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darkening the violin wood


Peter White

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I was under the impression that Brandmair and company specifically looked for and only found trivial amounts of protein in their analysis of classical varnish films... not enough to suggest an intentional coat as part of a finishing system.

 

Is that wrong?

 

Ernie,

What was identified was the presence of amino acids...the markers for proteins.  These proteins are not specific to any source, intentional or unintentional.

Joe

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Thanks Joe:

 

Then as follow-up... was enough amino acid found in the varnishes tested to leave open the possibility of an intentional protein layer like casein?  (by intentional I mean for example not the residue of wiped off glue when purfling was installed)

 

E

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Thanks Joe:

 

Then as follow-up... was enough amino acid found in the varnishes tested to leave open the possibility of an intentional protein layer like casein?

 

E

 

Ernie,

The presence of amino acids is confirmed, though any object made by human hands is likely to test this way, given the sensitivity of the methods used.  The amount?  Hard to say.  I think the proof is in the seeing.  There is no denying the possibility of an intentional application of a protein based layer.  I have yet to see or concoct a protein based material that has the optical properties of the classic Cremonese Ground.

Joe

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This is an interesting thread. I wrote about casein and casein emissions in the early 1980's. Making casein with quick lime was probably the method used in classical times. Amonia was not freely available. It has the advantage (as a glue [i believe it is technically a cement]) of being more waterproof. With quick lime it creates better emmusions than ammonia/borax mixes and it emulsifies with a lot of things other than just varnish and resins. 

 

 

Casein has a longer working time than gelatin based glues and as such can be adjusted. It can be used in fairly cold conditions without gelling. In hot dry weather there is no need for constant fire in the workshop. When dry it is also resistant to oils and most common solvents, which is why it was used to join the wooden panels used by painters. 

 

Today we talk about the reversible nature of gelatin glues as being advantageous, but who wants a center joint to pop? And opening rib to table joints glued with casein is not as difficult as it sounds. It was not analyzed at the time, but I opened a del Gesu (ribs to back) in the 1980's that had never been opened. Under the blocks the holding glue was whitish and dry and did not react to water. 

 

 

 

 

Also if anyone has ever removed classical ribs from a corner block they will know that the usual methods for releasing animal glue do not work. This is especially difficult with cellos. It explains why, in the past, so many blocks were replaced when repairs to the ribs were done. 

 

 

I read your article about casein glue a long time ago.

 

Today we talk about the reversible nature of gelatin glues as being advantageous, but who wants a center joint to pop?

 

I don't want that but it happens during winter.

 

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Casein with 10% lime yields a prompt reaction on wood that has been exposed to the sun or to UV light. It gives the wood a lovely, perfectly even, inimitable honey color.

This reminded me of a wedge of Engelmann I sawed apart recently, reportedly soaked in pickling lime for a year. It is very apparent that the lime didn't soak thru to the interior of the wood, where it remained pasty white. The limed parts were a much more attractive golden color. After thermal processing, this variation almost completely disappeared, for whatever that's worth.

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To my knowledge, researchers have not yet analysed all the Italian violins and not even all those from Cremona. For the time being, there is no agreement on the subject because there is no universal technique for preparing and varnishing wood.

The Italian makers worked as we do, each on his own, trying to obtain the best outcome with one point in common: a color similar to that of the Cremonese violins. Several techniques are possible and yield comparable results.Casein is a sizing like any other and is certainly not a varnish. No researcher has given the recipe for Cremonese varnish, but this does not keep contemporary violin makers from varnishing their instruments successfully.

 

There are at least four techniques for preparing wood that are identifiable and perfectly valid. The technique using plaster of Paris explained by Roger Hargrave, i.e. the gesso technique, with or without glue, which has always been used by painters on wood and canvas; sizing with a linseed oil varnish containg 40% colophany; sizing with gelatine; sizing witih casein.

 

www.kreitpatrick.com

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Of course there is no way to analyse all violins from the Cremonese time, but none of the six Stradivarius put under the microscope by Echard and his team showed any significant amount of casein under the varnish, but linseed oil was found inside the wood (and it's a quick and easy way to seal wood). there is even no proof that the Cremonese makers were actually making their own varnish. they could have simply bought it for what we know.

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In the last decade there has been a tremendous amount of scientific research on classical Italian violin varnish, particularly on Stradivari's varnish methods. Two studies, done with most of the same equipment, come up with very different conclusions. Bruce Tai in the 2007 VSA papers and the recent Stradivari Varnish book by Grenier and others differ in the number of coats or layers Stradivari and other contemporary makers used.  I tend to agree with the very recent Stradivari Varnish book that says there were probably four steps in Strad's varnish method: sealing, staining (darkening), one clear coat and one color coat. But I have some questions about this, provoked in part by Mr. Hargrave's use of rabbit urine and UV light, about the science and about a reasonable method of varnishing with resin and linseed oil.

