refractive ground question

[scordatura]

Does anyone have high resolution images or links to high resolution images of Petrus of Mantua violins? I did a quick search on google and did not find anything spectacular.

This summer I may be able to provide some as a friend owns a Petrus.

[Jeffrey Holmes]

Well, for me the ground is the stuff immediately under the colored varnish that appears to be another coat of varnish, of varying thickness, mostly colorless but having a slight honey-colored cast that becomes more apparent with increasing thickness, and which appears to touch and slightly infiltrate the first couple of cell thicknesses of the wood. It can be so thick that pores are completely filled, or so thin that they aren't, and isn't inevitably in Cremonese work, or is so thin that it's not apparent. It's the stuff that I have always associated with the beautiful look of a nice Cremonese paint job, in that if it's not there, things don't look as nice as what people think of when they think of as a great Cremonese "varnish" job. The stuff that doesn't wear away quickly when the colored varnish wears.

That's in the traditional understanding, not including all the varied "invisible" things that each new round of analyzers seem to come up with while simultaneously not seeing any of the "invisible" things that last year's favorite varnish analysis discovered. :-)

"Traditional understanding" reminds me of what I hear at board meetings when the old guard doesn't want to discuss something.

I believe I'm talking about the same layers Sacconi wrote about. Agree or disagree with his conclusions, I think he was a pretty decent observer. John Becker also referred to these layers in his technical paper for the Bergonzi exhibit.

Seriously; A significant factor concerning what I find separates the appearance of some Cremonese instruments from others (the appearance of the varnish and how the color coat "wears") is the thickness of this isolation layer... the less colored varnish you speak of, so we're probably speaking of the same idea with different terminology. This isolation layer does often seem to stop at, or just above, the surface of the wood, however, and what I refer to as the ground is present. I'm not cocky enough to claim that what is applied as a ground is a different compound or material than the isolation layer, or that it's the same stuff on every Cremonese instrument... but it does behave differently. That may be because it is partially absorbed into the top layer of the wood, combines with other materials on the wood surface (materials that may have been applied or simply used to prepare the surface), may be because there is less oil in it (or a different viscosity when applied), that it was worked slightly before the next coat (which BTW, fits with finishing methods of other wood products during the same period), or that it's a different material. Maybe it's a combination of things.

[joerobson]

Jeffery,

Seriously; A significant factor concerning what I find separates the appearance of some Cremonese instruments from others (the appearance of the varnish and how the color coat "wears") is the thickness of this isolation layer... the less colored varnish you speak of, so we're probably speaking of the same idea with different terminology. This isolation layer does seem to stop at, or just above, the surface of the wood, however, and what I refer to as the ground is present.

Yes! This balance of reflectivity and color impact was an education on the Bergonzi instruments at the exhibition.

I'm not cocky enough to claim that what is applied as a ground is a different compound or material than the isolation layer, or that it's the same stuff on every Cremonese instrument... but it does behave differently. That may be because it is partially absorbed into the top layer of the wood, combines with other materials on the wood surface (materials that may have been applied or simply used to prepare the surface), may be because there is less oil in it, that it was worked slightly before the next coat (which BTW, fits with finishing methods of other wood products during the same period), or that it's a different material. Maybe it's a combination of things.

Though it is my opinion that the ground and isolation layer were self-similar materials with different purposes, I think it is important to approach this work with an open and inquisitive mind. There is such a variation in appearance among the classic Cremonese instruments that we must keep in mind this was an ongoing and learning process for the makers of that time also. We have all heard too many times that the "answer" has been found...My work is not to claim historical authenticity...ever...that is the work of conservators, restorers, scientists, and violin historians. My job is to isolate what we see and find tools useful in re-creating what we see.

on we go,

Joe

[MikeC]

are you guys saying there are three layers? Ground, Isolation, and color varnish?

[MikeC]

Does anyone have high resolution images or links to high resolution images of Petrus of Mantua violins? I did a quick search on google and did not find anything spectacular.

