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Michael Szyper

Stradivari Varnish oil/resin ratio

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9 hours ago, Mike_Danielson said:

The EDAX data proves this to be the case. 

How can you prove that a layer consists mainly of substance x and not substance y if a method (EDX) is only capable of detecting substance x?

As I mentioned, what I wrote is only an interpretation - i.e. the same what Barlow did with his data. I would like to discuss the methods used in those papers and mainly their weaknesses, because only then we can interpret the data in a better way. I just find it intriguing that the data provided by the publications is not all that different, but the interpretations does.

I agree with you that FTIR alone is not sufficient to provide exact resin:oil ratios. Brandmair wrote that the FTIR spectra compared best in the case of 80:20 varnishes. This does not necessarily mean it is definitely a 80:20 mix. 

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Let me add this. Stradivari did vary his varnish system over time. The biggest change was around 1696 when he moved from an Amati system to his own that appears on his Golden Period instruments. I believe that there is evidence for another change after ~1730. Moreover, there are subtle variations even during the Gold Period. My own experiments show that methods of making varnish/ground and their application to wood also produce variations. This is why I advocate having one Stradivari violin available for testing by all the major researchers. That would reduce the noise.

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1 hour ago, sospiri said:

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

I don't see any reason why shellac applications would be thick or thicker, compared to an oil varnish application.

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13 minutes ago, Wood Butcher said:

I don't see any reason why shellac applications would be thick or thicker, compared to an oil varnish application.

Nor do I. Myths have a life of their own.

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4 hours ago, Michael Szyper said:

How can you prove that a layer consists mainly of substance x and not substance y if a method (EDX) is only capable of detecting substance x?

As I mentioned, what I wrote is only an interpretation - i.e. the same what Barlow did with his data. I would like to discuss the methods used in those papers and mainly their weaknesses, because only then we can interpret the data in a better way. I just find it intriguing that the data provided by the publications is not all that different, but the interpretations does.

I agree with you that FTIR alone is not sufficient to provide exact resin:oil ratios. Brandmair wrote that the FTIR spectra compared best in the case of 80:20 varnishes. This does not necessarily mean it is definitely a 80:20 mix. 

Michael, in my August 5 post mention was made of a couple of sources associated with Echard that consider resin to oil ratio.  Celine Daher's thesis is particularly interesting with respect to resin to oil ratio.

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31 minutes ago, John Harte said:

Michael, in my August 5 post mention was made of a couple of sources associated with Echard that consider resin to oil ratio.  Celine Daher's thesis is particularly interesting with respect to resin to oil ratio.

My French isn't great and I was scanning quickly, but one "takeaway" I got from the thesis was that the spectra of resins change as a result of ageing. Maybe something to bear in mind given that some of the conclusions in the Strad varnish book (as I seem to recall someone mentioning above) are based on comparing spectra between original and freshly prepared varnish. Or maybe not. :)

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3 hours ago, Bodacious Cowboy said:

My French isn't great and I was scanning quickly, but one "takeaway" I got from the thesis was that the spectra of resins change as a result of ageing. Maybe something to bear in mind given that some of the conclusions in the Strad varnish book (as I seem to recall someone mentioning above) are based on comparing spectra between original and freshly prepared varnish. Or maybe not. :)

My French isn't great either but there are some reasonable online translators that can transform one's understanding. :)

Another takeaway - If you read the section on the Provigny (pp.147-148) you will see some interesting data on resin/oil proportions.

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10 hours ago, John Harte said:

My French isn't great either but there are some reasonable online translators that can transform one's understanding. :)

Another takeaway - If you read the section on the Provigny (pp.147-148) you will see some interesting data on resin/oil proportions.

Thank you, John. I hadn't read that far when I posted earlier.

The resin/oil ratio in the Provigny surface varnish is measured in these experiments to be 40/60? Am I interpreting this right?

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10 hours ago, Bodacious Cowboy said:

Thank you, John. I hadn't read that far when I posted earlier.

