PMG Examination and Documentation

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In progress: Seeking additional comments and images to develop this section


Date initiated: September 2009
Contributors: Luisa Casella, Jiuan-jiuan Chen, Dan Kushel, Paul Messier, Jennifer McGlinchey Sexton, Amanda Maloney

The Photographic Materials Conservation Catalog is produced by the Photographic Materials Group of the American Institute for Conservation of Historic and Artistic Works as a convenience for the membership. The treatments, methods, or techniques described herein are provided for informational purposes. The reader assumes responsibility for any application results.

Purpose of Examination and Documentation

Examination and Documentation are part of the process of conservation of an object for documenting condition (before, during and after treatment) as well as tools for assessment. Standardized documentation and examination techniques are used by conservators as part of their practice in accordance with AIC's Code of Ethics that states in article VII: "The Conservation Professional shall document examination, scientific investigation and treatment by creating permanent records and reports".
Documentation techniques have to follow strict rules of consistency and accuracy.
Visual documentation must be accompanied by written reports (examination, treatment log and treatment report) that include information on the purpose of examination, authorship and date.
Visual documentation must include distinctive object information:

  • Owner/custodian
  • Maker/origin
  • Subject/title/ scientific classification
  • Measurements
  • Marks/ labels/ prominent features
  • Date of creation

The extent of detail in report information has to be thought through in relation to the purpose of the conservator’s specific intervention. The conservator must have a practice of elaborating an examination report with a treatment proposal; maintain a treatment log with detailed information on procedures and materials used, including photographic documentation; and write a treatment report with after treatment images.

Standards, Guidelines and Recommendations

  • Visual documentation must include:
    • object identification
    • measurement scale
    • color and gray scales
    • light angle and direction indicator
  • AIC produces PhotoDocumentation targets that include all of these.
  • It is part of the conservator’s responsibility to preserve records produced in the course of examination and treatment of objects. It is therefore part of conservation practice the insurance of using permanent hardcopy materials, maintain backups of digital information, and preservation of these records. Appropriate metadata should be included in the digital file (this is becoming less of an issue as software now includes most of the technical information relevant to a file). File naming should also be explicit.
  • General photodocumentation recommendations:
    • List what to photograph prior, reducing object handling
    • Make sure you have time – great damage can happen to objects at this stage
    • Never put the object in danger in the studio – insure no documentation tools risk falling onto the object
    • Use the optimal lighting situation during documentation to observe details of the object you may have missed
    • Record lighting and camera height and setup to repeat in AT documentation

Equipment and Materials: Considerations


Examination and Documentation Techniques for Photographic Materials

Visible light examination and photography

  • General illumination sources,color temperature and spectral characteristics, filtration
    • The first requirement for accuracy in photographic documentation is ensuring a correct reproduction of color. In digital cameras this is done by calibrating all hardware components (camera and monitor), as well as by performing white balancing prior to each session, using an 18% graycard.
    • It is good practice to photograph a color chart such as the Gretag-Macbeth ColorChecker, and measure the RGB values on the camera software (white should be around 245; grey around 160; black around 53).
    • When documenting objects one must keep record of the position of the light source in order to repeat the setup when document during and after treatment images. Light sources can be halogen lamps or calibrated fluorescent light boxes.
  • Different illumination techniques allow to record different aspects of the object:
    • Normal illumination - provides a homogenous lighting of the object similar to a normal display situation. In a documentation setup it implies having two light sources positioned at 45 degrees towards the object. It allows observing the image, paper tint, toning, and condition. It is achieved by using two projectors equidistant to the object at a 45 degree angle towards the surface. If the projector light is too harsh causing shadows that can alter the perception of the object, diffusers can be placed in front of the light source to soften the light (these can be achieved with any translucent material such as paper tissue).
    • Raking illumination - lights the object from an angle (using one light source) and allows observing planar distortion.
    • Specular illumination - uses a light source at a parallel angle directly at the object surface (commonly by reflection from a white material or by tilting the object towards the light source). It allows observing surface texture and sheen; surface damage such as abrasion, cracking,or silver mirroring.
    • Axial specular - allows recording the negative view of daguerreotypes. This is achieved by placing a glass at a 45° angle over the object (see http://media.wix.com/ugd/750e25_f0d566fcebe84c7988dcf252c6ddd190.pdf).
    • Transmitted - uses a light source placed beneath the object. For certain objects on transparent supports, transmitted light may be the best way to document the image content and other techniques may be best to highlight condition issues such as cockling or breakage. Transmitted light can also be useful for documenting condition issues with objects such as ambrotypes where it can highlight a reticulated backing or a colored glass support.
    • Polarized - uses filters on the light sources and camera lens to allow photography of light waves from a specific direction only. This facilitates clear capture of image content from glossy/reflective photographic objects or objects with silver mirroring.
    • Monochromatic.
  • Digital photography: resolution; use of digital camera; file format; exposure and contrast control; color control; file storage and backup.
  • Close-up photography, photomicrography, and photomicrography.
  • Use of the stereomicroscope
  • Photography of 3-D objects

