Stradivari Varnish oil/resin ratio


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1 minute ago, sospiri said:

Thick hard shellac just turns the instrument into a screechbox. If it's very thin, that would be a different matter. This is the difference between French polishing which requires considerable skill and experience and brushed on shellac.

You didn’t answer my question.

There are plenty of ways to turn an instrument into a “screechbox”.
 

What’s thick?  What’s thin...?

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1 minute ago, Mark Norfleet said:

You didn’t answer my question.

There are plenty of ways to turn an instrument into a “screechbox”.
 

What’s thick?  What’s thin...?

Well I was responding to your response to another poster and I jumped in....

What's thick? What's thin.....well you're gonna have to learn the art of French Polishing yourself to figure that out. I never mastered it so my attempts were usually too thick.

 

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17 minutes ago, sospiri said:

Well I was responding to your response to another poster and I jumped in....

What's thick? What's thin.....well you're gonna have to learn the art of French Polishing yourself to figure that out. I never mastered it so my attempts were usually too thick.

 

So you did.  My apologies, I read too quickly and saw the Ss and assumed....

I'll still question your contention that "Thick hard shellac just turns the instrument into a screechbox", but will leave it at that as I'm not eager to dilute the value of this thread.  
 

I'll look into learning about "French Polishing".  YouTube perhaps...

 

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17 minutes ago, sospiri said:

Well I was responding to your response to another poster and I jumped in....

What's thick? What's thin.....well you're gonna have to learn the art of French Polishing yourself to figure that out. I never mastered it so my attempts were usually too thick.

 

just to help you out a little bit one could french polish 20 coats of finish and still rub through to ground when it's polishing time.  Now with a brush one could put an equivalent of 50 coats of polish in one swoosh of the brush.  As you were.......

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Dear friends,

Finally I arrived at a stage where I would like to share and discuss my thoughts about the following publications:

  • B Brandmair, SP Greiner „Stradivari varnish“
  • J-P Echard, S Vaidelich et al; „The Nature of the Extraordinary Finish of Stradivari’s Instruments“; Angew. Chem. Int. Ed. 2010, 49, 197-201
  • CY Barlow and J Woodhouse; „Of old wood and varnish: Peering into the can of worms“ JCAS Vol 1 no. 4 (Series II) Nov 1989 pp2-9

First of all, I would like to explain the very basics of the used and discussed methods:

FTIR: Fourier transformation of infrared spectra. Objects are irradiated by blackbody radiators. The specific absorption spectrums are analyzed and help to identify especially OH, C=O and CH2/CH3 groups.

Scanning Electron Microscope (SEM): Electrons are fired at an object, a very sharp picture is achieved. Conductive coating and vacuum are needed.

SEM/EDX: The electrons fired at a sample induce electromagnetic radiation (x-rays) with specific spectra, depending on the atoms. The radiation spectrum is detected and analyzed by its peak distribution. This method CANNOT detect atoms with lower atomic number than sodium. That means, that for example carbon, hydrogen nor oxygen can be detected by this method. (This point will be important later on, since these are by far the main components of colophony and linseed oil)

 

Let’s start with the naked results without any interpretation.

1. Brandmair & Greiner

B&G compared the FTIR spectra of fresh applied varnish made by Stephan Peter Greiner to the Strad varnished. Greiner made several varnishes with different oil:resin ratios. The FTIR of Greiners 80:20 varnish (final and applied product) matched best to the Strad FTIR spectrum. 

UV and vis microscopy could not identify filler-type particles within the ground layer. SEM pictures were not provided in the book.

Side note: UV and Vis microscopy can not identify colloidal suspensions of very small particles, they would appear as a homogenic mass. Brandmair also commented about this issue in the pigment chapter.

 

2. Barlow and Woodhouse

IMG_0522.thumb.jpg.d4751b254520957339a7a8b01961821e.jpg

This is the only SEM picture provided in the publication, which can be attributed to Stradivari with sufficient confidence.

I colored the left side to discern between the different layers. They found a very basic porous layer (red). There are almost no particles penetrating the porous structure. Then there is a ca. 60 µm thick layer (green colored). It appears inhomogenic, with amorphous particles of different sizes between 1 µm up to around 10 µm. A third layer (blue colored) sits on top of that, it is around 2 µm thick and appears quite homogenic.

 

In the SEM/EDX different minerals were found. Please keep in mind, they can not provide information, if and how much of organic material is in the sample due to the method. So, the varnish/resin content within this particulate matter can not be provided.