The resin/oil ratio in the Provigny surface varnish is measured in these experiments to be 40/60? Am I interpreting this right?

Yes.  The ratio for the sub-layer is also interesting which may beg some questions, or may not....

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If you consider that the oil and the resin separate over time in a cold brew, it's also likely that the ratio changed...

I find this very interesting btw. 

On another subject I'm still puzzled by BB finding a protein layer and Echard not... 

I you test my instruments you will also find it on some, on others not, on some only on the spruce, but they both seem to get consistent result, just different ones.

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14 hours ago, pbelin said:

On another subject I'm still puzzled by BB finding a protein layer and Echard not... 

I you test my instruments you will also find it on some, on others not, on some only on the spruce, but they both seem to get consistent result, just different ones.

I suspect that there might be more agreement than we might imagine... Echard has found protein presence in Strad varnish systems but not in the form of a discrete protein layer as a hide glue size might form.  BB has found protein presence in upper wood cell structure of Strad sample material.  It is interesting to note that this also does not appear to be in the form of a discrete protein layer as a hide glue size might form. 

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On 8/4/2020 at 7:44 PM, Davide Sora said:

 

In fact, Echard interpreted what he found in the wood (with a penetration from 30 to 100 micrometers in the maple and from 10 to 30 micrometers in the spruce) as a drying oil, with no added particulates.

Echard-Stradivari finish.pdf 402.73 kB · 31 downloads

Echard's works on violin varnishes are scientifically among the best I have seen. There are two more I know of. But he never bother to quantify the oil/rosin ratio. Figure 4 in the Angewandthe paper sheds light on this, but peak intensities in GCMS are not particularly quantitative without proper calibration. Nevertheless, if you add all the peaks marked with a round dot vs the P, O and S it looks like a oil/resin ratio of 3/2.

It is however possible that his GCMS only measures the unpolymerised parts of resin and drying oil. If drying leads to cross-linked products they would not show up.

 

 

Echard 2004.pdf Echard 2007.pdf

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21 minutes ago, Strad O Various Jr. said:

I don't think an oil/resin ratio of 3/2 is a practical varnish, seems to me it would never dry.

What on earth gives you that impression, when properly processed linseed oil will dry completely on its own?

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25 minutes ago, Strad O Various Jr. said:

I don't think an oil/resin ratio of 3/2 is a practical varnish, seems to me it would never dry.

Oil without any resin at all will dry just fine, and will even eventually become hard and brittle, given enough time, or if exposed to enough sun or UV.

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On 8/13/2020 at 5:15 PM, Wood Butcher said:

I don't see any reason why shellac applications would be thick or thicker, compared to an oil varnish application.

 

On 8/13/2020 at 5:30 PM, David Burgess said:

Nor do I. Myths have a life of their own.

What myth are you refering to?

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On 8/16/2020 at 2:38 AM, John Harte said:

I suspect that there might be more agreement than we might imagine... Echard has found protein presence in Strad varnish systems but not in the form of a discrete protein layer as a hide glue size might form.  BB has found protein presence in upper wood cell structure of Strad sample material.  It is interesting to note that this also does not appear to be in the form of a discrete protein layer as a hide glue size might form. 

John, could it be from skin cells? I'm sure that there must be some keratin in my oil grounds from rubbing.

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On 8/15/2020 at 9:38 PM, John Harte said:

I suspect that there might be more agreement than we might imagine... Echard has found protein presence in Strad varnish systems but not in the form of a discrete protein layer as a hide glue size might form.  BB has found protein presence in upper wood cell structure of Strad sample material.  It is interesting to note that this also does not appear to be in the form of a discrete protein layer as a hide glue size might form. 

 

1 hour ago, sospiri said:

John, could it be from skin cells? I'm sure that there must be some keratin in my oil grounds from rubbing.

When these studies were published I inquired into the results in industrial settings not related to the violin world.

These are incredibly sensitive tests.  Both sources confirmed the validity of the tests.   Both said that the most likely explanation was that the instruments were made by human hands.

on we go,

Joe

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