This summer I may be able to provide some as a friend owns a Petrus.

I hope you can get some pics of the one your friend owns and show them here. I googled it also and didn't find much.

[joerobson]

are you guys saying there are three layers? Ground, Isolation, and color varnish?

Mike,

In reality there are many variations, so being exact is kind of like roping water....but...I find this distinction a valuable way to approach seeing and figuring out strategies for application.

on we go,

Joe

[Janito]

are you guys saying there are three layers? Ground, Isolation, and color varnish?

The order would be: wood - isolation layer - ground - colour varnish; correct?

[joerobson]

The order would be: wood - isolation layer - ground - colour varnish; correct?

Janito,

For my eye: wood, ground, isolation layer, varnish [colored or not]

Joe

[MikeC]

how do you know there is a layer between the ground and the varnish? Is it visible? What does it look like? color? thickness?

[actonern]

Hi Joe:

I'm interested to know whether you have drawn any conclusions as to whether the ground was simply uncolored varnish of the same type as used on subsequent color layers... a simple barrier to prevent colored varnish from mudding up the spruce or locking the grain on maple...

Best regards

E

[Brian McLinden]

Janito,

For my eye: wood, ground, isolation layer, varnish [colored or not]

Joe

Sacconi spoke of a "silicate of calcium and potassium."

Why not consider this perhaps modern approach -

ground: kasil / rosin /...

isolating: borax / shellac /...

What ions or chemicals need to be prior to (and perhaps above?) the ground layer?

[Craig Tucker]

Sacconi spoke of a "silicate of calcium and potassium."

Why not consider this perhaps modern approach -

You're welcome to try them.

I have used potassium silicate before (ala Sacconi - the layer that would "ossify" the wood, if I recall correctly) and it was a complete disaster.

Of course, I cannot say if what I used was applied correctly, or if it was what was available traditionally or not. But it's cheap and plentiful - which is an advantage compared to something like using fused Baltic Amber - so, there's no reason not to experiment with it if you feel like it's a likely path.

I'll be frank, I just don't like it - plain and simple.

[Brian McLinden]

You're welcome to try them.

I have used potassium silicate before (ala Sacconi - the layer that would "ossify" the wood, if I recall correctly) and it was a complete disaster.

Of course, I cannot say if what I used was applied correctly, or if it was what was available traditionally or not. But it's cheap and plentiful - which is an advantage compared to something like using fused Baltic Amber - so, there's no rerason not to experiment with it if you feel like it's a likely path.

I'll be frank, I don't like it - plain and simple.

What else did you use with the kasil, or was that a disaster because you used only kasil in a finishing step?

[Guest]

Janito,

For my eye: wood, ground, isolation layer, varnish [colored or not]

Joe

Joe

wood, aged color, ground, isolation layer, varnish? Are these the steps you are using now? Does the iso layer mean a clear varnish layer to add depth?

[Jeffrey Holmes]

how do you know there is a layer between the ground and the varnish? Is it visible? What does it look like? color? thickness?

Yes. What I'm referring to is visible (especially when working on/with the instruments), but varies in thickness from maker too maker and period to period (same maker). It's probably less "color charged" varnish, but I have no wish to start another violin related "tale".

[Bruce Carlson]

Yes. What I'm referring to is visible (especially when working on/with the instruments), but varies in thickness from maker too maker and period to period (same maker). It's probably less "color charged" varnish, but I have no wish to start another violin related "tale".

Here are two shots of the same area on the back of a 'del Gesù', one in normal light and one in UV. You can see two distinct layers here. I think this is what Jeff meant.

In this instance it is easy to make out the lower less colored layer (bright yellow) from the upper layer (dull brownish). If you look carefully around the edges of the worn areas you can, at least I think I can, make out a very thin third layer (more greenish and less bright)next to the darkest color which is almost bare wood. EDIT: is this lower layer (greenish in my photo) what Brandmeier calls the brown layer? I don't have a copy of the book yet.

Bruce

[captainhook]

What else did you use with the kasil, or was that a disaster because you used only kasil in a finishing step?

