Stradivari's golden ground varnish


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13 hours ago, sospiri said:

What sort of varnish are you using? 

I have noticed that people around me are getting bigger and the super sizing seems to start younger. I blame the internet.

I use Birchwood Casey  Tru-Oil gunstock finish. It has a low viscosity so it can be applied with very thin coats.

The straight sided 240ml bottle is tall with a narrow base so I put it into a deep coffee cup to prevent it from tipping over--that's my main contribution to violin making technique.

I lightly sand the wood after each coating with wet 600 mesh sandpaper.  The pores are then eventually filled without using a thick coating.

 

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12 hours ago, MikeC said:

Didn't Echard only find linseed oil?  And did B&G determine that it was a lean varnish?  I don't have the book so I don't know.  Could there be a resin there that was not detected?  

Yes and yes and (maybe)yes.

But Brandmair does not find oil but proteins (casein) in wood, instead Echard never finds proteins, Malagodi (researcher at the Cremona Museum) always finds proteins.
Isn't it puzzling?:D:):unsure::(

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2 hours ago, Davide Sora said:

Yes and yes and (maybe)yes.

But Brandmair does not find oil but proteins (casein) in wood, instead Echard never finds proteins, Malagodi (researcher at the Cremona Museum) always finds proteins.
Isn't it puzzling?:D:):unsure::(

Very puzzling.  Are you sure it's casein?  Or just an assumption?  I never heard of Malagodi.  Are there any published papers from him? 

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1 hour ago, MikeC said:

Very puzzling.  Are you sure it's casein?  Or just an assumption?  I never heard of Malagodi.  Are there any published papers from him? 

Brandmair speaks specifically of casein, I don't remember which method was used but it is a special analysis that identifies milk proteins (sorry for my "approximate" scientific definition:P).

There are several papers written by Malagodi, he is the head of the chemical analysis department of the Cremona Violin Museum since its opening in 2011. For example the one mentioned in this post :

 

 

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15 hours ago, Michael_Molnar said:

I really wish Brandmair sold a cheaper version of her book, say, an electronic version.

I am frustrated by the lack of readership. I also encourage those who have the book to reread as much as possible. Time distorts memories.

I wish they did too,  it's out of my price range for now.  

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17 hours ago, Michael_Molnar said:

I really wish Brandmair sold a cheaper version of her book, say, an electronic version.

I am frustrated by the lack of readership. I also encourage those who have the book to reread as much as possible. Time distorts memories.

It is also important to differentiate between the two author's assessments.

Also it is hard to remember to read the text when the pictures are so good.

on we go,

Joe

 

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On 12/24/2020 at 6:40 PM, Davide Sora said:

Brandmair speaks specifically of casein, I don't remember which method was used but it is a special analysis that identifies milk proteins (sorry for my "approximate" scientific definition:P).

There are several papers written by Malagodi, he is the head of the chemical analysis department of the Cremona Violin Museum since its opening in 2011. For example the one mentioned in this post :

 

 

Casein or Cysteine? Which could come from hydrolised Keratin?

 

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On 12/23/2020 at 5:00 PM, joerobson said:

The slow capillary action of the oil in the wood softens the details in a way that over polish cannot correct.

22 hours ago, Advocatus Diaboli said:

Doesn’t that apply mainly to heavy coats of oil, or oil with poor drying properties?  

I remember from my aerospace days that oils continue to crawl over surfaces, and we needed seals or a coating of oil non-wetting material to block it off.

In some recent tests, I used tung oil on bare rib stock, applied in various ways (thin, thick, with fumed silica and without), and in every case you could turn over the piece and see that the oil had made its way completely through the wood.  

Bottom line as I see it:  if the oil dries slow enough, it's going to continue into the wood, no matter how "thin" you try to make the coating.  It will vary depending on the angle of the cut... on places with absolutely no runout, it might be prevented.

 

 

One other random note:  according what found on color, brown is dark orange, and conversely orange is bright brown.  But what is "golden"?  Yellowish bright brown?

 

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4 hours ago, Don Noon said:

I remember from my aerospace days that oils continue to crawl over surfaces, and we needed seals or a coating of oil non-wetting material to block it off.

In some recent tests, I used tung oil on bare rib stock, applied in various ways (thin, thick, with fumed silica and without), and in every case you could turn over the piece and see that the oil had made its way completely through the wood.  

Bottom line as I see it:  if the oil dries slow enough, it's going to continue into the wood, no matter how "thin" you try to make the coating.  It will vary depending on the angle of the cut... on places with absolutely no runout, it might be prevented.

I'm currently repeating some experiments I did decades ago, because sometimes it's easier and less time consuming to do a new experiment, than sift through a two-foot pile of old varnish experiment notes. :lol:

I agree that combining a drying oil with silica doesn't prevent the oil from spreading. An easy way to see this is to put a puddle of the combination on a paper towel. The silica will stay pretty much where you put the original puddle, and the drying oil will continue to spread until it dries, or becomes a resin. Spreading of the oil can be reduced (almost eliminated) by exposure to intense sunlight or UV right away.

