PAINTED OVER however NOT FORGOTTEN: RESTORING lost PAINTINGS WITH RADIATION as well as MATHEMATICS

An intrinsic residential property of paintings, that makes them both wonderful as well as extremely annoying, is the truth that they are physical objects. sometimes they make it through across the ages as fantastic artifacts of their era, however they are likewise susceptible to being lost as well as even destroyed. sometimes this damage is deliberate, such as when a painting is painted over.

Artists reuse canvas all the time — painting over what was already there. sometimes they may be coerced by a client into altering a painting, or eliminating entire aspects from a scene. Fortunately, nowadays we have many techniques, including x-rays as well as infrared radiation, that can analyze paintings to determine not only the structure of what we can see with the naked eye, however likewise that what lies underneath.

In some cases, we can then reconstruct what was previously hidden, returning to physical truth paintings as well as sketches which haven’t seen the light of day for sometimes centuries.

Paintings are like onions

Painting is an additive method, which means that, starting with a blank canvas or other surface, paint is used in one or more layers, which may overlap with other layers. When painting over an existing painting, the new paint has a tendency to be used on top of these existing layers. While this may obscure what was originally there from the human eye, it is possible to non-destructively peel back these layers, as well as analyze them individually.

The primary techniques to do this utilize x-rays as well as infrared. For decades, this meant utilizing either producing an x-ray picture from the entire painting, or illuminating the work with infrared light as well as catching the showed image. While this provides some level of detail that the naked eye cannot see, these techniques cannot differentiate between layers of paint, nor details such as specific kinds of lead-based paints. Newer, more advanced techniques can provide this type of information.

A great overview of these techniques comes from a paper by Stijn Legrand et al. (2014), as published in Heritage Science. utilizing the example of a 15th century triptych (folding three panel altar painting), it is demonstrated exactly how this specific work saw several revisions over the years. These alterations primarily included adding more of the family’s children, as well as moving existing figures around the painting to make space, which covered up the already painted-in background. a few of the female characters’ gowns were made more moderate later as well, presumably after one of the daughters ended up being a nun.

The Moreel Triptych, 1485, H. Memling (Groeninge Museum, Bruges, Belgium). (A) Photograph; (B) the M6 MA-XRF scanning in front of the right panel; (C-E) MA-XRF pictures of part of the left panel, showing Mrs. Moreel as well as her daughters (ca 60×40 cm2); (F) close-up of the right panel, showing W. Moreel as well as his sons (ca 40×40 cm2); (G-H) corresponding MA-XRF images; (I) plan clarifying the shift of the setting of the eldest son; step size: 1 mm in both directions; dwell time: 0.5 s/pixel. (Credit: Stijn Legrand et al., 2014)
This info was gleaned from a macroscopic X-ray fluorescence (MA-XRF) scan, which utilizes X-rays to ionize the material. The radiation that is emitted from the material after being therefore ionized is indicative of which elementary elements, like lead, are present, as well as in which quantities. As each type as well as color of paint is made up out of different mixtures of these elements, this enables us to see hidden layers as a type of ghost picture in spite of MA-XRF not being layer sensitive.

While exceedingly useful, there is a method to likewise get the precise structure of the paints used: macroscopic X-ray diffraction (MA-XDR). instead of tracking the fluorescence utilizing a sensor put behind the painting, this technique puts a sensor at an angle with the front, together with the X-ray source:

Prototype MA-XRD configuration at the university of Antwerp. A) photograph showing the micro-focus X-ray tube source (S), equipped with a double rounded mirror M as well as detector for recording transmission XRD (D1) as well as XRF (D2) data: these elements are positioned close to a painting mounted on a motorized stage; B) MA-XRD as well as C) MA-XRF pictures acquired by scanning a detail of the painting shown in D): scan size: 78×75 mm2, picture step size: 0.5 mm in both directions, Dwell time: 2 s/pixel. Adapted from [Vanmeert F, Janssens K, De Nolf W, Legrand S, Van der Snickt G, Dik J: Scanning Macroscopic X-ray powder diffraction imaging (MA-XRPD): transfer from the synchrotron to the laboratory, submitted]. (Source: Stijn Legrand et al., 2014)Using a combination of XRF as well as XRD, it is potentially to not only make out successive paint layers, however likewise determine the precise chemistry of many of these, enabling for the distinction between the many lead-based pigments utilized over the past centuries. In addition, infrared radiation — near-IR as well as mid-IR in a hyperspectral configuration — is commonly utilized to get extra details that may be missed by the X-ray-based methods.