 

3. Echard et al

IMG_0523.jpg.e271d73b76fd89e4a8e6756a6d771d6b.jpg

UV-Microscopy shows three different layers. The lowest one being the wood, covered with a green-whitish fluorescing layer and the top layer with yellow-salmon like fluorescence patterns.

Here are the according FTIR spectra of the three layers.

IMG_0524.thumb.jpg.a28e52aa443ceeb336e0947462d40482.jpg

The main difference lies in the OH-band, which is very weak in the lower varnish layer. Echard stated this to be the lower varnish layer, comprising of pure linseed oil.

My interpretation of the results

You all know the interpretation of the authors, so I left it out. First of all, let us begin with the SEM picture of Barlow/Woodhouse. They state that the bottom layer (red) is wood, the middle (green) being the particulate mineral ground, and the blue colored stratum should be the color varnish, which was in their opinion almost gone (but they stated about the same sample that it had a striking brownish color).

If you assume that the middle layer are the varnish layers, the thin top layer (blue) could be a restorers french polish. The middle stratum with around 50-70 µm does not appear way too thin to be a full varnish layer.

Barlow/Woodhouse did not perform an FTIR analysis on this layer, only SEM/EDX. Therefore, there is lacking evidence against the middle stratum being a varnish layer without a mineral filler.

 

What if the middle layer (green) would be the actual varnish, for example a cold-combined high-resin low-oil varnish. This would be rather a colloidal suspension of oil and amorphous colophony particles than a solid („firm pill stage“) varnish. You could easily obtain a SEM/EDX spectrum like the one Barlow measured. You still would not know if it is 0,1% Si and 99,9% organic material.

So, with the lacking FTIR, the Barlow/Woodhouse results could also fit my interpretation.

Echard et al. In contrast did an FTIR of the base layer stating that this would be pure drying oil. I do not disagree with their results, the FTIR fits (if the base varnish has not treated with a lye).

 

If I make a cold mixed varnish and put a drop on a paper, the colophony stays where it is, the oil soaks in the circumference of the paper. So the varnish disarranges - drying oil leaves the varnish and soaks into the wooetd. Et voila, here we have the pure drying oil as a base coat layer in the varnish. After the solvent evaporates, the dissolved colophony may form small amorphous particles surrounded by linseed oil.

 

And what about B&G? They did not found a mineral layer in the base coat and used FTIR AND SEM/EDX. On the other hand, uv- and vis-microscopy would be too low in resolution to show the varnish actually as it is - a suspension of colophony particles and dried linseed oil.

 

I have the lack of a modeled experiment to approve these claims. I would need to apply cold-combined varnish on a well prepared wood and let it polymerize. After a bit of aging, SEM, SEM/EDX and FTIR needs to be done on my prepared samples. If they would match, this could support my theory. Until then this is not more than a humble theory.

 

I would enjoy any comment about this.

Michael

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22 hours ago, Mark Norfleet said:

 

I'll look into learning about "French Polishing".  YouTube perhaps...

 

:lol:

The reason this this strikes me as funny is that Norfleet is a highly experienced and respected restorer, and already knows more about French Polishing than just about anybody.

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Your middle layer of the Barlow & Woodhouse picture is a mineral layer.  The EDAX data proves this to be the case.  The authors mention that the region seems to be mostly devoid of varnish.  

Cold-mixture of oil and resin to make a varnish?  Where does this come from?  

I looked at some FTIR data for a different cooked varnishes going from 1:1 to 1:3 oil:rosin (Echard work as I recall).  It was really hard to see any difference in the FTIR responses.  If this is really true, it casts double on the B&G conclusions on oil;resin ratio in the varnish.

Too much "magical thinking" for me.  I give up.

Mike D

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13 hours ago, Michael Szyper said:

Dear friends,

Finally I arrived at a stage where I would like to share and discuss my thoughts about the following publications:

...

Thanks Michael for exposing your impressions so in depth, much appreciated.

I quite agree with your conclusions, especially those about Barlow and Woodhouse: it has always seemed unlikely to me that the thick layer they identify could only be a mineral ground, that it was instead the actual varnish, for me is much more likely.

Even your hypothesis to justify the oil in the wood found by Echard seems interesting and sensible to me.

A cold-mixed varnish, or at least made at low temperature (100/120 °) cannot be discarded a priori for ancient varnishes (we will simply never know for sure) and would open a new perspective on whether luthiers have made their varnishes themself or not.