Non-visible Radiation examination

Ultraviolet (UV) examination concepts and techniques

  • UV examination can help document condition issues that may not be otherwise visible:
    • The absence, presence, local fading or transfer of optical brighteners
    • Evidence of mold growth, adhesives, varnishes, or retouching
  • Visible fluorescence with UVA and UVC excitation
    • General considerations for documentation
      • Like normal light photography, cameras, radiation sources, filtration and post processing should be calibrated.
      • Most DSLR cameras can be used to capture UV/visible fluorescence with minimal additional equipment or modification required.
      • Use care when using UV radiation sources. This type of radiation is damaging to the human eye, skin, as well as photographs and objects. Avoid unnecessary exposure and wear UV filtering safety goggles.
      • UV fluorescence is an emissive light source. This differs from typical conservation documentation which captures reflected light. For this reason, users may encounter unique issues with intensity, color rendering and exposure.
      • The documentation area must be completely dark to successfully capture UV/visible fluorescence. Working with a task lamp and adjusting the brightness on your monitor can help the user's eyes adjust to this environment.
      • Check the documentation area for fluorescent materials. Many common backing materials, like papers and fabrics, have a small amount of fluorescence that can interfere with images. Cover or remove all fluorescent materials in the documentation area.
      • Use two radiation sources to irradiate the object evenly. Using only one lamp can cause uneven fluorescence.
      • Filters are needed to ensure that only visible fluorescence (400-700nm) passes to the camera sensor/film.
        • UV filtration: most common is the Wratten 2e (transmits 420nm and higher). This filter also limits some of the blue light that is commonly emitted by UVA lamps.
        • IR filtration: PECA 918 (transmits 350nm-700nm)
        • In-camera filtration: digital cameras contain proprietary internal filtration to reduce IR leakage and the transmission of visible light between 600 and 700nm. These filters are often called "hot mirrors" by manufacturers. One type of in-camera filtration is the BG-38, but actual filtration can vary with manufacturer, brand and year. These filters mimic the sensitivity of the human eye. Users of modified cameras should purchase on-camera filters to capture UV/visible images.
        • Improper filtration can cause color casts in the image. A magenta color cast can be caused by leakage of UV and/or IR. Cameras can vary considerably on their sensitivity to UV and IR, so test your camera if you are unsure how much filtration is needed.
    • Longwave - UVA (320-400nm)
      • Common Radiation sources
        • High Pressure Mercury: Commonly used as inspection lamps. These lamps require long warm up times but emit a large amount of UVA output. Main emission peak is 365nm.
        • Low Pressure Mercury: Commonly used for documentation and inspection. These lamps are fluorescent tubes commonly known as "black lights". Main emission peak is between 360-370nm. Low pressure mercury lamps require much shorter startup times (~5 minutes), but emit less UVA radiation than high pressure sources.
        • LED: can be targeted to any range. Use care when selecting LED UVA lamps, as the emission may not be ideal for UV/visible documentation.
      • Standardization
        • Fluorescence standards are currently being developed for UVA/visible fluorescence. This standard will allow users to calibrate their camera, set white balance, and set exposure. See www.uvinnovations.com for more information.
        • Professional guidelines and standardization of filtration, radiation sources and post processing can help produce more consistent images across institutions, users and equipment.
    • Shortwave - UVC (185-280nm)
  • Reflectance/absorbance of UVA and UVC

Infrared (IR) techniques using film and vidicon imager

  • Reflected and transmitted IR
  • IR luminescence
  • False color IR

Radiographic (XR) techniques

  • Grenz (low kV) direct exposure
  • Standard direct exposure
  • Electron emission radiography
  • Electron transmission radiography of paper artifacts
  • Beta radiography of paper artifacts


