refractive ground question

[Craig Tucker]

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

If I'm not mistaken, Violins88 (John Schmidt) tried the shrimp shell idea (ala Dr. N) and likewise had no luck.

[actonern]

"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 too had a miserable time getting any kind of adhesion with oil varnish... and there was none of that Sacconi described "salmon" color... clear as water.

Won't use it again...

E

[joerobson]

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

Bruce,

" 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."

I think the answer is yes. but I don't own the book [yet] either. I will ask her and get back to you. I have suggested she join MN...I'll do that again.

Joe

[Brian McLinden]

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.

It seems important to use kasil not alone as a finishing step, but by first boiling other substances in it before application. I stripped a violin and re-did it using kasil and rosin and 2 other things all as one coating step, and the instrument appears to have good reserve. YMMV, of course, depending upon details of procedure.

[MikeC]

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

is that grayish area in the center bare wood in the UV pic? in the color pic that area seems to have nearly as much color as the un-worn areas

I read a varnish recipe in an old book 1800s it was described as very brilliant (whatever that means) and very durable, and having a gold color, and from the ingredients I think an analysis of it would probably find silica, potassium, calcium, maybe sodium elements, I may test it out and see how it looks.

[violins88]

If I'm not mistaken, Violins88 (John Schmidt) tried the shrimp shell idea (ala Dr. N) and likewise had no luck.

Yes, that is correct. I made the shrimp shell recipe by boiling shrimp shells for 8 hours, then washing, then dissolving in vinegar. It made the wood REALLY dull. No ring whatever.

[fiddlecollector]

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

Oded , ive actualy used silk before and it wasnt too bad for sealing wood surfaces.Dont know what the person you mentioned did but I bought some raw silk cocoons ,dissolved them in a Zinc chloride/ethanol/water solution. Then removed the salt by dialysis using some dialysis tubing membrane and d-ionized water.I then evaporated some of the excess water off and had a solution that resembled gum arabic. The resulting solution of silk fibroin in water is supposed to be almost identical to the stuff held in the silk gland .

It dried on wood to a very thin coating that had a slight sheen and seemed to prevent dyes or pigments from penetrating the surface.

RobertDo may like to comment as it is more his field working with proteins,etc..

[David Burgess]

is that grayish area in the center bare wood in the UV pic? in the color pic that area seems to have nearly as much color as the un-worn areas

I would say "Yes", but it probably wouldn't be correct to call it bare wood. Clean away the dirt and contaminants, and it can look quite light under normal (non UV)lighting. The wood can darken very quickly once the "ground" has worn away.

If you remove original varnish mechanically, all the way down to raw wood, you won't find that darkness at any stage. (again, I'm speaking of the darkness in the non UV photo)

[Bruce Carlson]

is that grayish area in the center bare wood in the UV pic? in the color pic that area seems to have nearly as much color as the un-worn areas

I read a varnish recipe in an old book 1800s it was described as very brilliant (whatever that means) and very durable, and having a gold color, and from the ingredients I think an analysis of it would probably find silica, potassium, calcium, maybe sodium elements, I may test it out and see how it looks.

No, I wouldn't call it bare wood either but what is there is not creating any thickness above the wood surface. If the wood remains fairly clean then there is still some ground protecting it because, as David already mentioned, it would be much dirtier in appearance.

In the gray area the greenish layer (or at least what my camera under UV lighting conditions "sees" as greenish) is absent. On top of this very thin greenish layer is a brighter yellowish layer followed by the dull brown layer on top which is more charged with color. These top two layers are thick and you can see the wear gradient whereas the lower greenish layer is either there or it isn't; a feature which tells me it must be quite thin. I feel the greenish layer is a separate layer from the bright yellowish layer because in places where the yellowish varnish has chipped off the greenish layer it can still be seen underneath as if they do not adhere very well to each other but the greenish layer stays in place. And besides, that greenish layer if built up thicker would not become bright yellow under UV. I think it is separate.

I'll have to see if I can make up another photograph showing this feature more clearly.

Bruce

[robertdo]

I am afraid my knowledge in the silk department is very limited...