I'm not sure that what can be learned from lubricating oils meshes well with knowledge about drying oils. Lubricating oils and greases (ideally) are formulated to maintain their original properties for a long time, and under a wide range of conditions. This is quite different from what we desire/expect from linseed oil or tung oil.

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On 12/23/2020 at 10:35 AM, joerobson said:

 

Linseed oil can be an effective Ground....along with a variety of other materials.  However my observation is that over time it does not provide the optical properties of the classic Cremonese Ground.   The ancient ground retains a crispness of detail and a degree of deep complex reflection that defines it's beauty and distinctive appearance.

Linseed oil has a similar effect when freshly applied.   However , due to capillary action and the effects of light it does not retain this appearance.

 

On 12/23/2020 at 5:23 PM, David Burgess said:

It very well might, if it were periodically smeared with an oil-containing polish, or "French polished" several times, like just about every example of a 17th century violin has been.

 

On 12/23/2020 at 8:00 PM, joerobson said:

David,

I disagree.   The slow capillary action of the oil in the wood softens the details in a way that over polish cannot correct.

Joe

While linseed oil expands upon initial drying, it later contracts, incorporating air voids which interfere with transparency. Filling these air voids with some kind of oil or grease (which is closer to the refractive index of the varnish film than air) will increase transparency. Why do you think that products like Hill Polish, and Lemon Pledge became so popular?

There's more going on with the "effect" of transparency, like surface smoothness, but that isn't what I'm focusing on at the moment.

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14 hours ago, sospiri said:

Casein or Cysteine? Which could come from hydrolised Keratin?

 

Casein.

Brandmair examines an extremely limited number of samples (this is the real problem in all the researches of other authors too) finds casein in one case, ovalbumin and collagen in another case and identifies generic proteins in the other cases, if I remember correctly.

Here an excerpt from his essay, the first (p. 71/72) is related to the analysis of a cello of 1730 where she found casein, the second (p.107 / 108) are its general conclusions :

600619438_BrandmairproteinsDSC_8712rid.thumb.jpg.88d79bb5be505d55cf799fde0950a46f.jpg594968055_BrandmairproteinsDSC_8710rid.thumb.jpg.18d15bddd78fca1d0372995e5f66aba5.jpg

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5 hours ago, David Burgess said:

I'm currently repeating some experiments I did decades ago, because sometimes it's easier and less time consuming to do a new experiment, than sift through a two-foot pile of old varnish experiment notes. :lol:

Looks like I'm going to have to do that also.  Back some time ago I applied linseed oil to some rib stock and it never soaked through but that sample is long gone.  I'll try it with paper this time.  This time of year there is not much solar UV available though.   I remember at the time thinking LO has a dullness or lack of reflectivity that I didn't like.   

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35 minutes ago, Davide Sora said:

One of the problems in evaluating the effect of linseed oil is that its refractive index increases with time and oxidation, so what you see right away could be misleading. With this, I don't want to encourage anyone using the oil straight on wood, I don't like it.

Thanks for the information Davide. But why not put linseed oil straight on the wood if it can be sealed with a very small amount?

Richard's photograph shows a penetration only one cell deep. 

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7 hours ago, David Burgess said:

I'm currently repeating some experiments...

I agree that combining a drying oil with silica doesn't prevent the oil from spreading. An easy way to see this is to put a puddle of the combination on a paper towel. The silica will stay pretty much where you put the original puddle, and the drying oil will continue to spread until it dries, or becomes a resin. Spreading of the oil can be reduced (almost eliminated) by exposure to intense sunlight or UV right away.

I'm not sure that what can be learned from lubricating oils meshes well with knowledge about drying oils. Lubricating oils and greases (ideally) are formulated to maintain their original properties for a long time, and under a wide range of conditions. This is quite different from what we desire/expect from linseed oil or tung oil.

I'm trying out some experiments now as well, to see how UV affects oil penetration and spread.  Some drops of various things are on a piece of white paper hung vertically in the lightbox, and an identical set is in a closed metal cabinet.

Sure, lubrication oils probably wet better and definitely are made not to dry, but until drying oils dry, they act a lot like lubricating oils.  

One other point... if a thinner is involved, there are two phases of "drying"... one where the thinner evaporates, and another where the oils polymerize.  Spreading might slow down after the first, but won't stop until the second.

50 minutes ago, sospiri said:

Thanks for the information Davide. But why not put linseed oil straight on the wood if it can be sealed with a very small amount?

Richard's photograph shows a penetration only one cell deep. 

If the photograph is of an area where there is zero runout, then there can't be penetration farther than one cell, even with oil spread.  With figured maple, or on sloped cuts of arching, that's different, and it matters how quickly the oil dries vs. how fast it spreads by capillary action.  Try sealing the endgrain of spruce with linseed oil sometime... it's a sponge.  Or figured maple... it will sit on the surface between flames, and sink in badly on the flames.

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19 hours ago, JacksonMaberry said:

I'd gladly settle for an academic paper sans Greiner's work and the photos. 

 

17 hours ago, joerobson said:

It is also important to differentiate between the two author's assessments.

Also it is hard to remember to read the text when the pictures are so good.

on we go,

Joe

 

Ahh. We are building a consensus about the two authors. We agree.

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