A recent investigation into remnants of Roman wall paintings from northern Italy has uncovered a surprising application of Egyptian blue pigment. Unlike typical uses where pigment is merely applied to the surface, in this case, the pigment was integrated directly into the lime mortar beneath a vibrant marine scene.
Discovery of the Fragments at Torre di Pordenone
The fragments analyzed originated from the Roman villa at Torre di Pordenone, located in the region of Friuli-Venezia Giulia. Archaeologists located these pieces in secondary deposits within Sector 2 of the villa. The imagery depicted includes various marine species such as mullets, octopuses, and lobsters, all set against a striking blue backdrop. These fragmentary pieces are believed to represent portions of a painted fishpond, a decorative feature also found in other Roman sites like Pompeii and Brescia. By comparing these findings to similar marine-themed art, researchers have dated the fragments to the late first century or the early part of the second century CE.
Scientific Analysis of the Paint Technique
In this new study, a detailed examination of ten wall fragments was undertaken to understand the composition of the mortar layers and the blue pigment contained within them. Researchers employed various advanced techniques, including optical microscopy, scanning electron microscopy, and X-ray diffraction, to analyze the materials used in this work. The tests revealed cuprorivaite, the main crystalline component of Egyptian blue, present not only on the painted surface but significantly deeper within the mortar layer beneath it.
These analyses determined that some grains of Egyptian blue were found more than one millimeter below the surface. Raman spectroscopy confirmed their existence down to about two millimeters deep, with mappings indicating copper-rich clusters extending approximately three millimeters into the mortar. Such depths suggest an intentional mixing rather than mere pigment penetration, which is common in traditional fresco applications.
Implications of the Findings
The research indicates that Roman craftsmen might have mixed Egyptian blue with lime and aggregates to create a uniformly pigmented mortar. This method differs from the traditional fresco technique where pigments are generally applied over fresh plaster. The use of blue mortar likely served a practical purpose, providing a stable base for the intricate marine decor while also simplifying the workflow, reducing the need for coordination between plasterers and painters.
Interestingly, choosing Egyptian blue as a key pigment reflects both an aesthetic preference and economic decision-making. The study estimates that about five percent of the pigmented mortar consisted of Egyptian blue, suggesting a substantial investment in this expensive pigment. While red ochre was more commonly used for similar applications, the frequent incorporation of Egyptian blue throughout a mortar layer is rare.
Broader Context and Future Research
This study contributes to our understanding of the availability and usage of Egyptian blue in ancient Roman markets. The amounts detected in the Torre di Pordenone suggest a reliable supply for extensive decorative projects. The findings mark a rare instance of Egyptian blue being documented within Roman wall-painting mortars, potentially opening avenues for exploring other blue-themed wall decorations such as gardens and Nilotic scenes.
Future investigations aimed at this technique could reveal whether such methods were a common practice across various Roman sites or if they were unique to this particular villa. Such research might significantly enhance our understanding of Roman artistic techniques and material usage.