The volume Archeologia e archeometria delle miscele leganti di Aquileia romana e tardoantica (II sec. a.C.–VI sec. d.C.), published by Simone Dilaria (D.) in 2024 for the series Costruire nel mondo antico by Edizioni Quasar, proposes a methodologically innovative approach to the analysis of binding mixtures (i.e., mortars, concretes, cocciopesto, and plasters), restoring their interpretative centrality in understanding the building, economic, and social processes of the city of Aquileia, one of the main urban centers of northern Italy in Roman times.

The result of a decade of field research in Aquileia, synthesizing years of studies conducted by the author at the University of Padua, the book provides a diachronic analysis of the most ubiquitous and, at the same time, most neglected building material in the history of ancient architecture: mortar. The research is distinguished by the large breadth of the sample analyzed: over 370 samples (or 430, if individual layers are counted) – distributed among masonry structures, floors, and plaster – covering a period of over eight centuries, from the 2nd c. BCE to the 6th c. CE, taken from contexts relating to a wide range of structures (public, private, monumental, and functional). The entire methodological approach is based on a multitechnique petrographic, mineralogical, and microchemical analysis, which guarantees a very high level of detail and reliability of data. This impressive amount of data has resulted in a book that stands out for its breadth, methodological depth, and interpretative ambition. The systematic study of binding mixtures, especially when supported by archaeometric analysis, makes it possible to move beyond artificial disciplinary boundaries and to reconstruct the building process as a coherent whole, in which materials, techniques, and labor are deeply interconnected. By focusing on these materials – produced on site, frequently from local resources – one gains access not only to construction techniques and material supply, but also to the organization of work, the distribution of skills, and the transmission of knowledge within and across building sites. In this perspective, binding mixtures offer a privileged lens through which to investigate the dynamics of ancient construction, bridging the gap between architecture, decoration, and craft practice, and revealing the underlying unity of what has too often been studied in isolation.

The originality of this research is evident on several closely interrelated levels. Its real strength certainly lies in considering binding mixtures as the common denominator of all building, construction, decorative, and architectural activities. Mortars, concretes, cocciopesto, floors, and plasters, produced directly on site often with local materials, are perhaps the most “in situ” materials in Roman construction, to use the author’s expression, and considering them together allows us to identify, through variations in the mixtures, the phases of construction activity, the distribution of skills among the work teams, and the evolution of craft practices over time, overcoming disciplinary barriers that have no reason to exist, as walls, floors, and plaster share not only the time and place of execution, the construction site, but also materials and techniques and, therefore, knowledge, and – possibly – skilled workers.

The second merit of the volume is its ability to translate the “raw” archaeometric data into a means of telling a human, social, and technological story with the ambition of offering a synthetic view of the transformations in construction techniques in Aquileia from a diachronic perspective. The entire work is characterized by a strongly interdisciplinary approach and stands out for its adoption of an interpretative paradigm that places the “recipes” for building materials at the center of historical investigation. The archaeometric approach is not an end in itself, but it allows access to a wealth of data that would otherwise be inaccessible: from the origin of raw materials to supply chains, from the structure of construction sites to the hierarchy of workers, from construction choices to the economic logic underlying building investments. What emerges is a new image of the ancient city, understood as a complex organism in which material culture and technical-productive culture interact deeply with historical and territorial dynamics.

The volume, almost 600 pages long, is richly illustrated, with excellent print quality that makes it a beautiful book in every sense. The text is divided into three main sections, followed by a third conclusive part with the synthetic results. In the first part, the author outlines a historical profile and defines the binding mixtures, tracing a broad chronological overview from prehistoric times to Late Antiquity (29–72). It systematically addresses technical terminology, the analysis of components (binders, aggregates, additives, water), the main reactive phenomena (such as pozzolanic reaction), and the literary sources that document the use of these materials. This section provides the necessary theoretical and lexical framework for interpreting the subsequent analytical data.

