X-ray use on fine art wood panels

[zeeman]

Warm greetings from a first time poster,

Thank you for looking. I hope I posted in the correct category and apologize if I did not. My question revolves around a late 19th century painting on wood panel made of cypress with oak strapping (2.6cm thick). I'm having the panel radiographically X-rayed to produce an image of the under drawing. I would like to know if anyone here has experience with this type of work. Specifically I would like to know what kVp and mAs settings you would use and for what duration? Any thoughts would be greatly appreciated.

 

[lisab]

Can you get some samples of the wood species to experiment with? I realize it won't be the original old wood, but it should be pretty close wrt how x-rays pass through it.

 

[lisab]

Oh and welcome to PF !

 

[Tsu]

Warm greetings from a first time poster,

Thank you for looking. I hope I posted in the correct category and apologize if I did not. My question revolves around a late 19th century painting on wood panel made of cypress with oak strapping (2.6cm thick). I'm having the panel radiographically X-rayed to produce an image of the under drawing. I would like to know if anyone here has experience with this type of work. Specifically I would like to know what kVp and mAs settings you would use and for what duration? Any thoughts would be greatly appreciated.

Are you using a film/screen combination or digital radiography? The mAs includes your duration (mA x time in sec.). I typically shoot a 3cm wrist at about 72 kv and 1.5mas at a 40 inch distance using a digital system (so higher kv can be used). Cypress is usually considered a soft wood so try that technique and adjust as needed. If you are using a film/screen combo or you want more contrast to see the wood grain better, use lower kv and more mas. ie. 60kv at 3mas. Hope this helps.

 

[AlephZero]

I can't give you any advice on the machine settings, but I know somebody who builds and restores old musical instruments (harpsichords and such like) who has an arrangement with a local vet to "borrow" their Xray machine to ckeck out the internal structure of old instruments before trying to take them apart. Consdiering a full size harpsichord is about 8 feet long by 3 feet wide, an Xray machine designed to deal with a horse or cow is about the right size for the job!

AFAIK this is fairly routine technique in the art world now. I saw this link today: http://www.bbc.co.uk/news/entertainment-arts-17449469

 

[zeeman]

Thank you all so much.
lisab, I've been told that extracting even a minute sample can lower the potential value of the work. I'm not sure it is true but it has made me cautious about sample extraction.
Tsu, I am going to use a film/screen combo. Many thanks for your post.
AlephZero, Thank you for the link.

Thank you all for helping to make my first experience here a true joy. My best wishes to all.

 

[Danger]

This will probably seem like a silly question, but wouldn't varying amounts of lead in the pigments cause inconsistent exposure across the painting?

 

[Tsu]

This will probably seem like a silly question, but wouldn't varying amounts of lead in the pigments cause inconsistent exposure across the painting?

Not silly at all. Yes it will cause inconsistant exposure. That's the beauty of it. Just like regular xrays where you see skin, bone, air, and even muscle shadows. I'm curious about what you are looking for or at, zeeman.

 

[M Quack]

lisab, I've been told that extracting even a minute sample can lower the potential value of the work. I'm not sure it is true but it has made me cautious about sample extraction.

Do not extract a sample from the original art work. Make a mock-up using the same woods and layer thicknesses (or as close as you can get) and just paint on a few lines using paints typical for the time.

In any case, the damage the x-rays will do to the painting and support will be pretty minimal. It is dead, so it cannot develop cancer. And the doses needed to produce burns or notable degradation of organic substances like binders are much much higher.

This type of work does seem to be pretty standard these days, so you should be able to find exposure values in papers describing similar work. In case of doubt, contact the corresponding author.

 

[zoobyshoe]

I'm curious about what you are looking for or at, zeeman.

