Wax

Michele Cammarosano

Waxes are lipid materials characterised by esters of long-chain carboxylic acids, solidifying at room temperature and exhibiting high hydrophobicity. Natural waxes stem from animal (beeswax, Chinese wax, lanolin, spermaceti wax), vegetable (carnauba, candelilla, esparto wax, Japan wax), and fossil (paraffin wax, montan wax, ceresin) origins (Colombini and Modugno 2009, 10–12). Throughout history, waxes have served various purposes, including sealants, coatings, polishes, ‘lost wax’ technique, balms, cosmetics, candle production, encaustic painting, ceroplastic art, and writing tablets (Büll 1977). Beeswax (Hepburn et al. 2014, 16; Fröhlich 2000), exploited since the early Neolithic, stands out as the principal wax type documented as a writing support, namely as the fundamental component of the wax paste in wax figurines (first attested in 21st c. BCE Egypt; see Raven 1983), wax sealings (first attested in 15/14th c. BCE Egypt, Carnauba wax was occasionally used for producing sealings in the Modern period), and wax tablets. The latter, consisting of a single board or comprising multiple ‘leaves’ bound together, feature a framed recess holding a beeswax-based surface for scratching or impressing with a stylus. Erasing marks is easily done with a spatula or globular tip, enabling immediate or delayed re-inscription. Originating in Southern Iraq around the late third millennium BCE, wax tablets gained popularity across the entire ancient Near East (Cammarosano et al. 2019), and subsequently spread via the Levant to the Mediterranean basin. Prominent rewritable media in the Classical world, the Middle Ages and Early Modern Europe (Lalou 1992; Chartier 2005), wax tablets represent the earliest precursor to the modern book in codex form (Boudalis 2018), and stand as one of the longest-lasting manuscript forms in history.

A wax paste suitable for writing needs to strike a delicate balance between softness (for enabling inscription and erasure) and hardness (for text stability). This optimal equilibrium is not fixed but hinges on script nature, specific text requirements, and environmental constraints. Mechanical properties rely on environmental temperature, beeswax quality, and added substances. Pure beeswax's stickiness and translucent colour deem it unfit as a writing surface, prompting the addition of other substances with a triple purpose: adjusting consistency and plasticity, influencing colour, and cost-effective blending with more common materials. Philological sources and scientific analyses provide insights into the diverse substances incorporated into beeswax for inscribed figurines, writing tablets, and sealings throughout history. Evidence for ancient Egypt witnesses the addition of resins, oils, and pigments (Büll 1977; Serpico and White 2000). Ancient Near Eastern evidence is restricted to yellow ochre, arsenic sulphide (orpiment), and potentially (sesame) oil (Cammarosano et al. 2019). In contrast, evidence from the Classical period and the Middle and Early Modern Ages reveals a more extensive list of additives in various proportions and combinations, including oils, resins, turpentine, dairy products, honey, ochre, charcoal, soot, copper acetates (verdigris), cinnabar, red lead (minium), azurite, and basic lead carbonate (white lead) (Büll 1977; Oltrogge 2005; Weirauch and Cammarosano 2021). The colour of the resulting paste depends on the added ingredients, ranging from ochre and golden to black, red, green, and even blue. The plasticity criteria for sealings differ from those for wax tablets, as the former are intended to remain stable over time once impressed, while the latter as a rule aim to be easily erasable. Therefore, individual examples of inscribed wax mixtures are unique, and should be treated accordingly.

History of the material as Written Artefact

The use of wax (mixtures) as a writing surface is first attested in the 21th c. BCE in Middle Kingdom Egypt (11th dynasty) and in Southern Mesopotamia (Ur III period). In Egypt, wax figurines were sometimes provided with inscriptions, either inked directly on the wax surface, or on plaques that were subsequently applied onto the object (Raven 1983). Inscribed wax objects are attested in several other periods and cultures. In Mesopotamia, the context is the momentous invention of wax tablets (at times bound together as concertinas or books), a groundbreaking writing technology that enjoyed widespread and uninterrupted use in the Ancient Near East, the Classical world, and Medieval and Early Modern Europe until the 19th c. CE. The third major context for the use of wax as a writing surface is sealing practices. The earliest attestations of wax mixtures used as sealings, i.e. as a recipient of seal impressions, date from ancient Egypt (18th dynasty; Hayes 1990), but became widespread only in Late Antiquity and the Middle Ages. 

Types of analysis that can be carried out

Several methods, both destructive and non-destructive, can be applied in studying wax mixtures in written artefacts:

• Optical microscopy and RTI help observing texture and details of the artefact, and can be employed for enhancing legibility in the process of text edition.
• 3D laser scanning microscopy can be used for precise measurement of relevant features, such as shape and dimensions of written traces; optical and electronic scanning can be used for analysis of specific elements embedded in the wax mixture, such as hairs (Charlier et al. 2016).
• X-ray micro-radiography and micro-tomography can be used for inspecting volumetry and morphological structures within the wax mixture (Karch et al. 2016), thus for accessing marks that may be present beneath the wax layer in wax tablets.
• A multianalytical approach can be used for the characterisation of beeswax and added components, such as pigments, resins, and fats. This includes μ-FTIR, μ-Raman and SEM-EDX (see Scanning Electron Microscopy and Electron Microprobe Analysis) spectroscopy as well as mass spectrometry techniques, ideally used in combination (DEP-MS, Py-GC/MS, THM-Py-GC/MS; see Hahn 1995, Regert 2005; Regert 2009, Serpico and White 2002; van den Berg et al. 2000; Ferreira et al. 2016).
• Ideally, the analysis should be able to distinguish the components originally present in the mixture from those that may have been added as a result of restoration and conservation processes (including resins and waxes, both natural and synthetic). In addition to the analytical methods listed above, Compound Specific Radiocarbon Dating (CSRA) (see How to Date My WA?) can be used for this purpose.
• Palynological analysis can be used for revealing traces of pollen and microorganisms nestled within wax blends. While the concept of genomic analysis holds promise for sequencing the DNA of honeybees and other organisms (see DNA Analysis and Bioinformatics and Proteome Analyses), the conventional techniques applied in extracting and processing beeswax normally result in a scarcity of genomic material of adequate quality (Kasso et al. 2023). Illumina high-throughput sequencing has proved useful for investigating microorganism and metabolite diversity in wax seals, thus for better assessing biodeterioration processes (Szulc et al. 2020).