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

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

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

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

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

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.

Attached Thumbnails

 

Danger

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

zoobyshoe

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

Tell your friends!

Danger

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.