refractive ground question

[joerobson]

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

Bruce I think what you refer to here as the 'brown layer' is called the 'stain layer' in the book...the nature of the stain is as yet undiagnosed but these days more visible under UV than visible light (at least...according to my understanding of the book). I'd have to have the book at hand to diagnose your photo by the books criteria though.

I certainly need to re read the Brandmair book a few times. Greiner summarized the Brandmair teams findings in terms of 4 layers.

1/ 'Impregnation' ....ie a protein size of some kind as yet undetermined

2/ 'Stain and pore filling'.....stain yet to be identified...pore filling maybe a wipe over of colour varnish

3/ 'Base varnish' a clear/ slightly yellow layer

4/ 'Coloured varnish'

Melving,

I don't own this book as yet...soon however... and I am looking forward to studying it in detail. However I did have several conversations with Ms. Brandmair on the subject at our recent VSA convention. After her presentation many makers assumed she had specified a "protein layer" so I need her to clarify this for me. Her response was that they had found the "presence" of protein. However the identification of amino acids is non-specific as to the source and quantity of the protein based material. { If this protein is identified as keratin [source:human skin], which is most likely in a testing situation, then other conclusions are more likely.} She urged that we not take this observation [ a microcosm] and build a method around it, especially since it is not conclusive that the material was intentional.

For my eye...I have never seen or tested a protein based application that did not mask the depth of reflectivity in the wood.

on we go,

Joe

[robertdo]

Indeed if they used mass spec or such highly sensitive method they were bound to find keratin which is the major contaminant. But it would be present at very low concentration compared with a potential protein layer applied at say 2-5% as a sealer (I believe this is what people said they used in few threads). If one takes a 3% protein gelatin solution and use 5ml in total for a violin surface of 1000 cm2 (the numbers are not right but near enough for a large approximation) then it would mean about 1-1.5microgram of gelatin (or another protein) per square mm, a huge amount compared to any keratin contamination. In fact if such a protein concentration was applied to a violin there would be no problem to see it and possibly to identify it in case it is albumin or gelatin (assuming one agrees with a stradivarius been sampled up to the bare wood).

[Melvin Goldsmith]

Melving,

I don't own this book as yet...soon however... and I am looking forward to studying it in detail. However I did have several conversations with Ms. Brandmair on the subject at our recent VSA convention. After her presentation many makers assumed she had specified a "protein layer" so I need her to clarify this for me. Her response was that they had found the "presence" of protein. However the identification of amino acids is non-specific as to the source and quantity of the protein based material. { If this protein is identified as keratin [source:human skin], which is most likely in a testing situation, then other conclusions are more likely.} She urged that we not take this observation [ a microcosm] and build a method around it, especially since it is not conclusive that the material was intentional.

For my eye...I have never seen or tested a protein based application that did not mask the depth of reflectivity in the wood.

on we go,

Joe

Hi Joe

I re read Greiner's chapter of the Stradivari Varnish book. He is quite unequivocal about the presence of protein in the wood surface. He writes

'Due to the consistency with which we were able to establish the presence of proteins in all samples across the entire production span of Stradivari's instruments and at different places on Stradivari's instruments the possibility of coincidence can be ruled out'

He goes on to say that the evidence points to a milk based protein.

He makes the case for varnish type formula itself not penetrating far into the wood by the lack of blotchiness on fronts and the lack of end grain darkening for instance on scrolls. ( The latter of which I find very significant)

It may well be that Greiner is more inclined to interpret the results from the view of his experience as a luthier compared to Brandmair's approach?

[joerobson]

Hi Joe

I re read Greiner's chapter of the Stradivari Varnish book. He is quite unequivocal about the presence of protein in the wood surface. He writes

'Due to the consistency with which we were able to establish the presence of proteins in all samples across the entire production span of Stradivari's instruments and at different places on Stradivari's instruments the possibility of coincidence can be ruled out'

He goes on to say that the evidence points to a milk based protein.

He makes the case for varnish type formula itself not penetrating far into the wood by the lack of blotchiness on fronts and the lack of end grain darkening for instance on scrolls. ( The latter of which I find very significant)

It may well be that Greiner is more inclined to interpret the results from the view of his experience as a luthier compared to Brandmair's approach?

Melving,

Interesting. First off, I will soon have a copy of this book....thanks to the generosity of a MN member who is lending me his until mine comes!

