Proteins in Varnish Systems

[jezzupe]

9 hours ago, Don Noon said:

I'll continue to disagree.

Could you elaborate on not so much why you disagree {you can if you want} but perhaps more what your "theory" is as to whats going on or what we see? and what part about it is "mysterious/head scratching/unknown" to you/us?

To Peter KG, ya I was talking more specifically to "hide glue" as not being very transparent, but ya thats a nice "film" you have there and is what I suggest everyone do "make "fruit roll ups" film" out of varnishes so you can see the film alone, and as Jackson suggests, they can make for an excellent survival food right up there with hard tack.  :}

[uguntde]

On 3/15/2022 at 12:56 AM, John Harte said:

Thank you for the paper you reference.  Something akin to hydrothermal degradation could apply in a varnish making context.  However protein presence within a varnish system may not have anything to do with the actual cooking of a varnish.

Do you think that various FTIR analyses of old violin varnish systems are capable of detecting proteinaceous material presence as claimed?  Are amide I, II and III absorptions an indication of protein, polypeptide, peptide or amino acid presence or something else again?  There also often seems to be a leap between amide I, II and III absorptions and conclusions that something like casein glue or similar is involved.

Yes and no. You can see those indeed, but these are not unique identifiers. Explained very well in this lecture:

https://www.chem.uwec.edu/chem455_s05/pages/Manuals/FTIR_of_proteins.pdf

In what I have written I have also not thought much about casein which contains (very simple) proteins - you see two lines. But they do shift when metals are present, there are publications about this.

These proteins can probably be rehydrated, there is no tertiary structure, but they are not so well characterised. Main interest in these proteins is that they cause allergies.

Casein would just act as a filler on the surface. Or maybe also to close the pores as it sticks. I am not sure whether this is good enough to prevent pigments running up the grain lines. It won't look great to have a clot of casein at the end of f-holes.

 

[Don Noon]

9 hours ago, jezzupe said:

Could you elaborate on not so much why you disagree.

Just lots of experiments with various grounds and varnishes.  Water-born, and to a lesser extent alcohol based grounds just tend to wash out contrast in flames, as a separate effect from color.

[jezzupe]

3 hours ago, Don Noon said:

Just lots of experiments with various grounds and varnishes.  Water-born, and to a lesser extent alcohol based grounds just tend to wash out contrast in flames, as a separate effect from color.

It seems your talking about delineation within grain celebration , or oil tend's to make "the most" of grain celebration whereas water and shellac/spirit you get delineation but it seems to have a monochromatic cast of the base color of the finish riding along with whatever you get as far as celebration goes.

Well if I'm correct about your thoughts, I still think the factors I talked about effect those things, but I do certainly agree with what you said being an issue or challenge to overcome.

 

[John Harte]

11 hours ago, uguntde said:

Yes and no. You can see those indeed, but these are not unique identifiers. Explained very well in this lecture:

https://www.chem.uwec.edu/chem455_s05/pages/Manuals/FTIR_of_proteins.pdf

In what I have written I have also not thought much about casein which contains (very simple) proteins - you see two lines. But they do shift when metals are present, there are publications about this.

These proteins can probably be rehydrated, there is no tertiary structure, but they are not so well characterised. Main interest in these proteins is that they cause allergies.

Casein would just act as a filler on the surface. Or maybe also to close the pores as it sticks. I am not sure whether this is good enough to prevent pigments running up the grain lines. It won't look great to have a clot of casein at the end of f-holes.

 

Uguntde, thank you for the .pdf.  This is excellent information.

Various casein based sizes can act as you mention. 

Can casein or hide glue presence within a 300+ year old varnish system actually be identified as such?  You earlier mentioned "You can't detect proteins after a few hundred years because they are gone."  Is there any reliable way of identifying protein origin where significantly damaged protein structures might be involved?

In terms of violin varnish analyses, non invasive techniques are often/almost always required.  This is usually required even where the extraction of micro-sample material has been allowed due to this material understandably often being preserved in epoxy resin.

[Michael_Molnar]

Glue ghosts from hide glue are due to 2 effects. The first is that the glue seals the surface preventing overlying colorants from penetrating and infusing the wood structure. This is important if you stain the wood without removing glue spots. Tsk-tsk.

The second and most important effect is Stokes fluorescence. Hide glue glows, emitting white light from UV and near-UV (blue) radiation. This white fluorescence weakens any colors above or below the spot. Glue ghosts do not glow in reddish light free of UV or blue.

BTW, hide glue is a great UV detector. When I turn off my shop lights and turn on a UV lamp, all the spots and spills of hide glue glow throughout the shop.

 

[Don Noon]

I have also been able to get an effect similar to a glue ghost by using extremely thick oil varnish directly on the wood.  I really think that wetting and penetration are big factors.

[David Burgess]

On 3/15/2022 at 9:28 AM, Don Noon said:

I don't agree with the hypotheses that it's the color of the coating or the index of refraction that is causing the ghosts.

I rather do. Hot hide glue has a much lower index of refraction than many varnishes, and also some other glues. To me, that's why is is almost impossible to get an invisible joint with an adhesive like epoxy, which has a much higher index of refraction than hot hide glue, tending to darken the wood on both sides of the joint.