The second part, the heart of the volume, presents the results of an impressive sampling and archaeometric analysis campaign on over 370 samples from numerous architectural contexts in ancient Aquileia, including the city walls, the theater, the amphitheater, the Grandi Terme, the river port, the Theodoric complex, the Insula delle Bestie Ferite, and the Domus di Titus Macro (75–419). After illustrating the geographical, geomorphological, and topographical characteristics of the site, the author describes the methodology adopted, based on the integrated use of petrographic analysis using optical microscopy on thin-sections and mineralogical analysis, combining electron microscopy, spectroscopy, and X-ray diffraction. Chemical analyses such as Raman spectroscopy and X-ray fluorescence are also used, particularly for certain pigments. This is followed by a long section presenting the results in relation to the different contexts. The analysis is not limited to the technical-scientific description of the materials but pursues three main objectives: to define the physical-mechanical properties of the binding mixtures, to reconstruct the production technology used, and to trace the origin of the raw materials. This opens the way to other questions, such as the architectural function, the possible recycling of raw materials, the underlying economic choices, and the chronological and social implications, always in relation to the archaeological context, which in Aquileia can be defined as privileged, thanks to the numerous, important, and recent research conducted in the area by the universities of Padua, Venice, Verona, and Udine for many years now.Footnote ¹ The possibility of analyzing different contexts simultaneously allows for a multilevel reading – micro, meso, and macro – ranging from the analysis of the individual material components of a structure or cladding to the overall practices of specific construction sites, to the organization of supplies and labor on an urban scale.

The latter is the subject of the third and final part, which offers a cross-sectional summary of the analytical evidence, reclassifying the types of binding mixtures identified (aerial and hydraulic mortars, stuccoes, cocciopesto, concrete, earth mortars, etc.) in relation to their composition, functional purpose, and context of use (423–550). The building history of the city is also reconstructed through the lens of changes in materials, from the Republican works, which show a strong technological consistency, to the Late Antique and Byzantine phases, marked by more heterogeneous solutions and sometimes by practices of saving or reuse.

This tripartite structure of the volume reflects its hybrid nature, as the book is halfway between a technical-educational manual, a scientific treatise, and a long-term archaeological synthesis. This nature is also clearly perceived in the linguistic register of the book, which alternates between dense and extremely technical passages, necessary and intended for experts as a presentation of pure archaeometric data, in its completeness and complexity, and discursive interpretative passages, which retrace the history and vicissitudes of one of the most important Roman colonies in northern Italy. At the same time, the result is a work of synthesis, which aims to serve as an exemplary methodological model to be replicated and applied in other contexts. This choice of variable language (sometimes technical, sometimes informative) makes it a book that appeals to archaeologists as well as specialists in heritage science.

The volume stands out precisely for this epistemological synthesis between disciplines, not only in form but also in substance, showing how true archaeometry does not lie in the accumulation of graphs and numerical values, but in the ability to transform technical data into narrative, keeping the balance between analytical rigor, theoretical awareness, and narrative skill. In this case, D. embodies the ideal figure of the archaeometrist, as a single person capable of mastering the entire cognitive process: from defining archaeological questions to collecting data, analyzing them, and interpreting them. In most cases, this figure is not represented by a single person but by a team of different skills, united by a common goal in a transdisciplinary approach. On the one hand, we have the archaeologist, who formulates the questions, selects the contexts, and provides the historical-topographical framework for interpretation; on the other, we have the specialist in applied heritage sciences, often a chemist or geologist, who performs the analyses and produces the physical-chemical data. However, these two components do not always communicate effectively, although much has been done in recent years: their respective terminologies, priorities, and operating methods are not always compatible, and this hinders the crucial process of transposing technical data into archaeological discourse. D.’s merit lies in having embodied a rare and valuable third figure: one who, without negating the technical, methodological, and scientific specificities of each discipline, is able to mediate, translate, and synthesize languages and methods, exploiting the historical context to extrapolate useful data and transforming analytical results into a coherent historical narrative.

