Thaw Conservation Center
From Drawing to Print: Abraham Bloemaert's Danaë Receiving the Golden Rain
About the imaging process
Conservators from the Thaw Conservation Center perform RTI image capture.
Documenting the elusive three-dimensional features of a print or drawing is difficult. This is because what can be detected on its surface at any given time is dependent upon how it is illuminated. Typically, raking light, emitted from a source held parallel to the work's surface, is used to exaggerate disruptions in the surface of a sheet of paper or in the media, making it easier to detect subtle disturbances such as flaking in paint layers or the incised lines of drawings that have been traced with a stylus for transfer. When documenting these nuances using normal photography, the raking light is constrained to a single fixed position, often arbitrary, when it is captured by the camera. While helpful, the visual information transmitted to our eyes is literally one-sided and, therefore, limited.
With the recent development of a specialized digital photographic technique known as Reflectance Transformation Imaging (RTI) by Cultural Heritage Imaging, the static nature of raking light photography is eliminated. Using RTI, a series of digital images is captured in which the artwork is illuminated from a number of different angles. These images are then synthesized into a single digital file to create a highly detailed virtual topographic map of the artwork's surface that can reveal impasto, brushstrokes, dents, tool marks, scratches and other traces of the artist's hand. Physical characteristic of paper, such as its surface texture and watermarks, are also recorded.
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The static raking light image of Bloemaert's Danaë Receiving the Golden Rain shows some indentations in the paper, but the RTI image is more revealing.
Using RTI, the conservators from the Thaw Conservation Center imaged Bloemaert's Danaë. When viewed in raking light the indentations are evident, but it is difficult to determine and accurately record the extent to which the drawing is inscribed. Imaging the drawing using RTI allowed closer examination. This technology revealed that the drawing was inscribed throughout the entire design, and not restricted to the principal figures as initially suggested. In this instance, RTI proved to be an indispensable tool in firmly linking this drawing with the engraving.