Advances in Digital Radioscopy for Use in Historic Preservation (2007-05)

In the interest of saving as much historic fabric as possible and not altering or scarring historic materials as a result of investigative probes, architectural conservators look to nondestructive testing methods for the evaluation and identification of materials, conditions and alterations made to structures over time. As the answers to these and many other questions are typically concealed in a historic structure, nondestructive techniques of investigation are a necessity, but few are available. Digital radioscopy is one of those techniques.

The goal of this work was to advance the use of digital radioscopy for assessing wood in historic structures. The work focused on:

• Investigating historic fabric and construction details using stereo-radioscopy
• Evaluating the extent of wood deterioration using digital imaging techniques
• Investigating licensing and regulatory requirements for use of portable x-ray equipment
• Investigating safety measures needed to operate the equipment in historic structures

In distilling the findings related to post-processing of digital radiographs, three main points are relevant. First, digital imaging affords the field operator the opportunity to modify image capture techniques based on real-time or near real- time (i.e., field processing) image production. This is particularly important in building investigation where conditions are variable, and future access may be difficult.

Second, the availability of relatively inexpensive mass-market (e.g., Adobe® Photoshop®) and multi-market specialty software (e.g., Photoflair®, Photomodeler) raise the possibility that software applications can be found and tweaked so as to extend the power of digital radioscopy for building investigation without a prohibitively large outlay of research and development (R&D) resources.

Finally, while the intuitively legible graphic (i.e., pictorial) output of radiographic investigation can provide convincing information, the efficient investigator must weigh whether increasing data inputs is worth the investment, and under what circumstances interpretive experience, multi-method data corroboration, and tacit knowledge suffice.

As demonstrated in this project, the potential that real-time digital radioscopy investigation presents is exciting and could have great positive impact in the field of historic preservation. Practical use can be found in some of the following areas:

• Historic structures reports.
• Documentation of original construction details
  • Documentation of the chronology of construction of a historic structure,
  • Documentation of material dimensions,
  • Documentation of tool markings,
  • Documentation of fastener shapes and sizes.
• Identification of the alteration of such details due to modifications.
• Structural evaluation of conditions and construction details.

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