Peeling Back Layers

But let’s go deeper. What all of the previously mentioned X-ray as well as IR-based techniques have in typical is that they do not differentiate between the private layers of the painting. however just as you can take X-rays of people from several angles, you can likewise utilize Computed Tomography (CT) scans on art.

For a traditional CT scan it is of program necessary that either the scanner or item rotates to ensure that radiographs can be made from as many angles as possible. While this works well for basically round human bodies as well as similar shapes, flat objects like paintings as well as panels of composite materials cannot be scanned in this manner. right here we see that over the past years there’s been a flurry of research study from both the art as well as materials research study fields into methods to adapt traditional CT scans into a type that will work with these flat objects. This gets us to Computed Laminography (CL).

Charles E. wood et al. (2019, PDF) report on two different methods to perform CL on carbon fiber reinforced polymer (CFRP) sections. The goal right here is to find defects in the composite material, such as air bubbles as well as fractures. utilizing both a hexapod as well as robotic arm setup, CL scans were made, complying with both a raster as well as a restricted angle scan pattern (as opposed to the full rotation of CT). The data was then assembled into the computed design utilizing the Simultaneous Iterative Reconstruction method (SIRT) iterative reconstruction algorithm.

The path of the source as well as detector during the scan in theobject’s frame of recommendation xyz. (Source: S.L.Fisher et al., 2019)
While this provided usable results, the imprecise positioning as well as reduced angles introduced artifacts in the final model. S. L. Fisher et al. (2019) recommendation wood et al. in a research study on an approach utilizing CT scanning devices as discovered in laboratories as well as utilizing a single rotation axis for the subject.

This approach seems to get around many of the limitations of both CT as well as many of the CL configurations. By enabling for full rotation of the item being scanned, this enables for essentially the full variety of angles, while simultaneously offering a steady platform without the positional difficulties encountered by wood et al.

Although still just a proof-of-concept study, the approach shown by Fisher et al. shows that there are relatively simple methods to implement CL, without the utilize of costly devices or a challenging scanning setup.

Restoring That Which was Lost

XRR as well as IRR of Dieu n’est pas un saint, in landscape orientation, exposing a truncated female nude (from above the head to the lower breast) beneath the present picture. (Credit: Catherine Defeyt et al., 2018)
Over the years, techniques like these have been utilized by art conservators as well as others to not only comprehend the physical cosmetics of a painting, however likewise the methods used. With CL in particular, it becomes possible to see the clean strokes as well as layering utilized to accomplish specific effects. By utilizing XRD to analyze the specific pigment utilized in an overpainted section, it is possible to even reconstruct the precise color of that section. This was necessary with the reconstruction of La present enchantée by René Magritte (1898–1967), as documented by Catherine Defeyt et al. (2018)

Created in 1927, this painting vanished around 1932. It was understood that Magritte’s monetary circumstance led him to commonly reuse old works. By examining other works by this artist, it was discovered during X-ray as well as IR-based scans that this vanished painting had in truth been cut up as well as utilized for new works.

Reconstructing this work included scanning existing paintings to discover the private pieces, matching this up with a monochrome picture of the work taken before it was cut up as well as utilizing XRF to determine the pigments utilized for the original painting layers. This info was then integrated to reconstruct what the original, full-color painting would have looked like. even though this will not restore the original work, it does provide us an in-depth look at its original appearance.

Keeping It Real

In the world of art, whatever is about authenticity. This becomes rather evident every time a ‘previously unknown’ or ‘assumed lost’ work of some master surfaces as well as the debate about whether it’s truly by this painter begins. An fascinating element of this is whether a reconstructed, physical version of a previously lost copy has anything in typical with the original. With recent reports of for example a lost Picasso being reconstructed utilizing a neural network trained on other works by Picasso, it’s perhaps finest to see these as reproductions.

A few years back the Smithsonian magazine covered the reconstruction of seven lost masterpieces. This effort utilized any type of existing photographic as well as eyewitness evidence together with understanding about the painter’s methods to paint these works anew. even though we understand that these works are as close to the original as possible, we likewise understand that they were not truly painted by Van Gogh, Monet or any type of of the other masters.

Even so, there is a great deal to be stated for having a physical copy of a piece of history that was when presumed to be lost forever, no matter for exactly how long the debate about where the true value of an art piece lies.