What lessons can we learn from this approach? It is not a question of expecting every archaeologist to further specialize in chemistry or vice versa, but of building a common language, a shared epistemological basis that allows each expert to contribute according to their own skills, within an integrated collaborative framework. It is precisely from this dialogue – aware of the specificities of each field – that this “third voice” can emerge, that of interpretative synthesis, which is the true ultimate goal of any archaeometric study. And it is only by multiplying opportunities for discussion, dialogue, and cooperation that this voice can be consolidated. To achieve this, a crucial first step is to speak the same language. However, even in a field as narrow as the study of decorative elements, we have not yet managed to agree on the terms to be used, for example in the naming of the preparatory layers of the tectorium.Footnote ² In the Italian archaeological community, represented by the recently founded Associazione Italiana Ricerche Pittura Antica (AIRPA), the distinction between intonachino, intonaco, and arriccio has become widespread;Footnote ³ in the field more strictly related to the study of mortars, the same layers are named respectively intonachino, arriccio, and rinzaffo;Footnote ⁴ conservators and modern-day fresco painters often refer to the terms intonaco and arriccio;Footnote ⁵ if we then consider other languages or other disciplines, the differences multiply – for example, in the French-speaking community represented by the Association Française pour la Peinture Murale Antique (AFPMA) it has been decided to abandon the traditional definitions and refer only to “couche de finition” and “couche de préparation,” or simply to number the layers, starting from the painted surface.Footnote ⁶ This terminological heterogeneity, which is not isolated, highlights the need to redouble efforts to achieve greater standardization. To this end, an active role for the federation could be desired by international scientific bodies such as the Association Internationale pour la Peinture Murale Antique (AIPMA), or by working groups set up between the various research teams active in the field. D. offers to clarify this lexical difficulty by offering clear terminology and definitions, using a nomenclature based on granulometric, compositional, and functional criteria (378–408 and 522–27). The distinction between intonachino, arriccio, and rinzaffo is primarily based on their stratigraphic position and technical function within the tectorium, and secondarily on differences in granulometry and texture. The intonachino constitutes the outer finishing layer supporting the pictorial film and is characterized by a very fine and homogeneous aggregate (generally < 0.5–1 mm); the arriccio, directly underlying it, presents a finer and more regular texture than the deeper preparation layers, with a medium granulometry (ca. 1–3 mm); the rinzaffo, forming the innermost layer in contact with the wall, is instead defined by a coarse and heterogeneous aggregate (often > 3–5 mm), reflecting its function of levelling and filling irregularities of the support. However, while the intonachino can be clearly distinguished from the preparatory layers, the differentiation between arriccio and rinzaffo often remains ambiguous in practice, especially when you have lost the connection of the plaster to its original wall, so that they can be grouped together as a single category (arriccio/rinzaffo). The same strict criteria allow D. to make the distinction between mortars (malte) and concrete (calcestruzzo), according to the size of the aggregate granulometry: aggregate under 5–8 mm for mortars, over 5–8 mm for concrete (37–57). The position of the mortar/concrete needs also to be taken into consideration: D. distinguishes structural mixes from coating mixes.

A second point that emerges clearly from reading D.’s book is the absolute necessity, already advocated on many occasions, to establish common protocols and build shared databases. Large-scale projects, such as the one conducted in Aquileia, demonstrate the importance and usefulness of quantitative and statistical data, which enrich the archaeometric results by taking a broader view than the individual material analysis of a single context. The only condition for obtaining these results is to ensure the interoperability of the data in order to extrapolate usable quantitative data. The Aquileian dataset highlights both the potential and the current limits of archaeometric research. The increasing availability of analytical data, generated by the progressive development and wider accessibility of laboratory techniques, calls for more synthetic and integrative studies capable of moving beyond site-specific analyses. In this respect, urban contexts such as Aquileia offer particularly favorable conditions, as they concentrate a large number of samples within a relatively limited topographical area. This density of data allows for multiscalar interpretations, ranging from the micro-level of individual construction sites – including technical choices, recipes, and building practices – to the meso-level of workshops, labor organization, and shared technical traditions operating within the same urban fabric.

At the same time, the construction of broader interpretative frameworks at the regional and provincial scale remains more challenging and requires a larger accumulation of comparable datasets. Only through the progressive integration of multiple case studies will it be possible to define wider patterns in the production, circulation, and use of mortar-based materials across the Roman world.