References

Infrared Examination and Photography

  • Andrew, Sally R., and Dinah Eastop, "Using Ultra-violet and Infra-red Techniques in Examination and Documentation of Historic Textiles," The Conservator, No. 18, 1994, pp. 36, 50 - 56.
  • Eastman Kodak, Applied Infrared Photography, Publication #M-28,Rochester: Eastman Kodak, 1968., 1972, 1977, last printing 1987. Reprinted 1995Rochester: Pixel Press.
  • Gibson, H. Lou, Photography by Infrared: Its Principles and Applications, New York: John Wiley & Sons, 1978. (Third Edition of Photography by Infrared by Walter Clark.)
  • Kushel, D.A., "Applications of Transmitted Infrared Radiation to the Examination of Artifacts", Studies in Conservation, vol. 30, no. 1,February 1985, pp. 1-10.
  • Williams, Robin, and Gigi Williams, Medical and Scientific Photography: An Online Resource for Doctors, Scientists and Students, http://msp.rmit.edu.au/

Infrared Luminescence

  • Bridgman, C.F., and H.L. Gibson, "Infra-red Luminescence in the Photographic Examination of Paintings and Other Art Objects", Studies in Conservation, vol. 8, 1963, pp.77-83.

False Color Infrared

  • Kecskeméti, Istvan, and Mika Seppälä, “False-colour Infrared (FCIR) Imaging: An Inexpensive Method for Identifying Iron-gall Ink by Standard Digital Camera,” PapierRestaurierung,Vol. 7, no. 1, 2006, pp 18 - 23.

IR Electronic Imaging Cameras

  • Delaney, J.K., and C. Metzger, E. Walmsley, and C. Fletcher, "Examination of the Visibility of Underdrawing Lines as a Function of Wavelength;" Preprints, ICOM Committee for Conservation 10th Triennial Meeting, Washington DC, USA, 1993, pp 15-19.
  • Walmsley, Elizabeth, Colin Fletcher, and John Delaney, "Evaluation ofSystem Performance of Near-infrared Imaging Devices" Studies in Conservation, vol. 37, no. 2, May 1992, pp 120-131. [See also "Improved Infrared Imaging Systems" in AIC News, January 1993, p.20.]

IR Image Processing

  • Cupitt, John, Kirk Martinez, and Joe Padfield, VIPS (Vasari Image Processing System) a free downloadable software system designed for handling large image files, and doing composite images, a joint project of the National Gallery and University of Southampton, UK, available at http://www.vips.ecs.soton.ac.uk/index.php

Thermography

  • Stanton,Moyna,, “Pollaiuolo: Finding the Pieces of the Puzzle,” in Battle of the Nudes: Pollaiuolo’s Renaissance Masterpiece, Cleveland Museum of Art website: http://www.clevelandart.org/exhibcef/battle/html/index.html.*Garland,Kathleen, Paul Benson, L.D. Favro, Xiaoyan Han, and Jianping Lu, “Preliminary Evaluation of Infrared Thermography for Monitoring the Consolidation of Voids and Delamination on Stone Artifacts in Real Time,” Art ‘O5 – 8thInternational Conference on Non-destructive Investigations and Microanalysis for the Diagnostics and Conservation of the Cultural and Environmental Heritage,Lecce, Italy, May 15-19 2005.

Multispectral Imaging

  • Fischer,Christian and Ioanna Kakoulli, “Multispectral and hyperspectral imaging technologies in conservation: current research and potential applications,” Reviews in Conservation, No. 7, 2006, pp 1 –16.

Examination of Drawings on Paper

  • Fletcher, S., "A Preliminary Study of the Use of Infrared Reflectography in the Examination of Works of Art on Paper", Preprints: ICOM-Committee for Conservation 7th Triennial Meeting, Copenhagen, 1984, 84.14.24-28.*Harrison,Wilson r., Suspect Documents: Their Scientific Examination, Chicago:Nelson Hall, 1981 (reprinting of 1958 edition, New York: Praeger).
  • Hilton, Ordway Scientific Examination of Questioned Documents, New York: CRCPress, 1993 (reprinting of 1982 revised edition, New York: Elsevier).*Kecskeméti, Istvan, and Mika Seppälä, “False-colour Infrared (FCIR) Imaging: An Inexpensive Method for Identifying Iron-gall Ink by Standard Digital Camera,” Papier Restaurierung,Vol. 7, no. 1, 2006, pp 18 - 23.
  • Mitchell, C. Ainsworth, Inks: Their Composition and Manufacture; Including Methods of Examination and a Full List of British Patents, London: Charles Griffin,1937.

UV/Visible Fluorescence

Additional Resources