Stradivari Varnish oil/resin ratio

[Michael Szyper]

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?

[Bodacious Cowboy]

2 hours ago, 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?

Who's Prof White? (in the study with the lead pipe)? 

Poor joke, sorry, but haven't heard of this work. My bad, probably.

[Michael Szyper]

I don’t remember his study, but mr. Hargrave mentioned his work in the bass book. I think Koen also mentioned him some article. 

[Bodacious Cowboy]

OK, found some stuff. Raymond White, UK National Gallery.

Can't find the study where he determines Strad varnish composition, though...

[Davide Sora]

4 hours ago, Bodacious Cowboy said:

OK, found some stuff. Raymond White, UK National Gallery.

Can't find the study where he determines Strad varnish composition, though...

I only know these two articles from The Strad, which I think summarize R. White's research on varnish.

White article - Strad Aug 1984.pdf

White article Oct 1984.pdf

[Bodacious Cowboy]

Grazie, Davide.

[Violadamore]

6 hours ago, Davide Sora said:

I only know these two articles from The Strad, which I think summarize R. White's research on varnish.

White article - Strad Aug 1984.pdf 2.5 MB · 7 downloads

White article Oct 1984.pdf 1.12 MB · 7 downloads

Thanks much!!

[Michael Szyper]

Great read, thanks Davide

[joerobson]

I have discussed this with both M. Brandmair and JP Echard.  The scientific analysis is lacking.   Observation however gives us more information.   The varnish which is in first contact with the wood seems likely to be 4 resin to 1 oil.  However the making of that varnish retains flexability.  A very short oil varnish would be far more brittle than we observe and would make varnishing a cello very difficult.

In varnish maker's terms a varnish of 1:1 is the most oil a varnish can hold and still be considered polishable.

Joe

[sospiri]

53 minutes ago, joerobson said:

I have discussed this with both M. Brandmair and JP Echard.  The scientific analysis is lacking.   Observation however gives us more information.   The varnish which is in first contact with the wood seems likely to be 4 resin to 1 oil.  However the making of that varnish retains flexability.  A very short oil varnish would be far more brittle than we observe and would make varnishing a cello very difficult.

In varnish maker's terms a varnish of 1:1 is the most oil a varnish can hold and still be considered polishable.

Joe

But Echard says the rosin/oil layer is not in contact with the wood, only the oil layer and the rosin/oil layer that sits on top of that.

 Also my own 80% oil 20% rosin cold application coats are extremely polishable, I can assure you of that fact. Just because you insist that it’s not true varnish, doesn’t mean It’s not. I use techniques. You use applied coats of pre prepared  colophony. 

[joerobson]

There are certainly many ways to do this job well.

Joe

[sospiri]

2 minutes ago, joerobson said:

There are certainly many ways to do this job well.

Joe

But what’s the right one?

[David Burgess]

Deleted, since I failed to quote what I was responding to. See below.

[David Burgess]

1 hour ago, joerobson said:

In varnish maker's terms a varnish of 1:1 is the most oil a varnish can hold and still be considered polishable.

Joe

I'm not understanding that. Pretty much anything is polishable, with knowledge of the right techniques and materials.

Well, maybe not a fresh corn syrup or molasses coating.

Sheesh, I have even successfully polished 100% dried linseed oil, and 100% dried tung oil coatings.

[nathan slobodkin]

1 hour ago, joerobson said:

I have discussed this with both M. Brandmair and JP Echard.  The scientific analysis is lacking.   Observation however gives us more information.   The varnish which is in first contact with the wood seems likely to be 4 resin to 1 oil.  However the making of that varnish retains flexability.  A very short oil varnish would be far more brittle than we observe and would make varnishing a cello very difficult.

In varnish maker's terms a varnish of 1:1 is the most oil a varnish can hold and still be considered polishable.

Joe

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

[Peter K-G]

Hmm..

If I cook varnish with one hour reduced resin 1:1 ratio oil, or if I cook with 10 hours  reduced resin 1:1 oil ratio. How is this even measurable. 

[joerobson]

23 minutes ago, David Burgess said:

I'm not understanding that. Pretty much anything is polishable, with knowledge of the right techniques and materials.

Well, maybe not a fresh corn syrup or molasses coating.

Sheesh, I have even polished 100% dried linseed oil coatings.

David,

High oil varnishes have the best sheen "off the brush ".  They CAN be polished,  but they may sweat in high humidity.

Joe

[Bill Yacey]

23 minutes ago, Peter K-G said:

Hmm..

If I cook varnish with one hour reduced resin 1:1 ratio oil, or if I cook with 10 hours  reduced resin 1:1 oil ratio. How is this even measurable. 

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.

[joerobson]

3 minutes ago, Bill Yacey said:

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.

Bill,

That would be standard operating procedure in varnish making.

Joe

[Bill Yacey]

9 minutes ago, joerobson said:

Bill,

That would be standard operating procedure in varnish making.

Joe

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.

[David Burgess]

2 hours ago, joerobson said:

David,

High oil varnishes have the best sheen "off the brush ".  They CAN be polished,  but they may sweat in high humidity.

Joe

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?

 

[Michael Szyper]

2 hours ago, sospiri said:

But Echard says the rosin/oil layer is not in contact with the wood, only the oil layer and the rosin/oil layer that sits on top of that.

In which publication he is claiming this?

[Jim Bress]

2 hours ago, nathan slobodkin said:

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

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

[Davide Sora]

2 hours ago, sospiri said:

But Echard says the rosin/oil layer is not in contact with the wood, only the oil layer and the rosin/oil layer that sits on top of that.

 

45 minutes ago, Michael Szyper said:

In which publication he is claiming this?

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

[Davide Sora]

12 minutes 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

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