He/she wants to see the under drawing, which is whatever preparatory sketch the artist made on the panel to guide the painting. Depending on the artist, this could be anything from very minimal to very elaborate. It can be of interest for many reasons. If an artist's under drawing technique is well known it can help authenticate a painting as by a given artist. If the attribution is not in question, this might be the first time their underdrawing technique is being explored, and would be of interest just to know how they worked. It's a hallmark of Caravaggio, for instance, that he made no under drawing at all, that he just gouged a few compositional lines into the wet primer and composed the whole painting for the first time then and there. Other interesting things would include "pentimento", where the artist veered away from the under drawing, having changed his mind once the painting got underway, or that he repainted already finished sections not being satisfied with the placement of one thing or another. The biggest surprise is finding there's a whole different painting underneath when the artist has recycled an old canvas by just painting over a previous work.

 

[Danger]

Not silly at all. Yes it will cause inconsistant exposure. That's the beauty of it. Just like regular xrays where you see skin, bone, air, and even muscle shadows. I'm curious about what you are looking for or at, zeeman.

Hmmm... it just seems to be a complication as opposed to a "beauty". It would be great for creating a "false-colour" image, but that seems a bit irrelevant since you can see the original colours without it. The only instance in which I can think of it being beneficial is if you are trying to see an old painting under a new one. If the new one contains no lead, then it would be great.
In this case, though, the overlying paint probably does contain lead, given its age, but the sketch beneath likely has none.
This is confusing.

 

[zeeman]

zoobyshoe is correct. X-ray is being used for authentication work. The painting is likely a "fully realized study" of a monumental work completed later by the artist. I've included a photo of another work by this artist in which he is preparing to tranfer the small work to a large format. The measurement lines on the side of the preparatory work are what I am looking for on my panel.

 

[Danger]

Cool. So is this thing actually medieval, or is it a retrospective from a more modern artist?

 

[zoobyshoe]

Cool. So is this thing actually medieval, or is it a retrospective from a more modern artist?

As he says in the OP, it's late 19th century painting.

 

[zeeman]

The drawing is Prince Vladimir the Great by Victor Vasnetsov (Russian 1848-1926) from around 1890.

I am also curious, does anyone know what gold leaf will appear like under X-ray?

Again I wish to state my appreciation to the forum members. Hands down Physics Forums is the BEST site on the web!

 

[lisab]

The drawing is Prince Vladimir the Great by Victor Vasnetsov (Russian 1848-1926) from around 1890.

Again I wish to state my appreciation to the forum members. Hands down Physics Forums is the BEST site on the web!

Tell your friends!

 

[Danger]

As he says in the OP, it's late 19th century painting.

I didn't express my question well, and I appreciate that you pointed it out. What I meant was whether the image is historically accurate or a romanticism of the olden days.

 

[M Quack]

Gold is a heavy atom that absorbs a lot of x-rays. Gold leaf, on the other hand, is very very thin. I think you are bound to see all the cracks, gaps and folds where the thickness of the gold leaf varies.

If lead oxide was used as white, that also absorbs x-rays strongly because of the lead.

 

[Andre]

Maybe these specialists can help

A painting dismissed for years as the work of an unknown artist has been identified as a piece by Vincent Van Gogh, after x-rays revealed an image of two wrestlers fighting underneath the floral still life...

courtesy Nilequeen for finding this.

 

[zeeman]

Vasnetsov did paint romantisized figures from both Russian folklore and history. Most of his famous work falls in the categories of social realism or art nouveau. The info on gold leaf and the link above are greatly appreciated. Thank you.

 

[zoobyshoe]

In 1882, Vasnetsov received a commission to produce a decorative panel for the rotunda of the Historical Museum in Moscow, which was his first big monumental project. Yet the most significant and time-consuming work of this type was the decoration of the Cathedral of St. Vladimir in Kiev, which Vasnetsov began in the autumn of 1885 at the invitation of the art historian Adrian Prakhov, who supervised the construction of the cathedral. Vasnetsov jumped at this offer as it gave him the opportunity to create an integral ensemble comparable to those done by ancient fresco-painters. Work on the decoration of the cathedral took over 10 years, during which Vasnetsov executed nearly 400 sketches and studies. The murals he painted with his assistants covered almost two thousand square meters. Fulfilling this assignment Vasnetsov relied on his favorite range of motifs and characters, painting the walls with the images of princes Vladimir, Alexander Nevsky, Andrey Bogoliubsky, Princess Olga, the chronicler Nestor, and other outstanding figures from Russian history.

http://www.cozy-corner.com/art/art_painters_vaznetsov.htm

There are quite a few of his works if you google images and his name.

