Conservation Portfolio Home
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Silent No More:
The Material Analysis of an American Dummy BoardThese life-size painted wooden cut-outs, known as dummy boards, are fun and engaging objects. I was shocked to find that so little research has been done on them since the late 1970s.
I chose to perform an in-depth technical study of the materials used on this dummy board of a man in Turkish costume from the Germantown Historical Society so that there will be a basis for comparison in future research and investigation of other collections.
One of the questions surrounding this particular dummy board is its early provenance and date of manufacture. It was my goal to establish greater evidence for the date of manufacture through examination of the material composition.
I also believe that the materials and methods of paint application can contribute to a better understanding of the social significance and meaning of these objects. Some microscopic investigation of the paint stratigraphy was performed as part of the initial conservation examination.
The following images summarize the project and significant findings. This project was presented at the 2015 Association of North American Graduate Programs in Conservation (ANAGPIC) conference. Click here to read the technical report or the complete conference paper.
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Key findings of this study were presented at the 2015 Association of North American Graduate Programs in Conservation (ANAGPIC) Student Conference. Read the full paper here.
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Performing X-Ray Fluorescence Spectroscopy on the dummy board.
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A handheld Bruker Tracer II-SD XRF with a rhodium x-ray tube was used because of the size of this object. All spectra were obtained at 40 kV and 9.6uAmps for a collection time of 60 seconds.
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The XRF data mostly confirmed the potential pigments that had been previously identified with Polarizing Light Microscopy.
These pigments fit with an 18th-century American palette. The XRF analysis did not clearly resolve the original color of the pants or belt. They could have been simply an off-white or a yellow color, produced by an organic dye. The latter is likely given the muted appearance of the background of the pants compared to the bright red decorative pattern on top, likely painted with vermillion due to presence of mercury.
Observations using polarized light microscopy (PLM) suggested the use of Prussian blue for the Turkish dress. The lack of major iron (Fe) peaks in the XRF data and Scanning Electron Microscopy maps corresponding to the blue paint layer do not negate the presence of Prussian blue. This pigment has a very high tinting strength so little is typically added as a mixture with white. Also, no cobalt or sodium were detected that could suggest the use of smalt or ultramarine. Further analysis is planned with Raman spectroscopy and Fourier Transform Infrared Spectroscopy to confirm the use of Prussian blue.
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Photomicrograph of dispersed pigment sample from red decoration.
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Dispersed red pigment sample in crossed polars, characteristic of vermillion and lead white mixture.
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Documentation of sampling area for cross section X.8
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Cross section sample from the top of the blue turban. This sample was prepared for Scanning Electron Microscopy--Energy Dispersive X-Ray Spectroscopy by trimming the resin cube and coating the perimeter of the sample with carbon powder paint (colloidal graphite in isopropanol). An EVO MA15 Zeiss SEM operated by Dr. Jennifer Mass, with Bruker XFlash 6130 detector was used to collect data from the sample at 20kV and 1.804 Amps across a lathanum hexaboride filament for about 10min for each collection area. The instrument was run in variable pressure mode around 152 Pascals. Images were generated with the accompanying Esprit 1.9 software package.
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Back scattered electron image of same cross section sample. False color is used to map elemental composition throughout the imaged area. Lead (Pb) is strongly present throughout the entire sample corresponding to lead white, used in the preparatory layers and also for tinting the blue layer. The dark black chunky pigments are likely carbon particles. The large calcium particle is likely a chalk filler used in the preparatory layers. The iron (Fe) is concentrated in the preparatory layers and is likely associated with earth pigments. Aluminum (Al) and silicon are often also associated with earth pigments. However, the Al here appears in the wooden substrate and near the finish coatings. The Al could be acting as an oil drier.
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The abundance of Pb in the painted surface of this object has contributed to lead-soap formations. The photomicrograph above (250X) of a cross section from the blue Turkish dress clearly highlights the lead soap circular agglomerates. The red particles of minium or red lead forming within one of the aggregates are extremely visible under UV light.
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Paint stratigraphy of another cross section sample taken from the blue robe. Two of the coating layers are very thin and would not be able to be isolated for identification within a cross section using Attenuated Total Reflectance Spectroscopy without synchrotron radiation.
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In order to try to resolve the individual components of each of the varnish layers I tried an alternative approach. There is an area on the chest of the figure that was previously covered by a paper label. Examination under UV light suggests that this area was covered during the final coating application. I took scrapings of the surface coating under magnification from the area covered by the paper label to represent the thick "natural resin" coating and the area next to it to represent the thin "oil coating."
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The samples were prepared with MethPrepII reagent for Gas Chromatography-Mass Spectroscopy analysis with a Hewlett-Packard 7820A gas chromatograph equipped with 5975 mass selective detector and G4513A automatic liquid injector. The above spectrum is from the area covered by the paper label.
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Spectrum for coating sample in the area covered by the paper label. There is a noticeable difference between these two spectra. Mainly, the first spectrum containing the final thin coating has a greater wax component and less pine resin. The second "natural resin" coating is likely mostly made of pine resin with some drying oil.
