Stradivari Varnish oil/resin ratio


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2 hours ago, Bill Yacey said:

That's an issue I've had in trying to understand these varnish recipes; as the resin cooks, the weight or volume changes considerably according to the time it's cooked, and the temperature.

Perhaps the best way would be to precook the resin, let it cool, crush it, document the weight, and then re-heat it only hot enough to combine with the oil. This would give a better indication of the true resin / oil ratio.

 

2 hours ago, Bill Yacey said:

I've seen some descriptions that indicate long cook times after combining the resin and oil; this cooking time could certainly cast considerable doubt into what the final product actually is.

I weigh the hot resin while I cook/reduce it, so I know what weight ratio oil to add. It doesn't matter if you let it cool and re heat it when combining it with oil.

But longer cooked resin needs more oil to resin weight ratio. For my 10+ hour cook it seems to be good when 1:1. For shorter resin  cook it gets too "oily" if the weigh ratio is 1:1 and as Joe said difficult to polish.

It also gets more difficult to polish if you add drops of oil when varnishing. It's a fine balance and I don't think that just giving the ratio would help anybody, you also need to learn the particular ingredients you are using. All resin and oil are not equal, they vary a lot. It's actually a skill you get better at for every cook.

 

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Echards paper on the layers is an interesting one. Sometimes it seems to me like every scientist gets different results in exactly the same topic, almost like in medicine :)

I have to check the graphs against the Brandmair’s and see wether the different results are really due to the results or rather because of their different interpretation.

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2 hours ago, David Burgess said:

Huh? What the heck does "sweat" mean? Oil which wasn't sufficiently dried, or wasn't sufficiently combined with the resin, so it leached out to the surface? Or are you talking about the way moisture condenses on a cool surface, like on a glass of ice-water, or on cool blades of grass overnight?

 

sorry David...varnish making term...the varnish will get hazy in humid weather or radical temperature changes.

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3 hours ago, 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 · 6 downloads

Thanks for posting this, I had not read it. If I understand correctly, this study concluded that the ground is strictly linseed oil and that the varnish was a colophony varnish with pigments mulled in, applied in a single coat. Talk about "keeping it simple"!

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Regarding Echard's contribution to this discussion, more recent relevant material can be sourced here: https://www.researchgate.net/profile/Sophie_Tirat

Also worth considering, particularly pages 140-149, is this: https://tel.archives-ouvertes.fr/tel-00742851/document

Adding more, Echard has mentioned issues associated with the detection of certain resins, e.g., amber, which, as far as I know, he has not expanded upon.  On this point, note White's comment regarding the detection of amber.  Similar issues appear to apply to other run resins and possibly triterpenoid resins within certain aged varnish systems.

It seems that the jury is still out...... 

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My understanding about the B&G 4:1 is that it was arrived at as a result of experiments Greiner did with various batches of varnish he made.  It's also worth keeping in mind the resin being used will give different results, Greiner was using rosin oil and resin, not pure spruce resin as Brandmair suggested was most plausible.  Taking Greiner out of the equation because of the possibility of preformed maker's bias, Brandmair and Echard agree a lot more closely than it might seem on first glance.  Especially taking into account other analysis by Brandmair, I don't think she ever rules out the possibility of an oil ground.  My two cents.

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8 hours ago, Jim Bress said:

This is the first time I'm hearing about adjusting the varnish for cello compared to violin (or viola). In what way are they different?  Something a little more flexible because of additional wood movement, or something completely different?

-Jim

Jim,

I think this is most likely because you need a longer "open time" on a cello to allow for applying an even coating before it starts to dry. I tend to thin the varnish with terps or essential oils more than I would on a violin. What Strad actually did or even what Rene was really seeing in the finished film I really don't know. But he did state to me that they were different as if that was an accepted fact.

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8 hours ago, Davide Sora said:

It also seems to me that there is a difference, but only in the thickness (greater for the cello)

 

30 minutes ago, nathan slobodkin said:

Jim,

I think this is most likely because you need a longer "open time" on a cello to allow for applying an even coating before it starts to dry. I tend to thin the varnish with terps or essential oils more than I would on a violin. What Strad actually did or even what Rene was really seeing in the finished film I really don't know. But he did state to me that they were different as if that was an accepted fact.

Good food for thought.  Thank you gentlemen.

-Jim

 

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12 hours ago, nathan slobodkin said:

Morel told me he thought the varnishes on Strad cellos were different than on the violins

Definitely. 

From simple observation Strad cellos have a somewhat thicker and in comparison to his violins a more opaque varnish.

I am inclined to think that the color agent used for violins was too expensive so he would use a cheaper coloring agent, maybe pigments.

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On August 3, 2020 at 10:22 PM, Michael Szyper said:

Share your latest thoughts about this topic. I would like to split it up into different disciplines:

1. Science: B&G 80% resin VS Prof. White’s lower resin contents

2. Trial and error: I made and used plenty of low oil varnishes around 4:1 res./oil with success. Not having scraped along a Strad Varnish I still don’t believe that it is that brittle on the surface. What are your experiences?

It makes me wonder how precise GC/MS et al is regarding resin/oil contents. The Jaegers Lab, for example, could not reveal the exact resin content in Koen’s varnishes. Since they are a highly respected lab, I doubt that it was due to the lack of skill or experience.