 

[Tsu]

Thank you all so much.
lisab, I've been told that extracting even a minute sample can lower the potential value of the work. I'm not sure it is true but it has made me cautious about sample extraction.
Tsu, I am going to use a film/screen combo. Many thanks for your post.
AlephZero, Thank you for the link.

Thank you all for helping to make my first experience here a true joy. My best wishes to all.

This is very interesting. Do you know the speed of your film and/or the type of screens you are using. I would suspect the gold leafing will be barely visible at the techniques you will be using. You mentioned an oak 'strapping;? Que eso?

 

[Danger]

You mentioned an oak 'strapping;? Que eso?

Good point. Knowing nothing of art, I automatically took an engineering approach to that term and assumed a support lattice affixed to the backside of the frame. Whatever it is, it can't be very flexible if made of oak; that stuff is more durable than steel in some instances. (I know that it can be bent when steamed, but not normally. In my locksmithing days, we charged the same for an installation in an oak door as we did for a metal one. It wears out the tools just as quickly and takes as much elbow grease.)

 

[zoobyshoe]

Good point. Knowing nothing of art, I automatically took an engineering approach to that term and assumed a support lattice affixed to the backside of the frame. Whatever it is, it can't be very flexible if made of oak; that stuff is more durable than steel in some instances. (I know that it can be bent when steamed, but not normally. In my locksmithing days, we charged the same for an installation in an oak door as we did for a metal one. It wears out the tools just as quickly and takes as much elbow grease.)

You're probably right that the oak "strapping" is some sort of support to add strength but I can't say for sure exactly how it's employed. Painting on wood panels in the late 19th century would represent a throwback to earlier times. Everyone had already long since converted to painting on canvas:

Early works were still panel paintings on wood, but around the end of the 15th century canvas became more popular, as it was cheaper, easier to transport, and allowed larger works. Venice, where sail-canvas was easily available, led the move.

http://en.wikipedia.org/wiki/Oil_painting

Vasnetsov, though, being Russian, might have been imitating the wood panels of the ubiquitous Russian Icon for these smaller "sketches". If you go here:

http://en.wikipedia.org/wiki/Russian_icons

and scroll down to the section "Iconography techniques and collecting" you'll see a photo of the back of a wooden icon which shows two horizontal braces or "back slats". The OP might be referring to something like these when speaking of "strapping".

Panels that utilize what are known as "back slats" — cross members that are dovetailed into the back of the boards that make up the panel to prevent warping during the drying process and to ensure structural integrity over time — are usually older than 1880/1890. Subsequent to 1880/1890, advances in materials negated the need for these cross members, thus, are seen either on icons painted after this time period when the intent of the artist was to deceive by creating an "older looking" icon, or on icons which are rendered according to traditional means as a way of honoring the old processes. Back slats are sometimes necessary on newer icons of large size for the same reasons (warping and stability) as existed pre-1900.

 

[Tsu]

Will the strapping remain in place for the xrays? If so, its a hard wood, so more kv will be needed for more penetration.

 

[Danger]

Will the strapping remain in place for the xrays? If so, its a hard wood, so more kv will be needed for more penetration.

This is vaguely reminiscent of the time that my ex- refused to remove her underwire bra for a mammogram...

 

[Tsu]

This is vaguely reminiscent of the time that my ex- refused to remove her underwire bra for a mammogram...

Oh god *wiping tears from eyes*...I miss u danger!

 

[Danger]

Oh god *wiping tears from eyes*...I miss u danger!

If you think that it's weird now, you should have seen it then. I honestly thought that I was seeing blueprints of the Hindenburg, and couldn't figure out why it was double-exposed.