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It seems a little unfortunate to me that studies like these, fascinating and important as they are, seem to lead to large numbers of makers using the same (or very similar) varnish formulations, right down to the pigment du jour (cochineal, of course). All our fiddles are going to end up  looking the same! :D

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30 minutes ago, Bodacious Cowboy said:

It seems a little unfortunate to me that studies like these, fascinating and important as they are, seem to lead to large numbers of makers using the same (or very similar) varnish formulations, right down to the pigment du jour (cochineal, of course). All our fiddles are going to end up  looking the same! :D

I been reading along all the while.  Seems to me it leads to what I do for making varnish which is the Ch. Reade way of doing things along with the poor man adjustment method applied by myself. 

I have no clue to what the ground layer could be?  Gamboge in alcohol or egg white - take your pick.  Who knows.

Greiner could heat up alcohol and spirits of turps, then add colophony afterwards.  How he would go about getting acceptable shades of red/brown would be the expensive lesson.

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36 minutes ago, Bodacious Cowboy said:

It seems a little unfortunate to me that studies like these, fascinating and important as they are, seem to lead to large numbers of makers using the same (or very similar) varnish formulations, right down to the pigment du jour (cochineal, of course). All our fiddles are going to end up  looking the same! :D

Not really. Temperature should be considered an ingredient, and application method makes a huge difference.  Both will vary within maker over time, and more so among makers using the same recipe. Let alone all personal tweaks to the recipe that are inevitable. 

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1 hour ago, Bodacious Cowboy said:

It seems a little unfortunate to me that studies like these, fascinating and important as they are, seem to lead to large numbers of makers using the same (or very similar) varnish formulations, right down to the pigment du jour (cochineal, of course). All our fiddles are going to end up  looking the same! :D

I will somewhat agree. Easy international travel (at least prior to the coronavirus) combined with the main sources of teaching these days, have tended to blurr regional differences.

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15 hours ago, David Burgess said:

:lol:

The reason this this strikes me as funny is that Norfleet is a highly experienced and respected restorer, and already knows more about French Polishing than just about anybody.

That's a relief to know he won't be turning good instruments into screechboxes.

 

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18 hours ago, Michael Szyper said:

Dear friends,

Finally I arrived at a stage where I would like to share and discuss my thoughts about the following publications:

  • B Brandmair, SP Greiner „Stradivari varnish“
  • J-P Echard, S Vaidelich et al; „The Nature of the Extraordinary Finish of Stradivari’s Instruments“; Angew. Chem. Int. Ed. 2010, 49, 197-201
  • CY Barlow and J Woodhouse; „Of old wood and varnish: Peering into the can of worms“ JCAS Vol 1 no. 4 (Series II) Nov 1989 pp2-9

First of all, I would like to explain the very basics of the used and discussed methods:

FTIR: Fourier transformation of infrared spectra. Objects are irradiated by blackbody radiators. The specific absorption spectrums are analyzed and help to identify especially OH, C=O and CH2/CH3 groups.

Scanning Electron Microscope (SEM): Electrons are fired at an object, a very sharp picture is achieved. Conductive coating and vacuum are needed.

SEM/EDX: The electrons fired at a sample induce electromagnetic radiation (x-rays) with specific spectra, depending on the atoms. The radiation spectrum is detected and analyzed by its peak distribution. This method CANNOT detect atoms with lower atomic number than sodium. That means, that for example carbon, hydrogen nor oxygen can be detected by this method. (This point will be important later on, since these are by far the main components of colophony and linseed oil)

 

Let’s start with the naked results without any interpretation.

1. Brandmair & Greiner

B&G compared the FTIR spectra of fresh applied varnish made by Stephan Peter Greiner to the Strad varnished. Greiner made several varnishes with different oil:resin ratios. The FTIR of Greiners 80:20 varnish (final and applied product) matched best to the Strad FTIR spectrum. 

UV and vis microscopy could not identify filler-type particles within the ground layer. SEM pictures were not provided in the book.

Side note: UV and Vis microscopy can not identify colloidal suspensions of very small particles, they would appear as a homogenic mass. Brandmair also commented about this issue in the pigment chapter.

 

2. Barlow and Woodhouse

IMG_0522.thumb.jpg.d4751b254520957339a7a8b01961821e.jpg

This is the only SEM picture provided in the publication, which can be attributed to Stradivari with sufficient confidence.

I colored the left side to discern between the different layers. They found a very basic porous layer (red). There are almost no particles penetrating the porous structure. Then there is a ca. 60 µm thick layer (green colored). It appears inhomogenic, with amorphous particles of different sizes between 1 µm up to around 10 µm. A third layer (blue colored) sits on top of that, it is around 2 µm thick and appears quite homogenic.