The systematic integration of the archaeometric data in the archaeological interpretation of buildings and decorations allows us to deepen our knowledge on a large variety of important questions. For instance, the author touches on a methodologically and epistemologically crucial issue: that of the organization of the construction site and the relationship between workers and different trades (482, 495–527). Archaeometric studies conducted on Aquileian mortars highlight the clear distinction between the mortars used for masonry, flooring, and plastering: not only do they meet different functional requirements, they also testify to the use of specialized teams, active in different phases and with different skills within the construction site. Plaster mortars, in particular, have more refined formulations than masonry and flooring mortars. However, there are many elements common to the production of the various types of binding mixtures.

Structural mortars display a high degree of compositional standardization, with lime-based mixtures consistently associated with particular building techniques and used with only minor variations, sometimes sufficient to distinguish construction phases but overall indicative of a codified and shared technological repertoire. This regularity, together with the controlled selection of raw materials and preparation methods, points to a well-organized construction process governed by consistent technical criteria.

A comparable tendency is observed in floor systems, where recurring preparatory solutions suggest the existence of a standardized modus operandi, albeit with greater compositional flexibility and frequent inclusion of coarse or recycled materials adapted to functional requirements. Plasters, by contrast, exhibit a higher degree of variability in aggregate selection and additives, even though their stratigraphic organization and certain technical solutions remain broadly shared, indicating a common technical background applied with greater adaptability.

At the same time, the recurrence of similar materials across different construction domains – for instance, the secondary presence of aggregates initially introduced for structural purposes within preparatory layers of floors and plasters – suggests a circulation of materials within the same building site and the existence of interconnected supply practices. A matter of great interest, discussed several times by the author (esp. 435–57), is the phenomenon of recycling in the mixing of mortars, present at all levels, in all types of construction, and in every period. Shells, crushed plaster, tile processing waste, and fill sand (possibly linked to the reuse of the ballast of ships in the port area) appear in the mortars. These details provide a glimpse into economic practices, reuse logic, and forms of production rationalization that are often elusive, but which microscopic observation of the mortars allows us to highlight clearly.

Another issue addressed concerns construction site logistics and, in particular, the supply of raw materials. Particularly interesting is the reflection on the most important ingredient in the preparation of mortars, but also the most invisible of all: water, which was needed in very large quantities at all stages of construction (432–35). D. hypothesizes that in some peripheral construction sites in Aquileia, far from water supply networks, brackish water from the canals was used. The hypothesis is based on the presence of saline components (M-S-H [magnesium silicate hydrate] phase) in the binder of the building elements. These elements are completely absent in the painting mortars, a sign that even in more difficult contexts, water quality was an important factor in the preparation of plaster. In this case too, the combination of analytical data and archaeological context provides a concrete picture of the operating conditions on the construction sites.

I would like to conclude this brief review by highlighting what D.’s book reveals about the role of mortar analysis in the study of ancient wall painting, particularly in the identification of painters’ workshops. In the corpus analyzed by D., mortars linked to painted plasters represent a small part, with 63 plaster samples out of 378 samples (363–419). Of these, only seven relate to in situ paintings, the rest coming from fragmentary contexts in secondary deposits. Despite lacking their original context, these fragments are of extraordinary importance for our understanding of ancient painting, as they often constitute the only material evidence of lost or unexcavated buildings, whose plastered decorations were frequently reused in fill layers for their hydrophobic properties.Footnote ⁷ In the volume, the author devotes a significant part to the preparatory mortars for wall plaster, offering a technical and chronological interpretation that opens up new perspectives on the work of the craftsmen and the organization of ancient building sites. The observation of similar characteristics between the preparatory layers of plaster from different environments raises crucial questions about the identification of possible workshops through the technique: such similarities may be indicative of shared practices, widely used technical standards, or markers identifying specific practices linked to individual craftsmen working in different areas, in this case a city.

However, the picture that emerges from Aquileia suggests a more complex interpretation: the main differences in the preparation of the plaster do not seem to depend on the functional nature of the context (public or private) or the economic level of the patron, but rather on chronology. In the volume, D. proposes a historically informed interpretation of the technical transformations observed in the mortars of Aquileia, relating them to the main evolutionary phases of the colony and the sociopolitical changes that marked its life (529–50). In the Late Republican period, the material evidence suggests strict adherence to the technical and construction models of central Italy, perhaps linked to the arrival of painters from the central power, as demonstrated by the composition of the mortars and the adoption of procedures codified in treatises such as that by Vitruvius. With the beginning of the Imperial period, however, there was a gradual rise in local craftsmen, who came to fully master building and decorative techniques, developing recurring working methods and increasing standardization in the preparation of mortars. This phase was associated with the emergence of figurative languages and technical solutions recognizable as regional, though still inspired by urban models. From the 3rd c. CE onwards, and even more significantly in Late Antiquity, there was a gradual dissociation from traditional prescriptions. Techniques became more heterogeneous and less codified, with a tendency toward thinner and fewer preparatory layers – both in mosaics and wall paintings – and the adoption of “malte grasse,” characterized by a greater quantity of binder than aggregate.

