RTI of Etruscan Bucchero Fragments at Poggio Colla
Heather White, Conservation Intern
As a 2014 Etruscan Foundation Conservation Fellow, I was afforded the opportunity to join the Mugello Valley Archaeological Project (MVAP) at Poggio Colla this season and it has been an incredible experience! As part of my fellowship, I teamed up with head conservator, Allison Lewis, to investigate the applications of Reflectance Transformation Imaging (RTI) on bucchero vessel fragments and other Poggio Colla artifacts. RTI essentially blends a series of photographs of an object under different angles of light to create a file (a polynomial texture map) that can be interactively explored by the viewer using an adjustable light source, or a “virtual torch”. This imaging technique highlights the subtle features of an object’s surface in high detail, and we found it an especially useful field tool for the documentation and study of worn stamped bucchero decoration, fabrication related marks on bucchero surfaces, and incised characters on ceramic and stone surfaces. Check out my blog about the project at Heather White's RTI Project Blog, and enjoy the images below!
Fig.1. The birthing stamp (inv. PC 11-003), found on a bucchero fragment,
measures just around
a centimeter in height and is worn, requiring magnification and
raking light to
imagery. [Photos courtesy of Dr. Phil Perkins, The Open University].
Fig. 2. We were able to disassemble a standard desk lamp to become our movable light source,
much to our excitement! This imaging technique was affectionately called “A Thousand
Points of Light” amongst the staff, and it was pointed out that it’s quite a ritualistic
(appropriate for the sanctuary site) as we huddle on the floor around an ancient artifact
with a single torch lighting us.
Fig. 3. Items inserted in frame for image processing or posterity (such as the black spheres,
grey scales, or labels) can be cropped out in the final stage of processing in RTIBuilder
so that your final product is simply your subject, to be navigated and explored in RTIViewer.
Fig. 4. When you open RTIViewer, you have several options at your disposal: you can control
your light source; you can zoom in and out on your subject and move around over its surface;
you can take a snapshot of your field of view (which saves as a jpeg and XMP file); and you
can play with a diverse range of rendering modes available in the dropdown menu.
Fig. 5. The different rendering modes can emphasize or deemphasize particular surface
characteristics, and some modes allow you to study the surface without the distraction
of surface pigment/colors.
Fig. 6. An incised and stamped bucchero sherd (inv. PC 13-075).
Fig. 7. A bucchero sherd (inv. PC 14-038) with reticulate burnishing, nearly invisible under even
light (note the ‘Default’ image). Modes like ‘Normal Unsharp Masking’ can reveal the very
subtly recessed burnishing marks, and others like “Diffuse Gain’ can contrast them.