Ms. Brandmair was specific when she said they could not identify the protein they observed. So, I would read a certain amount of luthier's interpretation into Greiner's analysis. My guess is he has not had any luck controlling blotchiness with any method other than a gel or protein wash.

Roberto makes it clear that one of the issues that is unresolved is the scale of protein to other materials. For me, it continues to be a question of "show me" so I can understand. The protein applications I have seen and tried mask the wood in ways that I do not observe on the good ground. I think this masking effect is in the nature of the material itself, not in the application.

One thing that Brandmair and I immediately found in common was the nature of the varnish that was in first contact with the ground/wood.

on we go,

Joe

[joerobson]

Melving,

Interesting. First off, I will soon have a copy of this book....thanks to the generosity of a MN member who is lending me his until mine comes!

Ms. Brandmair was specific when she said they could not identify the protein they observed. So, I would read a certain amount of luthier's interpretation into Greiner's analysis. My guess is he has not had any luck controlling blotchiness with any method other than a gel or protein wash.

Roberto makes it clear that one of the issues that is unresolved is the scale of protein to other materials. For me, it continues to be a question of "show me" so I can understand. The protein applications I have seen and tried mask the wood in ways that I do not observe on the good ground. I think this masking effect is in the nature of the material itself, not in the application.

One thing that Brandmair and I immediately found in common was the nature of the varnish that was in first contact with the ground/wood.

on we go,

Joe

Here is an example of what I see in ground vs protein sealer. The ground on this maple is deeply reflective and detailed, except in the wing corner where glue was wiped on and off.

We have all seen this in trying to varnish color over a glue spot. I think the effect is more dramatic when we look at ground. Glue wash is not the only alternative for protein on the wood [milk protein would be similar to a white glue wash] but I see the results as similar.

Joe

[James M. Jones]

great pic very educational thanks Joe///// gotta love MN!

[Bruce Carlson]

great pic very educational thanks Joe///// gotta love MN!

Even Stradivari smeared his glue every now and then. Makes me feel better knowing that he may have been human.

I think it's easy to see the contrast between the glue sized wood near the purfling as compared to the rest which either soaked up varnish or a colored gound.

Bruce

[scordatura]

Kudos to Joe and Bruce. It is great to see tangible info rather than the "written theory" that we frequently see around here

[Melvin Goldsmith]

Even Stradivari smeared his glue every now and then. Makes me feel better knowing that he may have been human.

I think it's easy to see the contrast between the glue sized wood near the purfling as compared to the rest which either soaked up varnish or a colored gound.

Bruce

Bruce,

I think we had this conversation before but I am not personally convinced that this picture shows a glue stain. To me this shows an imperfect blend of wood finishing between the edge channel in this area and the rest of the fiddle..In my opinion the handling of the gouge has left a burnished surface which accepted the following finish in a different way.

[Melvin Goldsmith]

Here is an example of what I see in ground vs protein sealer. The ground on this maple is deeply reflective and detailed, except in the wing corner where glue was wiped on and off.

We have all seen this in trying to varnish color over a glue spot. I think the effect is more dramatic when we look at ground. Glue wash is not the only alternative for protein on the wood [milk protein would be similar to a white glue wash] but I see the results as similar.

Joe

Hi Joe

No offense intended and I have some beautiful varnish from you but the varnish sample you offer here is not what I would recognize in an old Cremona and a glue stain is not the same as a size..

[joerobson]

Hi Joe

No offense intended and I have some beautiful varnish from you but the varnish sample you offer here is not what I would recognize in an old Cremona and a glue stain is not the same as a size..

Melving,

That is not a varnished surface...just ground.

I realize that a glue stain is not a sizing. However as I see the surface the change of appearance is one of degree, not kind. That glue stain was wiped and then a wet towel was used to draw glue from the surface. When I started doing the ground on this I thought the glue was thoroughly removed. Wrong again...

I also know that not all the classical instruments received the same ground....many roads to roam...

on we go,

Joe

[Melvin Goldsmith]

Animal based size overlaid with auripetrum plus one coat of clear and one of madder pigment colour next to Strad... The Strad colour layer was more opaque.

[joerobson]

Animal based size overlaid with auripetrum plus one coat of clear and one of madder pigment colour next to Strad... The Strad colour layer was more opaque.

Melving,

I don't understand....what am I missing?

