Beauty and chemistry: the independent origins of synthetic lead white in east and west Eurasia

The synthesis of pigments has played a crucial role in the development of art and cosmetics throughout history. While the corrosion method for synthesizing lead white emerged in Greece during the 4th century BCE, its origins in East Eurasia and its connection to beauty practices remained unclear. Lead white, a mixture of hydrocerussite and cerussite, is a significant pigment used extensively in painting and cosmetics. While its use in ancient Egypt and Europe is documented, its appearance in East Asia before the Common Era is less understood, with conflicting theories regarding its origin. This study aims to address this gap by analyzing white cosmetic residues from the Liangdaicun site in northern China, a significant archeological site dating back to the 8th century BCE, to determine the time and method of its synthesis and to establish the connection to cosmetic usage. The successful synthesis of lead white has been known to dramatically reduce the cost of production which in turn has allowed for its mass production and wide spread usage in both the East and West. This increased use of lead white across Eurasia has been observed to coincide with a rise in the popularity of makeup and has promoted the field of chemistry. Understanding the independent development of lead white synthesis provides crucial insights into the development of early chemistry and its relationship with societal practices.

Previous research highlights the early use of natural mineral pigments in prehistoric art and the subsequent development of synthetic pigment production. Examples include Egyptian Blue (ca. 3200 BCE), phosgenite (ca. 1400 BCE), China Purple (8th century BCE), and Maya Blue (8th century CE). The earliest known method for obtaining lead white involved mining natural cerussite, with evidence found in various regions including Southern Europe, Egypt, Mesopotamia, Iran, and the Indus Valley between the 5th and 2nd millennium BCE. The synthetic production of lead white, primarily through the corrosion method, began in ancient Greece during the 4th century BCE, as documented by Theophrastus, Vitruvius, Pliny the Elder, and Dioscorides. However, the origins of lead white synthesis in East Eurasia remained debated, with conflicting theories proposing either independent invention in China or introduction from Europe or ancient Egypt. The study sought to fill this knowledge gap by applying scientific methodologies to analyze archeological artifacts, something that has been lacking in the field. This approach allows for a more thorough understanding of lead white’s origins and use throughout time.

The research focused on white residue samples from miniature bronze cosmetic containers discovered at the Liangdaicun site in northern China, an aristocratic cemetery from the early Spring and Autumn Period (8th century BCE). The study employed a multi-faceted approach to analyze the residues. Microscopic observation using a Keyence VHX600 digital microscope and scanning electron microscopy (SEM) coupled with an energy dispersive X-ray spectrometer (EDS) examined the morphology and elemental composition of the residues. Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Powder Diffraction (XRD) were utilized to identify the mineral composition. Stable carbon isotope (δ¹³C) analysis and radioactive ¹⁴C dating further investigated the carbon source and age of the lead carbonate. The samples that were collected included LW-1 to LW-6 with detailed information included in Table 1. The acid hydrolysis method was used to generate CO2 for carbon and oxygen isotope analysis. Accelerator mass spectrometry (AMS) and isotope ratio mass spectrometry (IRMS) were employed at Beta Analytic Radiocarbon Dating Laboratory for analysis. Radiocarbon ages were calibrated against the IntCal20 atmospheric calibration curve. This multi-pronged methodology ensured a comprehensive characterization of the samples. A detailed examination of the tombs and their location are shown in Figures 2 and 3. Images of the bronze containers and residues are also included in Figure 4.

FTIR and XRD analyses identified the residues as primarily cerussite (PbCO₃), with phosgenite (Pb₂Cl₂CO₃) present in two samples. Microscopic analysis revealed elongated pseudo-hexagonal, acicular, and prismatic cerussite crystal morphologies, indicating formation through precipitation in solution, rather than the grainy crystals typical of the corrosion method. Stable carbon isotope analysis (δ¹³C values of −15.6‰ and −18.8‰) suggested a significant contribution from C₃ plants as the carbon source. Radiocarbon dating of samples LW-1a and LW-2a yielded calibrated dates slightly earlier than the tomb's burial date, but still within the range indicating a synthetic origin, as opposed to the significantly older dates (5000+ years offset) observed in natural cerussite. The presence of phosgenite further supports the synthetic origin, given its rare natural occurrence. The absence of pyromorphite and phosphorus, typically found in natural Chinese cerussite, provided additional evidence for a synthetic process. The study concludes that the lead white was synthesized through a precipitation method, involving the use of soluble lead salts, likely lead acetate produced by reacting PbO with acetic acid (vinegar), and a carbonate source, possibly from plant ash. The results establish the Liangdaicun lead white as the earliest known synthetic lead white, predating that of ancient Greece. Figures 5 and 6 depict the FTIR, XRD, and radiocarbon dating results, respectively.

The findings challenge the prevailing narrative regarding the origins of lead white synthesis. The independent development of the precipitation method in China contrasts with the corrosion method used in ancient Greece, implying separate technological innovations. The use of vinegar in the Chinese precipitation method points to an early application of wet chemistry, predating previously known examples by approximately 1000 years. The availability of vinegar in ancient China, facilitated by its widespread production during the Zhou Dynasty, played a pivotal role in the emergence of this synthetic process. The discovery sheds light on the interpretation of an ancient Chinese recipe, previously difficult to decipher, which now appears to describe the precipitation method. The study also highlights the significant cultural and social factors influencing lead white’s development, including the cultural preference for white complexion as a symbol of beauty and high social status, creating a strong demand for white cosmetics. This demand stimulated innovation in chemistry, with the discovery representing the earliest known case of inorganic reactions in aqueous solution, demonstrating the interplay of cultural preferences, economic resources, and technological advancements in shaping the development of chemical practices.

This study presents compelling evidence for the independent development of synthetic lead white production in East Eurasia, specifically highlighting the earliest known example found at the Liangdaicun site (8th century BCE), produced using a precipitation method. This discovery pushes back the timeline of wet chemistry practices in China by approximately 1000 years. The results underscore the independent development of lead white synthesis in East and West Eurasia and the significant role beauty played in driving these advancements. Further research should investigate the subsequent development of the precipitation method and compare the evolutionary trajectories of lead white production in both regions. Cross-disciplinary collaboration is essential for a more comprehensive understanding of ancient chemical practices and their societal impact.

While the study provides strong evidence for independent development, the precise carbon sources involved in the precipitation process remain uncertain. The slight offset in radiocarbon dates between the lead white samples and the tomb's burial date may be attributed to the incorporation of organic carbon from various sources, highlighting the complexities of radiocarbon dating of synthetic lead carbonates. Future work can explore the sources in more detail. Furthermore, the study's focus on a single archeological site limits the generalizability of the findings, although this is the first reported case of this kind.