 

 Any thoughts?

Just my personal viewpoint:

I was never a fan of varnishes with high oil content and I think 20 percent is somewhat the maximum IMO. However this somehow contradicts existing oil varnish recipes from the old times where you mostly find more than 50 percent and up to 2/3 oil.

I tried to reproduce such recipes but probably I am simply not experienced enough to make them work. (I always ended up with a sort of sticky sauce)

The Koen Padding varnish is something different from most oil varnishes because there is no Turpentine thinner in it. Accordingly the linseed oil content must be high enough to make the varnish flow. But at the same time it would not be too liquid because it is applied with using hand and fingers.

For scientific research I got a little bit uneasy about 'bullet proof' findings. Barlow Woodhouse reported in their paper the use of minerals and then 20 years later other researchers (I think Brandmaier as well as Echard et al.) are saying they found no minerals only linseed oil. 

The only explanation I can find is that MAYBE the old makers had a different treatment for the spruce top than the rest of the instrument.

In any case I looked in vain on the research papers for a statement where the examined varnish probes were taken or if this was not necessary which portion of the instrument was examined. 

In the end I believe that every maker should confront with scientific findings and emulate from there his own best practices. The idea to reproduce exactly what Stradivari did is most likely impossible because there is a good chance that he didn't always use the same varnishes (provided by Cremonas alchemist) and additives to the varnish. 

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I reviewed the Infrared spectra of the Echard paper. The ground layer has a pretty weak OH shoulder and a narrow C-O band. I can’t disagree about the conclusion that this measurement may belong to linseed oil or a very fatty varnish. But I could imagine that a heavily limed resin varnish could have a similar IR spectrum to the linseed oil. Any thoughts?

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10 hours ago, Advocatus Diaboli said:

My understanding about the B&G 4:1 is that it was arrived at as a result of experiments Greiner did with various batches of varnish he made.  It's also worth keeping in mind the resin being used will give different results, Greiner was using rosin oil and resin, not pure spruce resin as Brandmair suggested was most plausible.  Taking Greiner out of the equation because of the possibility of preformed maker's bias, Brandmair and Echard agree a lot more closely than it might seem on first glance.  Especially taking into account other analysis by Brandmair, I don't think she ever rules out the possibility of an oil ground.  My two cents.

Whoever said that Stradivari consistently repeated a standard method? I’m serious about this. 

IMO, Greiner may  be a master luthier, but his training biased his conclusions.  Brandmair is the scientist. 

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If you read the Nagyvary review of the B & G book, you find that it was never submitted to a peer review before being published.  This is a serious problem with the B&G book.  So, I do not take it very seriously.

I am going to go with Occam's Razor when looking at the famous Strad varnish.  What ever varnish was used adjacent to the maple wood is probably the same stuff used above the wood; why have two varnishes around the shop.

We all know from personal experience that the spruce must be sealed with something.  Occam's razor again--every shop had a glue pot.  Glue was probably used on the spruce as well, but probably not as many coates (my surmise).

The inconsistency between the Echard results and the Woodhouse results with regard to the mineral layer has never been explained.  How about this for a wild idea--all the instruments Echard examined are copies by master forgers.

Mike D

I edited this to change White to Woodhouse--my error.  This inconsistency between Echard and Woodhouse is a big deal

 

 

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19 hours ago, Mike_Danielson said:

The inconsistency between the Echard results and the White results with regard to the mineral layer has never been explained.  How about this for a wild idea--all the instruments Echard examined are copies by master forgers.

Mike D

 

 

That is quite simply not true.  Also it is worth noting that the Dr. White study did not include a Stradivari instrument.

Joe

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On 8/4/2020 at 9:43 AM, sospiri said:

 Also my own 80% oil 20% rosin cold application coats are extremely polishable, I can assure you of that fact. 

What kind of oil did you use?  If you have put the cold application on a violin yet did it sink down into the spruce when applied?

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Amorphous mineral particles can be invisible in vis-microscopy. Barlow and Woodhouse were the only so far to use an electron microscope. It is the best method IMO for detecting particulate layers and it should be done on the instruments of the cite de musique, just to compare the sensitivity of the measuring techniques.

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On 8/5/2020 at 2:49 PM, Mike_Danielson said:

 

The inconsistency between the Echard results and the Woodhouse results with regard to the mineral layer has never been explained.  How about this for a wild idea--all the instruments Echard examined are copies by master forgers.

 

9 hours ago, joerobson said:

That is quite simply not true. 

Joe, please state your reasoning behind your conclusion.

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4 hours ago, Michael Szyper said:

Amorphous mineral particles can be invisible in vis-microscopy. Barlow and Woodhouse were the only so far to use an electron microscope. It is the best method IMO for detecting particulate layers and it should be done on the instruments of the cite de musique, just to compare the sensitivity of the measuring techniques.

Echard has employed electron microscope in his studies.  See p.108 onwards in his Ph.D. thesis. 

It also seems that Brandmair employed SEM/EDX.  This is listed in her summaries of analytical results for the various samples considered in her section of Stradivari Varnish.  She also mentions it being used for the mapping of inorganic compounds.

Edited by John Harte
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