Chemical composition of architectural plaster at the Classic Maya kingdom of Piedras Negras, Guatemala
Highlights
► We study architectural plaster chemistry from Piedras Negras, Guatemala, a Maya center. ► Methods include X-ray fluorescence and complementary statistical analysis. ► Clusters of buildings differed from each other in plaster chemical composition. ► A rotational system of labor obligation is suggested.
Introduction
Plaster is a common building element that protected and adorned masonry architecture built by the Late Classic (A.D. 600–900) Maya Indians of modern-day southern Mexico and northern Central America. Plastered masonry architecture distinguished elite status from that of the commoners through the conspicuous scale of these buildings as well as the religious visual media provided by plastered architectural surfaces. In addition to serving engineering and symbolic roles, architectural plaster was perhaps the most technically sophisticated artifact produced by Maya artisans (Abrams, 1996), providing the basis for inferences concerning economic specialists (Abrams, 1994; Russell and Dahlin, 2007). Given the analytic potential of this artifact, architectural plaster from several Classic Maya sites has been chemically identified (e.g., Littmann, 1959, 1960, 1962; Hansen, 2000; Hansen et al., 1997; Hyman, 1970; Villaseñor and Graham, 2010).
The elite masonry structures at the Classic Maya kingdom of Piedras Negras, Guatemala, were all adorned with plaster (Fig. 1). Clustered within that site's Acropolis, these structures bore a 1–3 cm thick coating of hard, durable plaster. In 2000, Abrams visited the site and conducted an architectural energetic analysis – estimating labor costs – of some of this masonry architecture (Abrams, 2001). In the course of studying the building process, Abrams collected plaster samples specifically to test for the chemical distinctions of plaster on single buildings and among various buildings.
Here we present the results of X-ray fluorescence on 15 samples of plaster removed from six masonry structures from the elite center of Piedras Negras. This preliminary analysis indicates that the chemical composition of plaster was relatively uniform on individual structures, but that chemical composition varied among buildings. The labor organizational implications are then considered.
Piedras Negras was one of the largest Maya kingdoms along the Usumacinta River (Fig. 1). Between ca. A.D. 650 and 800, rulers built some of the highest quality masonry structures in the site's center known as the Acropolis. This portion of the site was established as the center of power by Yo'nal Ahk II at about A.D. 687 (Martin and Grube, 2000, p. 145). The plaster that adorned these structures (including those in our sample) was made throughout this Late Classic period (Escobedo, 1997, p. 67; Child and Child, 2001, p. 3).
All Maya plaster was a calcium-based cement derived from limestone. The cement that creates adherence in the plaster is the result of burning, or calcining, the limestone, a process well documented through observations of both indigenous and replicative behaviors (Morris et al., 1931; Hansen, 2000; Russell and Dahlin, 2007).
At Piedras Negras, it is likely that limestone was calcined on caleras, or wooden pyres, as described by Morris et al. (1931) and Erasmus (1965) rather than in semi-enclosed kilns (Abrams and Freter, 1996) or in deep pits (Abrams, 1996). Pits were more typical of Early Classic plaster processing and larger kilns have not been found at Piedras Negras. After the calera was carefully built, broken pieces of limestone were placed on top of the calera and burned in a controlled manner. After successful burning, the lime powder slakes, or hydrates, expanding in volume from 15% (Russell and Dahlin, 2007, p. 418) to as much as 32% (Abrams, 1996, p. 197).
After the lime powder has been slaked, an aggregate is added. At Piedras Negras, that aggregate was principally sascab, a naturally decomposed limestone abundant across the hilly dissected landscape along the Usumacinta River. It also has been suggested that plaster from earlier buildings could have been crushed and reused as an aggregate in newly-made plaster (Abrams, 1996, p. 198). Regardless, sascab as an aggregate can increase the volume of the finished plaster several-fold. Both Erasmus (1965) and Roys (1934) observed a 1:3 ratio of lime to aggregate in finished plaster, and Littmann (1960, p. 409) noted that “... only minor amounts of burned limestone were necessary...” to produce viable architectural plaster.
