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Michael Szyper

Stradivari Varnish oil/resin ratio

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There is a reality to varnish making that is not realized in this discussion.  When you make a 1:1 or 1:1.5 resin:oil varnish, the varnish is extremely thick (almost solid) when the cooking is finished and allowed to cool down.  You have to add turpentine to it to have any chance of ever coating the instrument.  The amount of turpentine will determine how brushable the varnish will be.   You do not need to add uncooked oil for this.  Note, during the varnish making step, the oil chemically reacts with the rosin--that is why it is cooked.

Personally, I add the thinned varnish to pumice for the initial coat--this is tantamount to using a thick varnish.  This is so thick that it is rubbed on.  You do not need a special varnish recipe for this.

For Mr. Cowboy:  I do not have the B & G book.  According to those that have read it, the 4:1 ratio is for the  varnish adjacent to  the wood.  So, the components have  already been fully reacted (cooked) when turned into a varnish and the wood was coated.

The chemistry of the varnish is a mystery for me.  The process starts with the cooking meaning that some polymerization takes place during the cooking chemical reaction.  This is later completed when the varnish is applied to the wood and additional polymerization takes place to set the film.  It is a mystery how a scientist can analyze the film years later and then determine the resin:oil ratio.  I am going to look at the Echard papers again.

Mike D

 

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1 hour ago, Bodacious Cowboy said:

My boggled mind was thinking about an 80:20 mix of colophony and oil. So essentially 80% processed resin with all the volatiles driven off, and solid at room temperature. This would contrast to using unprocessed pine resin, or venice/strasbourg turpentine as the resin, which would be usable as a varnish in an 80:20 mix. But in this scenario, the resin/oil  weight ratio wouldn't be 80:20 after cooking, when all the volatiles had been driven off from the resin, would it? This is what confuses me about the Brandmair results. Are they saying that the varnish had an 80:20 weight ratio on application? In which case, surely some solvent must have been used? I confess I don't have the book. Also, I don't expect Joe to reply if it would involve revealing or hinting at any commercially sensitive info.

Sorry if this seems like the babbling of an incoherent mind.

This sounds like my thinking as I did the research on this varnish.  However it is possible!

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1 hour ago, Bodacious Cowboy said:

My boggled mind was thinking about an 80:20 mix of colophony and oil. So essentially 80% processed resin with all the volatiles driven off, and solid at room temperature. This would contrast to using unprocessed pine resin, or venice/strasbourg turpentine as the resin, which would be usable as a varnish in an 80:20 mix. But in this scenario, the resin/oil  weight ratio wouldn't be 80:20 after cooking, when all the volatiles had been driven off from the resin, would it? This is what confuses me about the Brandmair results. Are they saying that the varnish had an 80:20 weight ratio on application? In which case, surely some solvent must have been used? I confess I don't have the book. Also, I don't expect Joe to reply if it would involve revealing or hinting at any commercially sensitive info.

Sorry if this seems like the babbling of an incoherent mind.

This sounds like my thinking as I did the research on this varnish.  However it is possible!

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1 hour ago, Mike_Danielson said:

 I do not have the B & G book.  According to those that have read it, the 4:1 ratio is for the  varnish adjacent to  the wood.  So, the components have  already been fully reacted (cooked) when turned into a varnish and the wood was coated.

I have the book, and she says the ratio is the same for all layers of varnish, both ground and colored.

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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. 

If the methodology and explanation in the B/G book is correct, it states that 80:20 is the ratio of the final, dried product. I made several 80:20 varnishes using heavily cooked rosin, and it definitely is possible to use this kind of ratio.

The more I compare B/G, Echard and Barlow/Woodhous, the more I think that all their scientific results are correct and the huge differences in the Interpretation are not based on the completely different qualities of the examined varnish but just on the Interpretation of the result. 

I will try to post an overview with citations of the articles and try to bring the different interpretations together in the way I would interpret it.

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11 minutes ago, Michael Szyper said:

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. 

We need to be careful here:  is the 80:20 ratio (also the same as  4:1)  oil:resin or resin: oil?  In other words, is the resin the major component?