 

In the SEM/EDX different minerals were found. Please keep in mind, they can not provide information, if and how much of organic material is in the sample due to the method. So, the varnish/resin content within this particulate matter can not be provided.

 

3. Echard et al

IMG_0523.jpg.e271d73b76fd89e4a8e6756a6d771d6b.jpg

UV-Microscopy shows three different layers. The lowest one being the wood, covered with a green-whitish fluorescing layer and the top layer with yellow-salmon like fluorescence patterns.

Here are the according FTIR spectra of the three layers.

IMG_0524.thumb.jpg.a28e52aa443ceeb336e0947462d40482.jpg

The main difference lies in the OH-band, which is very weak in the lower varnish layer. Echard stated this to be the lower varnish layer, comprising of pure linseed oil.

My interpretation of the results

You all know the interpretation of the authors, so I left it out. First of all, let us begin with the SEM picture of Barlow/Woodhouse. They state that the bottom layer (red) is wood, the middle (green) being the particulate mineral ground, and the blue colored stratum should be the color varnish, which was in their opinion almost gone (but they stated about the same sample that it had a striking brownish color).

If you assume that the middle layer are the varnish layers, the thin top layer (blue) could be a restorers french polish. The middle stratum with around 50-70 µm does not appear way too thin to be a full varnish layer.

Barlow/Woodhouse did not perform an FTIR analysis on this layer, only SEM/EDX. Therefore, there is lacking evidence against the middle stratum being a varnish layer without a mineral filler.

 

What if the middle layer (green) would be the actual varnish, for example a cold-combined high-resin low-oil varnish. This would be rather a colloidal suspension of oil and amorphous colophony particles than a solid („firm pill stage“) varnish. You could easily obtain a SEM/EDX spectrum like the one Barlow measured. You still would not know if it is 0,1% Si and 99,9% organic material.

So, with the lacking FTIR, the Barlow/Woodhouse results could also fit my interpretation.

Echard et al. In contrast did an FTIR of the base layer stating that this would be pure drying oil. I do not disagree with their results, the FTIR fits (if the base varnish has not treated with a lye).

 

If I make a cold mixed varnish and put a drop on a paper, the colophony stays where it is, the oil soaks in the circumference of the paper. So the varnish disarranges - drying oil leaves the varnish and soaks into the wooetd. Et voila, here we have the pure drying oil as a base coat layer in the varnish. After the solvent evaporates, the dissolved colophony may form small amorphous particles surrounded by linseed oil.

 

And what about B&G? They did not found a mineral layer in the base coat and used FTIR AND SEM/EDX. On the other hand, uv- and vis-microscopy would be too low in resolution to show the varnish actually as it is - a suspension of colophony particles and dried linseed oil.

 

I have the lack of a modeled experiment to approve these claims. I would need to apply cold-combined varnish on a well prepared wood and let it polymerize. After a bit of aging, SEM, SEM/EDX and FTIR needs to be done on my prepared samples. If they would match, this could support my theory. Until then this is not more than a humble theory.

 

I would enjoy any comment about this.

Michael

Thanks Michael, the plot thickens.

Application and rubbing by hands and fingers is what I do to speed things up and heat things up to about 80 degrees C. I can get a layer of linseed oil that dries hard qutie quickly and the final layer with rosin and oil that dries very hard. I would like to know what is happening in that final layer that makes it resistant to scratches by fingernails?

But I wonder if Stradivari used different techniques from the 1690s to later? I find it hard to believe he had just one method for 70 years.

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5 minutes ago, sospiri said:

That's a relief to know he won't be turning good instruments into screechboxes.

 

In my experience, neither the application of shellac as an original varnish, nor subsequent application, will automatically turn a violin into a screechbox. However, I have often wished that it was that simple. ;)

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Just now, David Burgess said:

In my experience, neither the application of shellac as an original varnish, nor subsequent application, will automatically turn a violin into a screechbox. However, I have often wished that it was that simple. ;)

If it's thick enough it will. Yer just not doing it wrong enough to find out.

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17 minutes ago, sospiri said:

Application and rubbing by hands and fingers is what I do to speed things up and heat things up to about 80 degrees C.

Rubbing with hands and fingers can certainly speed some things up. But wow! You can heat things up to 80 C (176 F) just by rubbing with your bare hands? Are you unmarried and available? :lol:

(Signed, Pathetically Desperate Dude.)

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