What is "kasil?" I'm a chemist and that's a new one on me.

[MikeC]

What is "kasil?" I'm a chemist and that's a new one on me.

a brand of potassium silicate, I googled it

http://www.pqcorp.com/msds/kasil_6.pdf

[Janito]

Janito,

For my eye: wood, ground, isolation layer, varnish [colored or not]

Joe

I don't understand why you would need an 'isolation' layer between ground and varnish?

[Janito]

In this instance it is easy to make out the lower less colored layer (bright yellow) from the upper layer (dull brownish). If you look carefully around the edges of the worn areas you can, at least I think I can, make out a very thin third layer (more greenish and less bright)next to the darkest color which is almost bare wood.

Are you saying that this thin layer is against the wood under the 'yellow' material? (I cannot see it on my screen).

[Don Noon]

You're welcome to try them.

I have used potassium silicate before (ala Sacconi - the layer that would "ossify" the wood, if I recall correctly) and it was a complete disaster.

Of course, I cannot say if what I used was applied correctly, or if it was what was available traditionally or not. But it's cheap and plentiful - which is an advantage compared to something like using fused Baltic Amber - so, there's no reason not to experiment with it if you feel like it's a likely path.

I'll be frank, I just don't like it - plain and simple.

I tested out the potassium and sodium silicates, with similar (awful) results. It seemed like a good idea... a glassy substance applied to the wood to stiffen the wood and give sparkling, crystalline highs. Unfortunately, it doesn't work. My test samples got heavier and more damping, and the instrument I tried it on got duller and quieter.

[Craig Tucker]

What else did you use with the kasil, or was that a disaster because you used only kasil in a finishing step?

I just got back from having my taxes done, and I feel like a big weight has been removed from my back...

Yes, I used a modern chemical potassium silicate. Very thin, watered down, and worked back with an abrasive as a ground coat to, as Sacconi put it, "ossify" the wood surface and to isolate it from any further coatings or varnish.

(Ref. The “Secrets” of Stradivari, pgs. 159 - 167)

Of course, since we are talking about the ideas coming from Sacconi, I would invite anyone who would like to try it, to go ahead and obtain theirs by melting, in a sealed crucible, silica, charcoal and potash which has been obtained from the ashes of the "green growth of the grape vine, or, even better from the ashes of the sediment of the grape pressings", reduce it to powder, add it to boiling water, boil again and decant ..., etc., etc.

The ideas, the theories, and the practices are usually very different things.

Like Mr. Noon, I found that the tone suffered noticeably, too much of a "good thing" is my guess, and I also had pretty bad adhesion problems... not the potassium silicate adhering to the wood, but the oil varnish over the silicate wanting to peel off.

I too would like to hear from any other makers who have actually tried some of these methods, and in particular some of the things recommended by Sacconi. Where does it seem he was on the right track, and where did he have it wrong?

[Craig Tucker]

I tested out the potassium and sodium silicates, with similar (awful) results. It seemed like a good idea... a glassy substance applied to the wood to stiffen the wood and give sparkling, crystalline highs. Unfortunately, it doesn't work. My test samples got heavier and more damping, and the instrument I tried it on got duller and quieter.

Yes, I admit it sounded good on paper.

[Oded Kishony]

I too would like to hear from any other makers who have actually tried some of these methods, and in particular some of the things recommended by Sacconi. Where does it seem he was on the right track, and where did he have it wrong?

I personally knew someone who tried the silk cocoon idea. Went to great lengths to grow silk worms, soak the cocoons and extract the nectar etc etc. No one seemed to like the result.

Oded

[joerobson]

I don't understand why you would need an 'isolation' layer between ground and varnish?

Janito,

I see two functions here. This isolation layer is IMHO a different sort of varnish: very lean and very tough. It, combined or not with a coat of gold or "colorless" top varnish, determines how close to the wood the color appears and how deep the reflectivity of the ground appears. Varying this is an interesting tool.

Joe