But using silk (worm or spider) would make sense (although very expensive I would guess, and not possible for spider silk) if one is looking for a protection coat that would be strong, flexible and that would not let pass big molecules like a pigment. Since silk is a fibrous protein that makes long chains that can entangle themselve creating a sieve, it's a good candidate. That is why I guess some people used hide glue which is collagen. But hide glue becomes brittle. Like others I use gelatine/albumine, which is a good compromise I suppose. Also in the old time they might have thought as the ground as a shell and so like an egg shell maybe they realised they could mix a protein with some salt (carbonate sodium or else). But if I read what has been said here, the result is not up to the expectations.

you know since I read this post and since I was actually making an acrylamide gel I thought that this could be a solution were it not for the acrylamide being pretty toxic when not polymerised. But once polymerised it become a gel very flexible that is use to separate protein according to their size (in other words it would probably act as a barrier against some pigments). Just for fun I might try to lay a coat of acrylamide on some wood scrap and see what happens.

[joerobson]

No, I wouldn't call it bare wood either but what is there is not creating any thickness above the wood surface. If the wood remains fairly clean then there is still some ground protecting it because, as David already mentioned, it would be much dirtier in appearance.

In the gray area the greenish layer (or at least what my camera under UV lighting conditions "sees" as greenish) is absent. On top of this very thin greenish layer is a brighter yellowish layer followed by the dull brown layer on top which is more charged with color. These top two layers are thick and you can see the wear gradient whereas the lower greenish layer is either there or it isn't; a feature which tells me it must be quite thin. I feel the greenish layer is a separate layer from the bright yellowish layer because in places where the yellowish varnish has chipped off the greenish layer it can still be seen underneath as if they do not adhere very well to each other but the greenish layer stays in place. And besides, that greenish layer if built up thicker would not become bright yellow under UV. I think it is separate.

I'll have to see if I can make up another photograph showing this feature more clearly.

Bruce

Bruce,

Concentrating on that first contact of varnish with the wood: Over the ground [in the wood] the material must be a cooked vehicle material [varnish] otherwise it would be vulnerable to its original solvents. This material must be very tough and resistant to environmental factors. It must also have little or perhaps no tendency to self-level or build film thickness. I see this as a very lean varnish applied thin. Tough stuff!

Joe

[scordatura]

What are peoples opinions on the source of the color of the ground? Is it inherent in the ingredients or something added to create the color? I know that some are using shellac but if we subscribe to the notion that the cremonese were not using shellac what is yielding the gold/honey color?

[Jeffrey Holmes]

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

Thanks Bruce. Precisely.

I think John Becker referred (in his technical paper on Bergonzi instruments) to the visual effect remaining when the color coat chips/wears away on del Gesu instruments, as revealing "halos" of the isolation coat... which is pretty well illustrated in your photos.

[Craig Tucker]

No, I wouldn't call it bare wood either but what is there is not creating any thickness above the wood surface. If the wood remains fairly clean then there is still some ground protecting it because, as David already mentioned, it would be much dirtier in appearance.

I'll have to see if I can make up another photograph showing this feature more clearly.

Bruce

Thanks Bruce, top notch photos again - as usual.

I'll admit that, even though I have known that these "alternate light source" forensic type of techniques have existed, I have not really made much use of them yet.

The really valuable thing going on here, that I can see, is that mechanical things (regarding wear) that are not clearly visible in normal light, or that might be not entirely clear - become very obvious with UV light.

Do you have any idea what color bare wood would show, if an area where all the real or imagined coatings have either not been applied or have worn off?, - like a *control* area?

Perhaps the neck, or the inside surface of the plate, or where a clean beak has occurred and virgin wood is exposed? What would it look like under UV?

I also wonder if anyone has taken up a study of wood in general, unworked wood, wood that has been processed in a known way, old barn wood, weathered wood, antique wood and etcetera, in order to establish a sort of base line regarding what we should ordinarially expect to see under UV light?

Do you know of such a thing?

I think something like that would help many viewers (myself included), who haven't had first hand experience with this sort of thing, make sense of what they (we) were looking at.

(I realize that you probably didn't sign up for providing anyone with this sort of "basic education" in violin forensics, I'm just asking because I think if such a thing does exist - you may know of it...)

[Janito]

Just for fun I might try to lay a coat of acrylamide on some wood scrap and see what happens.

I would be willing to wager $1 that the acrylamide gel would kill the sound of a violin, irrespective of its effects on wood appearance.

