FALVEY MEMORIAL LIBRARY

You are exploring: VU > Library > Blogs > Conserving a Giant: Resurrecting Pietro da Cortona's "Triumph of David" > ZAP! Visualizing Pigments with X-Rays

ZAP! Visualizing Pigments with X-Rays

  • Posted by: Kristen Watts
  • Posted Date: October 30, 2013
  • Filed Under: Chemistry
Kristen Watts working on XRF analysis of Triumph of David

Kristen Watts using XRF to analyze The Triumph of David

As The Triumph of David conservation project gains momentum, we, the chemistry team, have been studying the materials used in the painting. Conservation science is considered science in the service of cultural heritage and is a field of study that most science majors don’t even know exists.  Conservation scientists are interested in the chemistry of artistic materials and techniques and how they age in an artwork’s environment.   The proliferation of high-powered analytical instrumentation has made it possible to analyze historical objects with in-depth, non-destructive techniques. Our role in the conservation team is to provide data to conservators that can identify the materials used by the original artists as well as the materials used during subsequent restoration campaigns (a campaign refers to restoration efforts separated by time).  We are also hoping to provide the art historians with technical information that may help with dating and understanding how Pietro da Cortona and his workshop painted this rare, large format, oil-on-canvas painting.  Ultimately, we would like to provide a scientific answer as to why the varnish and the areas of obvious overpaint have darkened and deteriorated so quickly since the most recent restoration campaign in 1956. At this moment, we are busy trying to identify the pigments present in the painting as well as which paint layers are original and which are restoration.

Inorganic pigments, like verdigris or vermillion, can often be identified utilizing x-ray fluorescence (XRF) and scanning electron microscopy paired with energy dispersive x-ray analysis (SEM-EDX). During the past few weeks, we have been focusing our work on XRF as well as optical microscopy of cross-sections that have been taken, but today we are going to focus on some of our XRF results.

Schematic of XRF process

XRF is incredibly useful in conservation science not only because it’s nondestructive but also because portable, hand-held instruments are available, meaning that the instrument can be brought to the painting instead of bringing the painting to the lab where the instrument resides. XRF utilizes high energy X-rays to eject inner shell electrons from an element. The outer shell electrons will then fill the electron hole, releasing an x-ray photon in the process. This photon release is known as fluorescence and the particular energy of the released photon is specific to each element. Because of this specificity, we can use XRF to help us identify inorganic pigments in areas of interest. (For a more in depth look at the XRF mechanism of action, see here)

 

XRF spectra of the yellow shirt and the red toga on the soldier.

XRF spectra of the yellow shirt and the red robe on the soldier.

In the case of the soldier’s red robe (as seen in the photo at the left) we found a signal for mercury (Hg), indicating that the red color is probably due to a vermillion (mercury sulfide) pigment. There was also a large signal for lead (Pb) but this signal is found throughout the painting as it is caused by a lead white containing ground layer. His yellow shirt, on the other hand, showed signs of chromium(Cr) and barium (Ba) which would indicate a more modern chrome yellow (post 1800) or lemon yellow (post 1830) paint, thereby indicating that one of the paint layers originates from a more modern restoration campaign.

 

 

 

As mentioned previously in the Metigo map blog post, there are a lot of areas with heavy overpaint present as well as several restoration campaigns. By using XRF to monitor the presence of zinc (Zn), we can assist the conservators in tracking the removal of the restoration materials. Currently, zinc is suspected to be a component of the varnish or in a slightly pigmented glaze from a previous restoration. We suspect this because we see zinc disappear significantly with varnish removal, as seen in the image below, comparing the uncleaned overpaint (red), cleaned but still overpaint (green), and cleaned without overpaint (pink) all on a soldier’s leg in the painting. The spectrum corresponding to the uncleaned overpaint shows a moderate zinc signal, whereas zinc is not detected in the spectrum corresponding to an area of overpaint with just the varnish removed and the spectrum corresponding to a completely cleaned area.

 

Comparison of uncleaned overpaint, cleaned overpaint, and totally cleaned areas present in a soldier's leg

Comparison of uncleaned overpaint (red line), cleaned overpaint (green line), and totally cleaned (pink line) areas present in a soldier’s leg

 

Because XRF simultaneously examines all the layers of the painting from the ground, paint layers, over-painted layers, and varnish, we can’t tell exactly in which layer the pigment is present by XRF alone. However, this XRF data is useful when determining where to micro-sample the painting to get layer-specific pigment information through techniques such as SEM-EDX and fluorescence microscopy, which you can read about in later posts. We are just beginning to unravel some of the mysteries surrounding this painting and our team is learning more every day.

Until next time, Ciao!

