

It's hard to understand the effects from the picture, as it just looks like the varnish is being saturated with more red. Is there some way of photographing one larger sample from different angles to show the effect taking place due to increased angle/depth of the varnish?

Good find though, lots of potential for fairly simple experiments to be made using this idea.

You may or may not have seen the Lycurgus Cup. I think that this is interesting enough to post in two threads.

[Wm. Johnston]

I assume from this explanation that your pic has layers that are getting thinner from left to right?

It's hard to understand the effects from the picture, as it just looks like the varnish is being saturated with more red. Is there some way of photographing one larger sample from different angles to show the effect taking place due to increased angle/depth of the varnish?

Yes this was all done with the same varnish but in layers of varying thicknesses except that the top half was applied over a yellow base varnish. The bottom half was not.

I think what is going on is that since this uses a fairly strong yellow pigment, the yellow of the varnish essentially reaches maximum yellowness quite quickly. The red on the other hand takes a larger thickness in order to show up as red. So combine the two and you get a varnish which starts off yellow but turns orange and red with thicker layers.

The effect looks quite different than simply applying madder red over a yellow ground. In that case you can easily see where the yellow ends and the red begins. In the varnish I posted there is no dividing line, just a gradual transition.

Here is a picture from a different angle but because it was taken in diffuse light there isn't much color change with changing angle. I'll try to take better pictures under different lighting soon. I might also apply the varnish on flamed maple next. I want to just make one large batch of colored varnish so that I don't have to remix it each time I need to varnish a violin so I'll need to test it out on something.

[Johnmasters]

I think what is going on is that since this uses a fairly strong yellow pigment, the yellow of the varnish essentially reaches maximum yellowness quite quickly. The red on the other hand takes a larger thickness in order to show up as red. So combine the two and you get a varnish which starts off yellow but turns orange and red with thicker layers.

You may or may not have seen the Lycurgus Cup.

[Wm. Johnston]

Yes I have seen it. You've posted this in three different discussions and twice here.

[Johnmasters]

Yes I have seen it. You've posted this in three different discussions and twice here.

Yes, I was waiting for a response to know if anyone saw it. You are the first to respond. Any comments?

[Wm. Johnston]

I just don't find it too exciting.

Might be relevant to my sugar/pine resin concoction. Caramel (at least in water, I don't know about in resin) is a colloid so it is made of of very small particules rather than big chunks of pigment. I don't have the time to read this whole article but I think I read about the metamaterial experiment elsewhere.

[La Folia]

The wonders of colloidal gold. Interesting. That's some piece of alchemy for that time. Apparently it's rather easy to tune the absorption spectrum.

[Johnmasters]

I just don't find it too exciting.

Might be relevant to my sugar/pine resin concoction. Caramel (at least in water, I don't know about in resin) is a colloid so it is made of of very small particules rather than big chunks of pigment. I don't have the time to read this whole article but I think I read about the metamaterial experiment elsewhere.

You are amazing. I just wanted to show the picture. This is a good piece of craft, wouldn't you agree ?

Do you have any photos of your trials on wood or maybe even a finished instrument ?

[La Folia]

There you go. There's quite a growing field in tuning optical resonance in nanoparticles. Some of the absorption spectra are interesting.

But don't get the man too excited just yet, John. We're still waiting for the magic color shift with angle. Hint: you might not see it if the light is diffuse. Likewise, you might not see it if the surface is diffuse, i.e. if you have too thin a layer on a rough surface (like wood).

[Johnmasters]

There you go. There's quite a growing field in tuning optical resonance in nanoparticles. Some of the absorption spectra are interesting.

But don't get the man too excited just yet, John. We're still waiting for the magic color shift with angle. Hint: you might not see it if the light is diffuse. Likewise, you might not see it if the surface is diffuse, i.e. if you have too thin a layer on a rough surface (like wood).

I was not expecting to get the same mechanism in wood. In fact, I posted only for the picture, which is a very famous example that some may have never seen. I have not read the article myself.

I am first experimenting with stains that will have some color without blotching. If the angle-dependence is in the varnish, then I suppose it ought to be over a pretty smooth ground.

Maybe it is a mistake to look for a single dye or varnish. There could be stages of coloring. Some have seen mercury sulfide in the varnish itself. Clearly, that is not in the wood. Other pictures indicate color in the wood. That is the first thing that interests me. After that, try other things. Hopefully after getting a repertoire of various techniques, something will come to mind... a combination of opperations.

[Wm. Johnston]

Some have seen mercury sulfide in the varnish itself. Clearly, that is not in the wood.