(1) were there 2 coats of varnish or 11 coats, the conflict raised by the two studies mentioned above

(2) If Strad used multiple coats of resin and linseed oil varnish, how did he have time to sun dry somewhere around 1300 instruments in cloudy and rainey Cremona ?

(3) If he used only two coats as suggested by Stradivari Varnish, do you makers really think that one color coat of vermillion colored varnish would produce a vibrant red violin on white wood?

(4) Therefore Strad had to have darkened the wood to produce the flame, the color, and quantity of violins he made.

(5) Does anyone have a reasonable (scientific or practical) method of darkening the wood before varnishing?

I appreciate all the work that has gone into these studies, and the practical value of Mr. Hargrave's use of urine and UV, but no one as far as I know can determine how Stradivari darkened his wood--chemicals, dyes, stains, urine? I have 35 years of experience with resin and linseed oil varnish, and I fail to see how two coats of this varnish could produce anything like a classical finish, unless (a) the wood was darkened considerably first and ( B) the color agent was very powerful in intensity and other characteristics.

One of the reaasons I raise these questions is because multiple coats of linseed oil varnish will reduce volume and tone, additionally it is too time consuming, Glazing is not the answer. So, interestingly, the so-called "secret" to Strad's varnish is that there was very little varnish!!!

Help me out on this one makers, please.  Thanks. Peter White

Hi Peter- Appreciate it if you expand your statement of "linseed oil and resin".  There are many resins, processed differently.  Thanks 

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What was identified was the presence of amino acids...the markers for proteins.  These proteins are not specific to any source, intentional or unintentional.

Hi Joe,

 

If I recall correctly, Brandmair did mention specific proteins (casein, collagen and ovalbumin) with respect to at least two samples.

 

John

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Of course there is no way to analyse all violins from the Cremonese time, but none of the six Stradivarius put under the microscope by Echard and his team showed any significant amount of casein under the varnish, but linseed oil was found inside the wood (and it's a quick and easy way to seal wood). there is even no proof that the Cremonese makers were actually making their own varnish. they could have simply bought it for what we know.

 

In the 2009 communication “The Nature of the Extraordinary Finish of Stradivari's Instruments”, Echard and his team mention being able to rule out protein materials such as egg, casein, or animal glue as significant components of the underlayer.  However, within the earlier 2008 publication “Quelques résultats d'analyses chimiques sur des vernis d'instruments d'Antonio Stradivari”, Echard and fellow author Stéphane Vaiedelich make specific mention of the possible presence of a protein underlayer in relation to the Davidoff Strad and the head of the viola d'amore.

This is one of several earlier findings that have either changed or not been mentioned in the 2009 communication.

It would be nice to know more....

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John,

When I spoke directly to M. Brandmair her words were "we found the presence of amino acids".   As a scientist she would not speculate further.

When JP Echard did his tests he set out to find, define, and quantify the "mineral ground" once and for all.  When his testing methods did not show this "layer" he assumed he made a mistake and did the analysis all over again...only to reach the same conclusion. 

on we go,

Joe

 

Lest I be known as having a narrow approach....I'll clarify.  There are MANY good ways to prepare the instrument for varnishing...ie. "grounds".  Varnishing over a darkened wood preparation...or a gesso filled surface...or shellac....casein emulsions...or any of the commonly successful methods can [and will under the right hands] produce a fine finish.  If we are speaking directly of the best of the Cremonese grounds ... or are trying to reproduce this effect, then that is a different set of criteria....

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When I spoke directly to M. Brandmair her words were "we found the presence of amino acids".   As a scientist she would not speculate further.

When JP Echard did his tests he set out to find, define, and quantify the "mineral ground" once and for all.  When his testing methods did not show this "layer" he assumed he made a mistake and did the analysis all over again...only to reach the same conclusion. 

 

Hi Joe,

 

Thank you for your reply and comments.

 

My notes taken while reading Brandmair's section in “Stradivari Varnish” mention the following:

1. Advanced analyses via indirect ELISA on microsample 1730/5 which contains wood confirmed a small amount of casein.

2. Re sample 1720/3, via ELISA found various proteins – tests for collagen as well as ovalbumin were positive in this sample. Further collagen tests considering fish and sturgeon were negative, etc..

3. Re Strad cello wood sample 1707, ELISA definitely positive for collagen (in general) and negative for all other tested proteins. Fish and sturgeon can also be excluded. GC/MS confirmed ELISA analysis.

4. Re old Italian cello 17??, probably Strad, indirect ELISA found two different proteins; i.e., ovalbumin and collagen. GC/MS confirmed collagen.

 

I must emphasize that these are my notes and will not reflect the exact wording that appears in the book. I can dig out the book and check (and it will take some digging in my workshop!) but I am positive that the mention of specific proteins will have resulted from what actually appears in the book.

 

My posting in response to Robertdo's post #84 was focused on Echard and his teams' findings relating to the presence or not of proteins. The controversy surrounding the presence or not of any mineral ground is a separate issue again.

 

I hope that this makes sense.