Joe

[joerobson]

Melving,

I don't understand....what am I missing?

Joe

oops....the picture had not loaded yet. Looks good!

The ground in my photo has a skim coat of clear rosin varnish as we use it for varnishing practice at the workshops...but all the color is in the wood/ground. Violin was white when I started...no sun tan.

on we go,

Joe

[David Beard]

Animal based size overlaid with auripetrum plus one coat of clear and one of madder pigment colour next to Strad... The Strad colour layer was more opaque.

Beautiful sample!

I'm still just experimenting with possibilities, so my actual experience is very limitied. But I find the idea of St Peter's Gold/dorata/golden tin attractive. It seems a straight foward techninique consistent with the broader and less mysterious art materials of the time. As your photo shows, the results can be very effective.

As for protein sizes, I've not experienced the cloudiness issues Joe mentions. In my little varnish experiments I've found glue size or simple egg white are both easy devices to keep oil out of the wood grain and avoid the sort of featheriness or fuziness that seems to develop when pigmented oil contacts the wood grain.

I've also thought (perhaps my imagination??) that either thin glue size or simple egg white seems to create a sort of clean optical connection between the wood and an upper layer of finish of most any kind.

Thanks for showing the picture.

[joerobson]

Beautiful sample!

I'm still just experimenting with possibilities, so my actual experience is very limitied. But I find the idea of St Peter's Gold/dorata/golden tin attractive. It seems a straight foward techninique consistent with the broader and less mysterious art materials of the time. As your photo shows, the results can be very effective.

As for protein sizes, I've not experienced the cloudiness issues Joe mentions. In my little varnish experiments I've found glue size or simple egg white are both easy devices to keep oil out of the wood grain and avoid the sort of featheriness or fuziness that seems to develop when pigmented oil contacts the wood grain.

I've also thought (perhaps my imagination??) that either thin glue size or simple egg white seems to create a sort of clean optical connection between the wood and an upper layer of finish of most any kind.

Thanks for showing the picture.

David,

No doubt that protein sizing is an effective tool for sealing the wood. Compared to many other methods it provides a clear view of the wood. What it does not do is create the internal reflectivity in the wood that I think so beautiful beneath the varnish. So many of these details remain a question of matching your taste and methods to get what you want in a varnished surface.

on we go,

Joe

[jezzupe]

Joe I appreciate those pics, I was going to explain this effect,the pics saved many words. I have many varnish jobs that look good with glue wash. Yet here again, I suppose It comes down to what one is trying to achieve. Also my glue wash is not straight glue. Interesting thread, I must addmit, I'm glad I have stepped away from the Stradavarius. Being obsessed with someone elses varnish recipe could drive a guy nuts.

[Bruce Carlson]

Bruce,

I think we had this conversation before but I am not personally convinced that this picture shows a glue stain. To me this shows an imperfect blend of wood finishing between the edge channel in this area and the rest of the fiddle..In my opinion the handling of the gouge has left a burnished surface which accepted the following finish in a different way.

Hi Melvin,

I've had the 1690 "Tuscan" violin in my hands on numerous occasions and I can guarantee it is not a burnished spot although I understand exactly what you mean. It is equally true that glue for purfling and a protein filler are two different things with completely different dilutions and functions. Your rib sample is spectacular and goes to show that there is more than one way to skin a cat! When you say auripetrum are you referring to the technique of varnishing over metal to create a gold effect or are you referring to Orpiment (and or Realgar) the arsenic compounds?

Is the size completely colorless?

The "Tuscan-Medici" quintet, which I believe this violin was originally with the tenor and the cello that are still in Florence, all have what I call a certain "black pore effect" as if Stradivari was doing something a little different and a little more agressive staining effect than his other instruments because he was under the Medici gun to finish the quintet on time. It's a real staining effect that is hard to see in other instruments by the same maker but is common to this group. This also can be seen in the 1690 "Tuscan" contralto viola. In 1987 it was a great opportunity to have these four instruments together in one exhibition.

Bruce

[fiddlecollector]

Bruce,

I think we had this conversation before but I am not personally convinced that this picture shows a glue stain. To me this shows an imperfect blend of wood finishing between the edge channel in this area and the rest of the fiddle..In my opinion the handling of the gouge has left a burnished surface which accepted the following finish in a different way.