I've been waiting a long time for someone to mention this. I thought that it would've come up a lot sooner in one of the other discussions. I think that there may be a place for an opaque red pigment in the dichromatic varnish that I started this topic about.

Suppose you want to make a really red varnish for a violin. The method that I described is going to have an orangish tint to it due to the large amount of yellow present in the varnish, unless you make the coating pretty thick. If you wanted to shift the varnish more towards a redder color then I think the thing to do is to mix in a small amount of opaque red pigment into the last few layers. These opaque red particles could reflect a little extra red light (before the yellow reduced its intensity) to help overcome the orangeness while not adding too much opacity.

I have no intention of playing with mercury sulfide and I'm definately not going to brush it onto a violin that someone is going to press under their face and against their skin. I did do a little test with cadmium red. A small amount in the final coat seemed to help increase the redness. This is still a material that I'd rather not have on a violin so I'm going to go to the art store soon and look for a better alternative for a bright opaque red. Or it could be that a madder rich varnish for the final coat would do the job as well.

[Wm. Johnston]

Maybe it is a mistake to look for a single dye or varnish. There could be stages of coloring.

We know this to be the case from the varnish research already done. That's why I had to test my varnish on wood with a yellow base coat as well as just by itself. I wanted to see if the two layers were required for the effect or if it could be achieved through a single layer system. It worked both ways.

[Johnmasters]

We know this to be the case from the varnish research already done. That's why I had to test my varnish on wood with a yellow base coat as well as just by itself. I wanted to see if the two layers were required for the effect or if it could be achieved through a single layer system. It worked both ways.

Maybe this sort of thing would have been accepted and understood by the Ancients. Picture painters used all kinds of layerings and glazes etc. That would have been pretty much common knowledge.

The terms "violin stain" and "colored varnish" have been used too much. These are misleading and focus the mind on just one kind of process.

[Melvin Goldsmith]

I've been waiting a long time for someone to mention this. I thought that it would've come up a lot sooner in one of the other discussions. I think that there may be a place for an opaque red pigment in the dichromatic varnish that I started this topic about.

Suppose you want to make a really red varnish for a violin. The method that I described is going to have an orangish tint to it due to the large amount of yellow present in the varnish, unless you make the coating pretty thick. If you wanted to shift the varnish more towards a redder color then I think the thing to do is to mix in a small amount of opaque red pigment into the last few layers. These opaque red particles could reflect a little extra red light (before the yellow reduced its intensity) to help overcome the orangeness while not adding too much opacity.

I have no intention of playing with mercury sulfide and I'm definately not going to brush it onto a violin that someone is going to press under their face and against their skin. I did do a little test with cadmium red. A small amount in the final coat seemed to help increase the redness. This is still a material that I'd rather not have on a violin so I'm going to go to the art store soon and look for a better alternative for a bright opaque red. Or it could be that a madder rich varnish for the final coat would do the job as well.

.................................

I tried cinnabar recently. try some in clear varnish and you will see. ...It looks disapointingly dull....almost grey at levels where the varnish remains transparent. Greiner writing in the Strad says they found cinnabar in Strad's orange varnishes. I tried this and the effect with even a tiny bit of Cinnabar was quite dicroic..ie orange viewed at 90 degrees turning to red viewed as the angle increases towards 180 degrees.......You can only use a tiny amount or the varnish becomes dull and opaque....a tiny pinch of red ochre might be nicer.

[joerobson]

.................................

Greiner writing in the Strad says they found cinnabar in Strad's orange varnishes.

Melving,

No offense intended to the author but I thought the sample looked like touch up. A colleague and friend Shan Jiang [Feng's brother] gave me a hand held microscope this summer and it gives you a feel for looking at particle size in the varnish...this looks like big chunk of cinnibar to me.

Joe

[Melvin Goldsmith]

Melving,

No offense intended to the author but I thought the sample looked like touch up. A colleague and friend Shan Jiang [Feng's brother] gave me a hand held microscope this summer and it gives you a feel for looking at particle size in the varnish...this looks like big chunk of cinnibar to me.

Joe

Joe,

That's interesting.

Sounds like that hand held microsope will come in handy!

I wondered if the inclusion of cinnabar was a little alchemist spell to magically aid permanance?!....my experiments may well have been inadequate but did not pursuade me that cinnabar was the key.

