PARTICLE CHARACTERISTICS OF PRUSSIAN BLUE IN AN HISTORICAL OIL PAINT
Frank S. Welsh
THE ANALYSIS OF HISTORIC ARCHITECTURAL PAINTS involves not only the identification of layers and colors of paint, but also it requires the accurate analysis and identification of the component pigments in the paint films. This is either out of historical, empirical interest or else out of an interest to more accurately understand a paint film's original color. Most often, though, the identification of pigments is undertaken to help prove the age of the paint film, since many pigments are commercially prepared and were not, therefore, necessarily available before a certain time.
Thirty years ago, an attempt was made to identify an original paint's component pigments at Independence Hall; however, the findings from the analyses were inconclusive. The equipment and information available for the analysis at that time was not much different than that used for this recent study, which was undertaken in an attempt to answer the lingering questions. What has changed in the intervening years is our increased knowledge of the materials to make architectural paints 200 years ago and, consequently, what we might expect to find in them. With our enhanced knowledge and expectations, the full capabilities of the variety of scientific instruments available to us can be best put to use.