A traditional calera in northern Yucatan was observed to produce 11.33 m3 of “lime powder” (Morris et al., 1931, p. 225). With that volume expanded through slaking and the addition of an aggregate, each calera could typically yield between 20 m3 and 40 m3 of construction plaster.
In the present analysis, plaster was removed from six structures from the Acropolis (Fig. 2, Fig. 3, Fig. 4). The analyses described here involve fifteen samples (Table 1): Str. J-4 (n = 2); Str. J-6 (n = 3); Str. J-9 (n = 5); Str. J-7 (n = 1); Str. J-10 (n = 2), and Str. P-7 (n = 2). The samples from West Group Strs. J-6 and J-7 represent Court 1, whereas those from Strs. J-9 and 10 represent Court 2. Str. J-4 was considered an isolated and independent structure. Str. P-7 is a sweatbath north of the East Group. Multiple samples (n = 5) were selected from Str. J-9 to specifically test for variability on a single structure.
Section snippets
Methods
X-ray fluorescence was used to determine the elemental identities of the samples. X-ray fluorescence instruments can provide quantitative analysis that exceeds classical wet chemistry for substances like plaster (Skoog et al., 1998). The plaster analysis was completed with a JEOL JSM-5300 Scanning Microscope. The software was Series II Personal Computer Analyzer created by The Nucleus Inc.
All samples were ground by a mortar and pestle and adhered to graphite tape prior to analysis. Because the
Results
X-ray fluorescence revealed the chemistry of plaster from these samples. However, there exists no exact formula for calculating color or hardness from X-ray fluorescence data, and thus our current analysis does not address this question. Future studies may measure hardness per sample from physical rather than chemical studies.
Table 2 shows the average composition of the various samples per site area as well as the results of the comparative t-test analysis of plaster chemistry among areas at
Discussion
The results indicated that either the limestone that served as the base cement or the sascab that served as the major aggregate in the plaster (or both) varied in chemical composition (silica and magnesium content) on spatially and/or temporally discrete masonry structures at Piedras Negras. Our explanation for this pattern is that different quarries and outcrops for the limestone and sascab, respectively, were used as the source material for specific building programs. Although the sascab
Conclusions
This preliminary study analyzed plaster samples from the Classic Maya kingdom of Piedras Negras, Guatemala. The chemistry of these materials indicated local production with little variation within any single structure, but significant variation among structures. It is suggested that distinct limestone or sascab sources were exploited through time within the context of a rotational corvee obligation.
Acknowledgments
The authors thank the Instituto de Antropología e Historia de Guatemala (IDAEH) of the Ministry of Culture and Sports of Guatemala for permission to conduct this technical study, through a field and laboratory permit granted by then-Director, the late Dr. Juan Antonio Valdés, to Drs. Stephen Houston and Héctor Escobedo, Co-directors of the Piedras Negras Archaeological Project, 1997–2000, 2004. Funding for infrastructure and field support at Piedras Negras came from Dr. Kenneth Woolley and
References (22)
- et al.
The use of volcanic materials for the manufacture of pozzolanic plasters in the Maya lowlands: a preliminary report
Journal of Archaeological Science
(2010) How the Maya Built Their World
(1994)The evolution of plaster production and the growth of the Copan Maya state
Observaciones preliminares sobre el proceso de construccion en Piedras Negras
- et al.
A Late Classic lime-plaster kiln from the Maya centre of Copan, Honduras
Antiquity
(1996) - et al.
PN 5C: Excavaciones en el bano de vapor P-7
Monument building: some field experiments
Southwestern Journal of Anthropology
(1965)Excavaciones en el Templo de la Estructura J-4
- Hansen, E., 2000. Ancient Maya Burnt-Lime Technology: Cultural Implications of Technological Style. Unpublished Ph.D....
- et al.
Incipient Maya burnt-lime technology: characterization and chronological variations in Preclassic plaster, stucco, and mortar at Nakbe, Guatemala
Precolumbian Cements: A Study of the Calcareous Cements in Prehispanic Mesoamerican Building Construction
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