I was going to say i wasnt convinced by the glue staining,i thought the same the first time this photo was posted. I might have different views if i saw it in person in closeup ,but i was thinking along similar lines to Melvin, it looks like what i`d see on instruments from makers who have used abrasive in the channel and smooth surfaces absorb quite differently. You can control end grain absorption on areas of a spruce top by making certain areas slightly smoother. Also if you look further inward on Bruces photo the wood/varnish looks the same as the purfling channel area with a slightly roughened grain area inbetween which makes the purfling channel stand out .

[Bruce Carlson]

I was going to say i wasnt convinced by the glue staining,i thought the same the first time this photo was posted. I might have different views if i saw it in person in closeup ,but i was thinking along similar lines to Melvin, it looks like what i`d see on instruments from makers who have used abrasive in the channel and smooth surfaces absorb quite differently. You can control end grain absorption on areas of a spruce top by making certain areas slightly smoother. Also if you look further inward on Bruces photo the wood/varnish looks the same as the purfling channel area with a slightly roughened grain area inbetween which makes the purfling channel stand out .

Well I still disagree with that judgement but I wanted Melvin to understand that a light wash with a protein based solution or whatever you want to call it is going to be quite different than a glue smudge.

I don't know if I can get a better shot of it unless I do it next time I'm in Rome.

Bruce

[David Burgess]

I was going to say i wasnt convinced by the glue staining,i thought the same the first time this photo was posted. I might have different views if i saw it in person in closeup ,but i was thinking along similar lines to Melvin, it looks like what i`d see on instruments from makers who have used abrasive in the channel and smooth surfaces absorb quite differently. You can control end grain absorption on areas of a spruce top by making certain areas slightly smoother. Also if you look further inward on Bruces photo the wood/varnish looks the same as the purfling channel area with a slightly roughened grain area inbetween which makes the purfling channel stand out .

I suppose there's no way to know what it is for sure, but from the photo, it very much resembles what I get with some glue contamination.

[Brian McLinden]

COMMENTS by Joe Robson:

"For my eye...I have never seen or tested a protein based application that did not mask the depth of reflectivity in the wood."

"No doubt that protein sizing is an effective tool for sealing the wood. Compared to many other methods it provides a clear view of the wood. What it does not do is create the internal reflectivity in the wood that I think so beautiful beneath the varnish."

"No doubt that protein sizing is an effective tool for sealing the wood. Compared to many other methods it provides a clear view of the wood. What it does not do is create the internal reflectivity in the wood that I think so beautiful beneath the varnish. So many of these details remain a question of matching your taste and methods to get what you want in a varnished surface."

+ + + + + + + + + +

The reflectivity that Joe mentions remains an open question, and if I remember correctly, Joe has also implied coloring at the wood/ground interface - and no sun tan.

Isn't gypsum synthesized in situ highly reflective?

Since ample copper has been found in several master violins, and since Sacconi spoke about a "process of oxidation" in connection with the ground (not varnish), I wonder if some sort of "mineral dyeing" process involving copper acetate might account in part for the wood's observed internal reflectivity?

+ + + + + + +

More from Joe Robson (from another thread) -- "The infamous "turkey red" enters into the mix. However what is of more importance to us is the way the oranges and purples were developed. Trumping that...how did they get it to fix on the fiber in such a permanent way?" [my italics added]

I attach significance to Joe's word choice.

[MikeC]

Animal based size overlaid with auripetrum plus one coat of clear and one of madder pigment colour next to Strad... The Strad colour layer was more opaque.

Is this a real Strad? If so the color looks a lot different than the usual over saturated color in pictures that you usually see, Thanks for posting that!

Also the top looks very smooth, no corduroy that I can see. Does that mean it was smoothed when it was first made or that the groves were later filled in by what ever was applied for polishing? Or is the resolution of the photo just not enough to show the texture?

[MikeC]

Brian McLinden-

I wonder if some sort of "mineral dyeing" process involving copper acetate might account in part for the wood's observed internal reflectivity?

Isn't copper acetate a blueish greenish color?

[Brian McLinden]

Brian McLinden-

I wonder if some sort of "mineral dyeing" process involving copper acetate might account in part for the wood's observed internal reflectivity?

Isn't copper acetate a blueish greenish color?

I believe it most certainly is - as a reagent.

But you get a nice orange brown if you apply it to pine and follow by a peroxide. Of course the Cremonese had alternative means of oxidation...