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A Solution to Fill the Voids

Today's guest blogger is Sarah Gowen, the Samuel H. Kress Fellow in Paintings Conservation.

As many of the previous conservation blog postings have illustrated, conservators are often faced with challenges in the analysis and treatment of artworks; however, sometimes the examination of a work can be in itself a challenge.  When a work enters the IMA conservation studio, it is carefully examined and documented.  Documentation includes reporting observations about the object’s condition and detailed photography of all surfaces.  During this process, x-ray images may be taken.  X-radiographs can augment the conservator’s understanding of the object’s condition, reveal the artist’s technique, and expose artist changes.

Unfortunately, sometimes the process is not as easy as taking a quick x-ray image of a work.  What happens when the image in question is obscured by another element of the work itself?  Take for example cradled panel paintings.  In the past, treatment of wooden panel paintings often included adhering a criss-crossed network of wooden beams to the reverse to support the panel.  Conservators now know that restraining wood in such a way can cause additional damage, but the process of removing a cradle can be invasive and is often not necessary if the painting is kept in a stable environment.  The network of beams, however, complicates x-radiography.

A case in point is this small (11 1/4 in. x 8 5/8 in.) Dutch portrait by Ferdinand Bol from 1659.  A cradle has been adhered to the reverse, likely to support two horizontal damages (one towards the top through the sitter’s hat and one at the bottom below the sitter’s hand).

Comparison

Front and back of Portrait of a Man by Ferdinand Bol

The resulting x-ray image looks like this:

 

Initial x-ray image of Portrait of a Man by Ferdinand Bol

Initial x-ray image of Portrait of a Man by Ferdinand Bol

During x-radiography, x-rays penetrate through the object and expose a film.  Materials of greater density block the x-rays and appear whiter in the image.  In this case, the cradle adds an extra thickness in those areas and obscures the image of the paint layer.  It is apparent that the artist changed the position of the sitter’s hand, but overall the image is difficult to read.  Digital adjustment of such images can be difficult and time consuming, leading conservators to seek materials that can be used to compensate for the voids in the cradle.  For example, Scott Heffley (Conservator of Paintings at the Nelson-Atkins Museum of Art) developed a putty material made of wax, mineral oil, and glass microbubbles that can be gently pressed into the cradle cavities.

The most successful solution for this project was to lightly pour an inert synthetic resin powder on the reverse of the painting.  To do this, a supportive collar was made around the work to keep the powder confined, and the setup was placed on top of the x-ray film.  Resin powder was placed over the painting reverse until it covered all surfaces of the cradle.  After taking the x-radiograph, the powder was vacuumed from the painting reverse.

Applying resin powder to the panel reverse

Applying resin powder to the panel reverse

The resin mimics the density of the wood.  The resulting x-ray is much easier to read, as the surface has a more homogeneous exposure.

Final x-ray image of Portrait of a Man by Ferdinand Bol

Final x-ray image of Portrait of a Man by Ferdinand Bol

In this x-radiograph, artist changes are more apparent.  The most visible are outlined in the following image:

 

Final x-ray image with areas of interest defined

Final x-ray image with areas of interest defined

  • The green dashed lines delineate the sitter’s hat and shoulder, which are not fully visible in the x-ray image.
  • The red line shows the original position of the sitter’s hand.
  • The yellow lines define areas that do not appear to relate to the final image; for example, the outlined area underneath the sitter’s nose resembles a lacey collar, possibly suggesting that another figure was originally painted.
  • The white lines define areas that appear dark in the x-radiograph; however, it is not clear if they relate to the current image, are remnants of a previous image, or are simply the result of irregularities within the panel.

While it may not be possible to use this method in all cases (such as for paintings that are much larger or cannot be placed face down), the use of resin powder was a successful solution to this x-radiography challenge.

Sarah’s work is supported by funding from the Samuel H. Kress Foundation, administered by the Foundation of the American Institute for Conservation

Filed under: Art, Conservation, Guest Bloggers

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