Anthony, Amanda, and Kristen.

16 Comments »

  1. Pingback by Peeling Back the Layers | — December 2, 2013 @ 5:43 pm

    […] working on identifying pigments and binding materials used in The Triumph of David. As mentioned last time, X-ray Fluorescence [XRF] is a technique that allows us to get a broad overview of what inorganic […]

  2. Pingback by Peeling Back the Layers | — December 6, 2013 @ 11:10 am

    […] month sampling and preparing cross-sections for analysis from The Triumph of David. As mentioned last time, x-ray fluorescence (XRF) is a technique that allows us to get a broad overview of what inorganic […]

  3. I know this website gives quhality dependent articles or reviews aand extra information, is there
    any other web sote which provides these data in quality?

    my website :: best garcinia cambogia product on the market

  4. Comment by Cape Coral Web Design — July 15, 2014 @ 10:51 pm

    I needed to thank you for this excellent read!! I definitely loved every little bit of it.

    I have got you bookmarked to check out new stuff you post…

  5. Comment by best friend quotes — August 3, 2014 @ 6:11 pm

    Hi there, yeah this paragraph is in fact fastidious and I
    have learned lot of things from it about blogging.
    thanks.

  6. Comment by movie Reviews — August 4, 2014 @ 5:17 am

    I have read so many posts about the blogger lovers but this article is genuinely a
    pleasant article, keep it up.

    my homepage … movie Reviews

  7. Comment by natural garcinia turbo trim plus — August 6, 2014 @ 5:10 pm

    Awesome post.

    Feel free to surf to my webpage – natural garcinia turbo trim plus

  8. Comment by Garnicia cambogia select Review — August 7, 2014 @ 8:57 am

    It’s difficult to find educated people in this particular subject, but you seem like you
    know what you’re talking about! Thanks

    Here is my page: Garnicia cambogia select Review

  9. Comment by download games — August 7, 2014 @ 1:56 pm

    I hardly comment, but i did some searching and wound up
    here ZAP! Visualizing Pigments with X-Rays |. And I actually do have some questions for you if it’s allright.

    Could it be only me or does it give the impression like a
    few of these remarks come across like they are written by brain dead individuals?

    :-P And, if you are posting at other sites, I’d like to follow anything fresh you have to
    post. Could you list of all of all your public sites
    like your Facebook page, twitter feed, or linkedin profile?

    Here is my blog – download games

  10. Comment by lovely — August 13, 2014 @ 12:53 pm

    I’m not that much of a online reader to be honest
    but your sites really nice, keep it up! I’ll go ahead and bookmark your website to come
    back later. Many thanks

  11. Comment by video games for kids — August 14, 2014 @ 8:56 am

    Hi superb blog! Does running a blog similar to this require a large amount of
    work? I have no expertise in coding however I had been hoping to start my own blog soon. Anyway, should you have any suggestions or techniques for new blog owners please share.

    I understand this is off subject however I just wanted to ask.
    Appreciate it!

  12. Comment by afs — August 21, 2014 @ 10:00 pm

    The earth of Mafia Wars has virtually blossomed into a massive platform in which millions of people from unique nations play the game
    every day. These types of hints can generally be obtained
    from sites like Geocheating. There is nothing that one
    can do to stop these gamers from using the World of Warcraft Cheats.

  13. Comment by cheap E-Liquid — August 23, 2014 @ 3:17 am

    Hey there I am so thrilled I found your blog page, I really found you by mistake, while I
    was researching on Digg for something else, Regardless I am here now and would just like to say thanks for a incredible post and a all round enjoyable
    blog (I also love the theme/design), I don’t have time to read
    it all at the minute but I have bookmarked it and also added
    in your RSS feeds, so when I have time I will be back
    to read a great deal more, Please do keep up the excellent b.

  14. Comment by Social Wars Facebook Hack — August 23, 2014 @ 8:38 am

    What is the best way to find websites you are enthusiastic about?

    Quite simply, how do you seek out blogs that suit
    what I do want to read about? Does anyone know how to BROWSE by subject through blogs or whatever on blogger?.

  15. Comment by Fashion IQ - Masha Lopatova — August 24, 2014 @ 6:10 am

    This post gives clear idea in support of the new visitors of blogging, that really how to
    do running a blog.

    Feel free to surf to my page … Fashion IQ – Masha Lopatova

  16. Comment by temple run game — August 28, 2014 @ 5:37 am

    Hello colleagues, how is the whole thing, and what you want to say on the topic
    of this paragraph, in my view its truly amazing in favor of me.

RSS feed for comments on this post. TrackBack URI

Leave a comment


6 − three =

 


Last Modified: October 30, 2013