 

John

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It is mainly linseed oil (in variable quantities) that is added to the casein emulsion; it can thus be identified on the wood's surface. Casein does not penetrate the wood at all: it forms an extremely thin layer on the surface. A colophane varnish sizing should not penetrate the wood, either. 

 

Store-bought casein must not be confused with the home-made variety: it is not at all the same!  Once pigments have been added to commercial casein to obtain the desired color, it is used for painting walls or furniture.

 

www.kreitpatrick.com

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For me, more "interesting" than the results of chemical or immunological analysis, is the absence of any layer between wood and varnish as Echard was able to show simply using microscopy. Even if the paper only shows one picture of the top, he states in the paper that the result was the same on the tops and backs of each violin. And on this picture we see the wood cells filled with linseed oil and just above a varnish layer. Given the scale of the picture it's awfuly difficult to imagine a layer of casein or any other protein sealant that would be less than 5 microns thick.

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I don't know about the scientific analysis, but I do not agree with this phrase.

 

It is like saying that if it were not for the color and consistency of their paints, Leonardo or Michelangelo could never have achieved greatness.

 

The little I know, is that only after I've learned about materials I realized why I liked so much these and other old masters, and many modern artists who paint well can not come close to them - the materials. One material without being applied is a work of art by itself, the other tube color, just a mediocre thing, not a gem, it tints but...no magic...nice, but no cigar...

 

Maybe history written by Spike Bucklow can say it better than me....

 

....Compared with most other pigments, the lowest grade of azurite was expensive, and the best grade cost four times as much as the worst. Around 1500, Albrecht Dürer, the great German artist, bought ultramarine at ten times the cost of the best azurite. As a result of its expense, ultramarine was often specifically mentioned in artist’s contracts...

 

...Ultramarine was probably more expensive in Germany than in Italy because most came into Europe through Venice. Nonetheless, Italian painters also treated ultramarine as special and it was commonly mentioned in their contracts as well. For example, in 1408, the contract commissioning a now lost cycle of frescos by Gherardo Starnina stated that ultramarine for the Virgin should cost two florins per ounce. The ultramarine used elsewhere in the same cycle was a lower grade, costing only one florin per ounce....

 

...For example, the 1320 contract for an altarpiece in Santa Maria della Pieve, Arezzo, required Pietro Lorenzetti to use the best gold of one hundred leaves to the florin....

 

Excerpt from - The Alchemy of Paint

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John,

If memory serves me you are correct in your information from the Brandmair study.  Even on the samples where a particular protein was found, she would not classify the finding as intentional.  As we know, not every Stradivari instrument is the same...ground included.  As a protein sealer is quick and easy, it seems logical that instruments that need to get done fast were treated in a different way.

 

Attached are pictures of the back of the original fingerboard from the Stradivari Lady Blunt [1721].  The first photo was taken in late afternoon indirect natural light.  The second photo has added high intensity incandescent lightNote the color of the leather desk top it sits on.

 

Joe

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Has anybody ever tried to find out why on quite a few Cremonese instruments (not exclusively), the wood turns almost red on worn parts like the scroll or shoulder?

Is there a substance or chemical reaction that turns wood red when exposed to maybe sweat?

I have in mind instruments like the Amaties in the Ashmolean museum, under the varsish golden brown but quite red and without dirt in other places.

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Mr. Kreit:  Your description of casein and how colors may be added or produced is a very helpful piece of information. This gives me something to take to the chemists to work with because,  from what I understand you have said,  this does not contradict the findings in the Stradivari Varnish book. This is very interesting information.  Can you tell us a little bit more about your experience with Casein and color?  I assume you use this as your sealer/primer layer and that it works very well for you.

There is a lot of information in your post and I want to try the various combinations.  Thanks for this.  Tell us a little more about the process following the sealer/primer if you will.  Peter

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John,

If memory serves me you are correct in your information from the Brandmair study.  Even on the samples where a particular protein was found, she would not classify the finding as intentional.  As we know, not every Stradivari instrument is the same...ground included.  As a protein sealer is quick and easy, it seems logical that instruments that need to get done fast were treated in a different way.

 

Attached are pictures of the back of the original fingerboard from the Stradivari Lady Blunt [1721].  The first photo was taken in late afternoon indirect natural light.  The second photo has added high intensity incandescent lightNote the color of the leather desk top it sits on.

 

Joe

 

Hi Joe,

 

These are very interesting photos!  Thank you for posting them!!

As you mention, not every Strad is the same.  In fact the more I see the more I become aware of differences.  And then there is the effect that different lighting has.  The appearance of Strad varnish and ground certainly seems to change very significantly under different lighting and changes in light direction. 

 

On the topic of ground appearance, I wonder whether much of the change between instruments is merely due to how his ground system reacted with each piece of wood.  Having tried many and varied ground systems, it seems that wood difference is one of the major factors, if not the major factor, in not being able to get a consistent appearance from one instrument to the next.

 

I am not sure that I understand your sentence "Even on the samples where a particular protein was found, she would not classify the finding as intentional."  Could you please expland on this?

 

Many thanks.

 

John

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