XRF analysis of Ukiyo-e prints

Overview

Elements detectable by XRF can be associated with reasonable confidence to specific inorganic materials in the prints, given the relatively narrow range of inorganic materials thought have been used in Edo period prints. For example:

Detection of iron in a red or red-brown area likely indicates the presence of red earth or ocher.
Detection of copper and zinc in a metallic-looking area likely indicates the use of ground brass metal.
Detection of lead in an orange-red area probably indicates red lead, while detection of lead in a white area probably indicates lead white.
Detection of mercury in a red area likely indicates vermilion (or its natural equivalent cinnabar).

Detection of some elements can narrow down possibilities. For example, arsenic in a yellow area (or a green made from a mixture of yellow and blue colorants), could indicate one of three specific colorants, all of which are arsenic sulfides. The most likely is orpiment, a natural mineral. In the later part of the Edo Period, a synthetic pigment of the same chemical composition as orpiment was manufactured, and this artificial pigment cannot be distinguished from the natural mineral by XRF alone. There is also another yellow-colored arsenic sulfide, pararealgar, but to date this compound has not been specifically identified in Japanese prints.

XRF Reference Spectra

Below are XRF spectra from samples of most of the inorganic colorants that have been historically mentioned as having been used in Ukiyo-e printing along with a few other colorants that are known to have been used in paintings at that time period (figs. 1-9).

Figure 1. XRF spectrum of orpiment (As peaks, small S peak)
Figure 2. XRF spectrum of iron oxide yellow (Fe peaks, some small peaks for other elements like K, Ca)
Figure 3. XRF spectrum of iron oxide red (Fe peaks, some small peaks for other elements like K, Ca)
Figure 4. XRF spectrum of brass (Cu and Zn peaks)
Figure 5. XRF spectrum of calcite (Ca peaks)