Mike D

 

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23 minutes ago, Mike_Danielson said:

 

Yes, clearly: 80% per weight of heavily cooked Rosin, (weight after cooking), and 20% per weight of cooked oil. Rosin is the major ingredient. 

 

21 minutes ago, Bodacious Cowboy said:

Thinned with solvent?

yes sir.

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6 minutes ago, Michael Szyper said:

Yes, clearly: 80% per weight of heavily cooked Rosin, (weight after cooking), and 20% per weight of cooked oil. Rosin is the major ingredient. 

 

yes sir.

Thank you. You may call me Bo.

I think I'll have to stop being a tightwad and buy this book.

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1 hour ago, Michael Szyper said:

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. 

If the methodology and explanation in the B/G book is correct, it states that 80:20 is the ratio of the final, dried product. I made several 80:20 varnishes using heavily cooked rosin, and it definitely is possible to use this kind of ratio.

The more I compare B/G, Echard and Barlow/Woodhous, the more I think that all their scientific results are correct and the huge differences in the Interpretation are not based on the completely different qualities of the examined varnish but just on the Interpretation of the result. 

I will try to post an overview with citations of the articles and try to bring the different interpretations together in the way I would interpret it.

I will have to go back and check  , but if I remember correctly the Greiner varnish was cold solved not cooked. 

The book is worth twice the price.   Order from Brandmair's web page, she makes more that way.

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31 minutes ago, joerobson said:

Greiner varnish was cold solved not cooked

I am not sure about that, have to check it. There are reasons to assume that Strad did also cold mix his varnish. As I said before, I want to explain my point a bit more in detail...

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8 minutes ago, Michael Szyper said:

I am not sure about that, have to check it. There are reasons to assume that Strad did also cold mix his varnish. As I said before, I want to explain my point a bit more in detail...

I look forward to your post once you have collected your thoughts. As to cold solving varnish, I don't understand the benefits or why it would be thought of as likely, given the lengthy documented history of cooking resins into oil.

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The determination of the rosin:oil ratio is on p. 140 f.19 of B&G. 

My reading says the cooking was done at 120C which seems low to most varnish makers. However, for FTIR analysis this cooking temperature won't change results - so I am told.

Anyhow the 4:1 ratio works for me. It wears the right way (easily) and looks right under UV. 

 

 

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1 hour ago, Melvin Goldsmith said:

I find that varnishes with a high resin content show characteristic white scratches that one does not find in old Cremonese work. 

I'm sure that this much cooked/reduced resin 120g -> 65g wouldn't work with 4:1 resin/oil ratio. It wouldn't come out of the jar without 50-60g of turp and would be sticky and brittle.

https://photos.google.com/share/AF1QipPJvUiUh15aPWjeOKee0ChZoikX24KvaswapdIjrSXoBK4GNzyDLu6aRTC8O1o6pA?key=M0pNRC1xWFcyc19MOF9YeEgtN3VlRGVQSGNNbmtB 

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10 minutes ago, Strad O Various Jr. said:

Shellac from "restorers" not there originally!! That's why they all look so shiny.

But now part of the varnish. So the question arises: what do we like to imitate? An original varnish "idea" that practically no longer exists on instruments, or the "composite" varnish that is currently found on instruments and interacts with them?

Providing that imitating is our aim...:)

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17 hours ago, JacksonMaberry said:

I look forward to your post once you have collected your thoughts. As to cold solving varnish, I don't understand the benefits or why it would be thought of as likely, given the lengthy documented history of cooking resins into oil.

Me too.

The benefits are: it's easy and quick to do, it can dry very hard and it's possible to control the tonal effects.

 

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5 minutes ago, Strad O Various Jr. said:

Shellac is not good for tone, I heard a Strad that had been somewhat ruined by about 15 coats of shellac.

And how were you able to differentiate the affect of the “15 coats of shellac” from a myriad of other possible contributing factors?

One of the best sounding violins I know is varnished almost entirely with shellac...

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2 minutes ago, Mark Norfleet said:

And how were you able to differentiate the affect of the “15 coats of shellac” from a myriad of other possible contributing factors?

One of the best sounding violins I know is varnished almost entirely with shellac...

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.

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