[joerobson]

ct,

"Do you have any idea what color bare wood would show, if an area where all the real or imagined coatings have either not been applied or have worn off?, - like a *control* area?"

At this late date bare wood would not be an indicator of original wood color. We also do not know if any colorant was added to the wood by the makers.

What we do know is that wood in the presence of light [both UV and visible] undergoes color transformations, some of which are visible under the varnish and in differing degrees in areas which have only ground and isolation coat or are just bare wood. The degree to which this color is effected by the varnish is an interesting area for study...but I think these changes have more to do with the life of a particular instrument....was it in a case? in a window? in a vault? in the leaky attic????

on we go,

Joe

[David Burgess]

Do you have any idea what color bare wood would show, if an area where all the real or imagined coatings have either not been applied or have worn off?, - like a *control* area?

Newish spruce is kind of a chocolate milk color (darker than the "sealer" areas in Bruces UV photo), and goes more towards chocolate with some surface browning from age. One needs to be careful with these descriptions though, because the colors observed will partly depend on the ratio of UV to visible light in the light source.

[Craig Tucker]

Thanks Joe and David, for the answers.

Here's a stupid question.

Can I just go to Home Depot and buy a UV bulb for a standard fixture, or does this type of UV entail something a bit out of the ordinary?

My shop can be darkened quite easily, and it wouldn't be difficult to rig an area for checking these things out firsthand.

[David Burgess]

Thanks Joe and David, for the answers.

Here's a stupid question.

Can I just go to Home Depot and buy a UV bulb for a standard fixture, or does this type of UV entail something a bit out of the ordinary?

My shop can be darkened quite easily, and it wouldn't be difficult to rig an area for checking these things out firsthand.

You can see a lot with a standard "BLB" bulb. I don't think it's too much different from the "spec" museum lamp we had at Oberlin last year, but I haven't had them side by side.

I think I was seeing slightly different things and colors many years ago when I was using a high-pressure mercury discharge woods lamp. That setup seemed to emit almost no visible light, and make things fluoresce very strongly.

[LinkMan]

Thanks Joe and David, for the answers.

Here's a stupid question.

Can I just go to Home Depot and buy a UV bulb for a standard fixture, or does this type of UV entail something a bit out of the ordinary?

My shop can be darkened quite easily, and it wouldn't be difficult to rig an area for checking these things out firsthand.

CT ask a stupid question? Never!!!

U.V. Flashlights

The problem though with U.V. seems to be one of getting the right wavelength, when comparing to what someone else is seeing.

It would be the equivalent of saying in the Visible Light Spectrum, that Stradivari's varnish is say perhaps a green color when using only the green visible light, having filtered out the rest.

This same thing happens in the U.V. part of the Spectrum when looking for the Salmon Pink colour, if you are not using the same wavelength as Sacconi, then you will not see the same color fluoresce.

[Jeffrey Holmes]

I think I was seeing slightly different things and colors many years ago when I was using a high-pressure mercury discharge woods lamp. That setup seemed to emit almost no visible light, and make things fluoresce very strongly.

That was a heck of a lamp... UV Goggles recommended.

[MikeC]

maybe the UV lights that mineral collectors use would work better than the home depot variety?

http://www.uvsystems.com/store/home.php

[LinkMan]

That was a heck of a lamp... UV Goggles recommended.

I Googled Goggles

[Melvin Goldsmith]

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

...................

Bruce I think what you refer to here as the 'brown layer' is called the 'stain layer' in the book...the nature of the stain is as yet undiagnosed but these days more visible under UV than visible light (at least...according to my understanding of the book). I'd have to have the book at hand to diagnose your photo by the books criteria though.

I certainly need to re read the Brandmair book a few times. Greiner summarized the Brandmair teams findings in terms of 4 layers.

1/ 'Impregnation' ....ie a protein size of some kind as yet undetermined

2/ 'Stain and pore filling'.....stain yet to be identified...pore filling maybe a wipe over of colour varnish

3/ 'Base varnish' a clear/ slightly yellow layer

4/ 'Coloured varnish'

[joerobson]

Thanks Bruce. Precisely.

I think John Becker referred (in his technical paper on Bergonzi instruments) to the visual effect remaining when the color coat chips/wears away on del Gesu instruments, as revealing "halos" of the isolation coat... which is pretty well illustrated in your photos.

Jeffery,

Am I correct? You had a hand in this study?

Joe