These changes should not be interpreted as an indication of a decline in quality: the raw materials remained of good quality, but the functional requirements, the skills of the workers, and the cultural contexts of reference changed. The workshops active in the Late Antique period seem to have operated without a shared theoretical background and without systematic recourse to the rules inherited from the Vitruvian tradition, preferring practical and flexible solutions that reflect a different balance between technical standards and freedom of execution. This evolution, in practice, can be perceived indirectly in ancient treatises: by comparing Vitruvius and Pliny with later texts, such as Marcus Cetius Faventinus and Rutilius Taurus Aemilianus Palladius, D. identifies some differences that are reflected in the archaeological record. Contrary to popular belief, textual sources and material reality are not in contradiction, but rather reveal a transformation of technical practices over time. Emblematic in this sense is the fact that Palladius, unlike earlier authors, explicitly includes (recycled) marble among the materials suitable for lime production (Pall. Rust. 1.10.3).

D. proposes to extract from these summary observations on the diachrony of mortars some chronotypes of tectorium, intended as a tool for defining phases and periods. It is precisely the large number of samples analyzed that allows D. to identify macro-phases in the history of decorative techniques. Already in 1987 Alix Barbet had wondered whether the study of mortars could one day become a chronological marker.Footnote ⁸ Today, we can say that this is a realistic possibility, as the proliferation of studies on fragmentary painting and the attention paid to preparatory layers provide us with sufficiently large and representative corpora. Recent developments in absolute dating techniques for mortars using ¹⁴C are promising, as there are increasing attempts, to be handled with extreme caution, to analyze the carbon formed during the carbonation of the binder based on aerial lime, allowing us – at least in theory – to trace with some precision the moment when the mixture was applied and therefore the construction phase.Footnote ⁹

One element that is repeatedly highlighted, in Aquileia and elsewhere, is the fact that, over time, there has been a gradual simplification of the preparatory layers, both in terms of thickness and number, accompanied by an increasingly marked disproportion between binder and aggregate, which is generally evident in all types of mixtures. This slow deterioration in the quality of the tectorium is associated, by the author and others, with the gradual abandonment of wall painting as the preferred means of expression among elites in favor of marble coverings.Footnote ¹⁰ While it is certainly true that patrons’ interest in painting declined in favor of marble inlays from the 1st c. CE onwards, I do not think we can speak of a decline in or inferior quality of execution.Footnote ¹¹ The case of Aquileia confirms a picture that is also emerging at other sites, where the craftsmen always show a great knowledge of the properties of the materials and a high level of technical expertise. An important key to understanding this, in my opinion, lies in the increasingly widespread use of a secco painting, which also became the predominant technique in Aquileia, as evidenced at other sites, from the 2nd c. CE onwards.Footnote ¹² The execution of secco painting, which therefore requires the use of organic binders, is – unlike fresco painting – less dependent on the setting time of the mortar, which makes the technical quality of the preparatory layers secondary to decorative requirements. I believe that this interpretation deserves to be pursued in further studies, as the data at our disposal are beginning to provide a very consistent overall picture.

I will conclude by saying that this work goes far beyond the case study of Aquileia, which is already of great importance, given the exceptional nature of the site. D’s work proposes a replicable model for the study of construction technologies in the Roman world, based on the integration of earth sciences and archaeology. In this sense, the volume takes on a paradigmatic and methodological value, paving the way for new investigations into other ancient urban contexts. This book, therefore, lays the foundations for a new approach to the study of ancient building materials, proposing a methodological, terminological, and epistemological model that can guide future research not only on mortars, but on the entire building culture of the Roman world.