Glue can also inhibit the depth of penetration of a stain into the wood, or that of a higher refractive index varnish closer to that of the wood, which while somewhat a separate issue, really is not. Lots of things going on simultaneously.

[uguntde]

On 3/16/2022 at 10:42 PM, John Harte said:

Uguntde, thank you for the .pdf.  This is excellent information.

Various casein based sizes can act as you mention. 

Can casein or hide glue presence within a 300+ year old varnish system actually be identified as such?  You earlier mentioned "You can't detect proteins after a few hundred years because they are gone."  Is there any reliable way of identifying protein origin where significantly damaged protein structures might be involved?

In terms of violin varnish analyses, non invasive techniques are often/almost always required.  This is usually required even where the extraction of micro-sample material has been allowed due to this material understandably often being preserved in epoxy resin.

This is a difficult question. How many 300 year old samples have been analysed so far? Probably none beyond a few taken from violins. I don't think anybody knows whether there are intact proteins after 300 years - I personally doubt it.

The test could of course be an IR measurement. If the two bands are there it is potentially still existing protein. I would want to see further proof that these bands are indeed protein and not anything else.

In principle with the right instrument surface analysis is possible and this is non-invasive. This has been done, see attached. The question is how to interpret such data. Looking for these bands is on the verge of coffee ground reading (from a chemist's point if view).

 

 

 

 

 

1-s2.0-S0026265X17306987-main.pdf

[jezzupe]

18 hours ago, Michael_Molnar said:

Glue ghosts from hide glue are due to 2 effects. The first is that the glue seals the surface preventing overlying colorants from penetrating and infusing the wood structure. This is important if you stain the wood without removing glue spots. Tsk-tsk.

The second and most important effect is Stokes fluorescence. Hide glue glows, emitting white light from UV and near-UV (blue) radiation. This white fluorescence weakens any colors above or below the spot. Glue ghosts do not glow in reddish light free of UV or blue.

BTW, hide glue is a great UV detector. When I turn off my shop lights and turn on a UV lamp, all the spots and spills of hide glue glow throughout the shop.

 

Right, it is the primary effect that we are seeing, and to a certain extent is as simple as "two objects can not occupy the same space at the same time" so we have a "Fermion" reality of the space being occupied already by the hide glue matter, thus "displacement" or the inability for the oil to occupy the "space" where the hide glue is and yet at the same time we have the paradox of the "Boson" or photons {light particles /waves} that can occupy, pass through. interact within the matter of each layer or be in the same place at the same time unlike the fermion based matter.

So the hide glue , already occupying a physical dimensional space {the wood grain} displaces/disallows the oil from occupying that space in the wood grain {cups,tubes,crevasses,pools,fissures,plains... which comprise the wood topography} As they are of dissimilar bases and that because they are not re-solveable they will not "physically mix" they shall always remain two separate films occupying two separate spaces, in this case, on top of each other, yet due to the nature of photons, which can occupy and interact within the same space, we get the optical effects of the light passing thru both mediums and because they have dramatically different indexes the light interacts with both layers at the same time and it is this color hue difference {the displacement in the grain} mixed with the refraction differences and florescence  {the light interacting with two different indexes at the same time} that makes us see what we see.

 

[John Harte]

4 hours ago, uguntde said:

This is a difficult question. How many 300 year old samples have been analysed so far? Probably none beyond a few taken from violins. I don't think anybody knows whether there are intact proteins after 300 years - I personally doubt it.

The test could of course be an IR measurement. If the two bands are there it is potentially still existing protein. I would want to see further proof that these bands are indeed protein and not anything else.

In principle with the right instrument surface analysis is possible and this is non-invasive. This has been done, see attached. The question is how to interpret such data. Looking for these bands is on the verge of coffee ground reading (from a chemist's point if view).

1-s2.0-S0026265X17306987-main.pdf 3.67 MB · 1 download

Thank you for your reply.  Again very interesting.

A number of varnish systems dating from this era have been studied.  Most recent studies seem to have been non invasive, the paper you attached to your post being an obvious example.  Micro-sample material is obviously potentially more informative than what is possible in situ, but less commonly available.  Even so, Strad micro-sample material has been studied by the likes of Brandmair, Echard and members of the Arvedi Lab group.

I don't doubt the data presented in the paper that you have attached but find the interpretation of the data related to protein presence presented in the Conclusions section to be somewhat speculative.  The contrast between what the researchers suggest might be involved in the Tuscan Strad varnish system and that presented in one of their later papers is interesting.  See: https://www.sciencedirect.com/science/article/abs/pii/S1386142520309057

It seems that none of the researchers that I mention above have actually found evidence of a discrete protein based film forming layer in Strad micro-sample material.  In contrast, Echard and members of the Arvedi Lab group have both found such in various other varnish systems from broadly the same era.  The above referenced paper includes examples.

There seems to be more to discover, at least in terms of some old varnish systems.  Even in the later paper that I reference, what the researchers mention regarding the nature of the protein presence in the case of Strad remains speculative.