[violins88]

1. I used transparent red iron oxide.

William,

What brand of transparent red iron oxide did you use and did you perform the test where you put some on a slide and view the slide with a flashlight in a darkened room?

thanks

[Andres Sender]

I believe cinnabar has been found in samples from multiple instruments at this point, I’m not sure it was even found in the Nagyvary sample (? the one examined by McCrone?), which so closely matched retouching procedures. Cinnabar was found by Echard as I recall.

Melving,

No offense intended to the author but I thought the sample looked like touch up. A colleague and friend Shan Jiang [Feng's brother] gave me a hand held microscope this summer and it gives you a feel for looking at particle size in the varnish...this looks like big chunk of cinnibar to me.

Joe

[joerobson]

I believe cinnabar has been found in samples from multiple instruments at this point, I’m not sure it was even found in the Nagyvary sample (? the one examined by McCrone?), which so closely matched retouching procedures. Cinnabar was found by Echard as I recall.

Andres,

I am always willing to be wrong. It would be interesting to see particle size in the other samples. My reaction was more to the appearance of the particle than cinnibar itself. Thanks for the info.

Joe

"As a failure, I have a long success story." Joe

[Wm. Johnston]

William,

What brand of transparent red iron oxide did you use and did you perform the test where you put some on a slide and view the slide with a flashlight in a darkened room?

thanks

I used Golden brand acrylic for the transparent red oxide. It would be more transparent in oil. That said my sample's transparency on the red side where the varnish is thick has been improving.

I don't do any tests for transparency other than checking that they are transparent enough on wood. I don't care how transparent it is in other applications. What matters is how it looks on wood. Testing samples in other ways can add additional unexpected effects.

[mayofiddler6]

You are amazing. I just wanted to show the picture. This is a good piece of craft, wouldn't you agree ?

I hadn't seen it John, and it is indeed a wonderful piece of craft. The article is interesting as well, particularly the property of light taking the shortest route when reflected. It has fascinated me for years that at the nano-scale light will always take the shortest route through a maze of mirrors, as if it tries every route first and then goes by the shortest. In fact this "trying every route before doing it" seems fundamental at the nano-scale for many things. I hope they can understand the mechanism fully and explain it before I die, I'd hate to go not knowing how it works.

Thanks for the pic and the article, great stuff. I don't know why we'd want to make invisible violins though. I suppose it would save all the tedious finishing work

[Johnmasters]

......... particularly the property of light taking the shortest route when reflected. It has fascinated me for years that at the nano-scale light will always take the shortest route through a maze of mirrors, as if it tries every route first and then goes by the shortest. This is almost completely correct. but it takes all paths AT THE SAME TIME, see below. In fact this "trying every route before doing it" seems fundamental at the nano-scale for many things. I hope they can understand the mechanism fully and explain it before I die, I'd hate to go not knowing how it works.

You are in luck, thanks to Dick Feynman .

Now you have given me a chance to speak of something REALLY interesting to me. Light takes the shortest route; always. That is the way the universe is made. If you think of light as a wave, the model is diffraction and Huygen's wavelets. This is very old physics.

Richard Feynman helped solve quantum electrodynamics for which he shared a Nobel Prize*. His approach was a Lagrangian one with a summation over all possible paths. That is where Feynman diagrams come from. He wrote a small book, "QED" which is non-mathematical and very clear.

He gives a simple example here of reflection of light from a mirror. A summation of all paths over the surface of the mirror gives phase cancelation except for paths extremely** close to the equal angles of incidence and reflection. It is a diffraction argument, but he never says this and there is no mathematics.

**The error is exactly what the diffraction model would give, of course.

Feynman was a great teacher, and probably the greatest physicist since Einstein. He was the guy who gave the very simple demonstration about the rubber O-ring problem in the televised Challenger Disaster report. Of course, any engineer could have explained it to a collegue. Feynman had a special gift to make it clear to anyone.

*I really want to explain this. He shared the prize with Tomanaga and Julian Schwinger. These two did it the hard way with a lot of line integrals and a whole lot of hair. Feynman invented his diagrams to represent the line integrals and make calculations more clear. He calculated the [known] fine structure constant to 8 decimal places. Once, at CERN, he asked the cost of a huge detector and was told "$37million." Always the wag, Feynman quipped, "Don't you trust me?"

[mayofiddler6]

John, fascinating stuff, thanks. I'll get that book for sure.

Is there a way to explain to a layman how they decide it is taking all routes at once? I know in the early days they were guessing that somehow it checked each route and then went by the fastest. That seems (slightly) more improbable than going by all at once, but how do they come to that conclusion? Is it just the only currently feasible theory?

Maybe we're getting to the stage where man can't explain things any more and we're becoming mystics again