CALIFORNIA STATE UNIVERSITY, NORTHRIDGE
CERAMIC FIRING TECHNOLOGY " IN THE MOCHE VALLEY, PERU
A thesis submitted in partial satisfaction of the requirements for the degree of Master of Arts in Anthropology
by James Robert Szabo ~
January, 1977 1'"·--~-----.,-··--·---~----"'---· -· ------..-~~--~---·--"----~----~- .. , l
The Thesis of James Robert Szabo is approved,
Antonio Gilman (Date)
Paul L. K1.rk (Date)/
Carol .;r_.I Mackey Committee Chairperson
California State University, Northridge
ii ------~------,~------~
Dedicated to Janine
ACKNOWLEDGMENTS
I wish to express sincere appreciation to :carol Mackey. Her contributions to this work have been extensive. To mention just a few: She provided me the opportunity to participate in the Chan Chan .Moche Valley Project; secondly, she shared with me all :or the currently emerging unpublished articles from other scholars working on aspects of the Project; thirdly, for her constructive criticism and desire for this to be a worthy thesis; and finally, for the encouragement she offered when it was needed. I would also like to extend a special thank you to Diana Kamilli_, for her willingness to provide Carol and I with the results of her Thermoluminescence and X-ray Diffraction tests.
iii r--, --·~~1 I . They proved to be indispensable to the scope and quality of this study. To my wife Sherry, a deep appreciation for her typing and editing skills so freely offerred throughout the research, and for her patience and understanding.
___ Jl
iv TABLE OF CONTENTS Page ACKNOWLEDGMENTS iii LIST OF FIGURES vii ABSTRACT viii
INTRODUCTION 1 THE SAMPLE 4 DESCRIPTION OF THE CULTURE HISTORY IN THE MOCHE VALLEY 7 HYPOTHESES FOR ANALYSIS 13 Part I THE SIGNIFICANCE OF COLOR IN CERAMICS 16 COLOR AND TYPOLOGY 16 CAUSES OF COLOR IN POTTERY 19 CLAY FORMATION IN THE NORTH COAST VALLEYS OF PERU 24 BLACK CORES 28 COLOR VARIATION 31 COLOR ANALYSIS OF THE MOCHE VALLEY POTTERY 33 CONCLUSION 39
Part II APPARENT POROSITY 41 PHYSICAL PROPERTIES OF FIRED CLAY 43 POROSITY MEASUREMENTS 46 REFIRING TESTS AND POROSITY 48 CONCLUSIONS 52
v Page Part III PROBLEMS IN OPEN FIRING SITUATIONS · 56 FIRING ATMOSPHERES 59 FUELS 66 FUEL IN THE MOCHE VALLEY 71 PROCEDURES FOR OPEN FIRINGS 73 VARIATIONS IN FIRING PROCEDURES 77 NOTES ON.EXPERIMENTAL FIRING 81 CONCLUSION 94
Part IV SUMMARY OF CONCLUSIONS OF THE PROJECT 99
BIBLIOGRAPHY 106
APPENDIX 114 CHART 1 COLOR FIRING TEST 114 CHART 2 POROSITY MEASUREMENTS FOR THE MOCHE VALLEY SITE COLLECTIONS 118 CHART 3 FIRING TRENDS BY SITE COLLECTIONS FINEWARE 122 CHART 4 POROSITY AT 900°C 123 CHART 5 POROSITY AT 1150°C 124
l i l I I J
vi LIST OF FIGURES Figure Page 1 The Moche Valley sherd sample. 6 2 Moche Valley relative chronology. 8
3 Ceramic ~iring phases in the Viru and Moche Valleys. 12
4 Color e~~ects of iron oxides. 23 5 Varieties with black cores in the Moche Valley sample. 30
6 Predictable color objectives ~or the Moche Valley potters. 38
7 Properties o~ fired ceramics. 43 8 Apparent porosity formula. 46
9 Branch fuel ~iring. 85 10 Cow dung fuel firing. 86
11 Comparative experimental ~irings. 93 12a. Pottery of Firing #1. 95
12b. Firing #1 with. layer o~ branch ~uel in place. 95 13a. Firing #1 at completion. 96
13b. Oxidized vessel ~rom Firing #1. 96 14a. Firing #3. 97 14b. Firing #3. 97
15 Dark spout is evidence o~ incomplete oxidation. 98
I ---·~---,..1
vii ABSTRACT
CERAMIC FIRING TECHNOLOGY IN THE MOCHE VALLEY, PERU
by JAMES ROBERT SZABO
Master of Arts in Anthropology
In this work, the ceramic site collections of the Chan Chan - Moche Valley Project (excavation period, 1969 - 1975) are analyzed from the perspective of firing technology. Assuming that changes in the firing techniques reflect significant cultural changes, the emphasis has been placed upon the technological behavior of the Moche Valley potters. The firing of ceramics is performed within the cultural system and is an expression of traditional movements made by the potters that are as culturally significant as kinship groups or architectural styles. From this posture, physical attributes of the varieties relating to firing were examined.
viii The causes of color in earthenware clay are discussed in Part I. Color was found to be dependent upon iron oxides and carbonaceous impurities in the clay, Refiring tests conducted upon a representive sample from the total site collections indicate that the clay used is uniform throughout the various cultural periods. Variations in the color of pastes were found to be the result of the ability of potters of the various cultural periods to control the firing atmosphere. From this conclusion, typological catagories for color were developed, Porosity measurements were conducted in Part II of this study to provide comparative data on the ultimate firing ranges of the ceramics of individual
cultural units. A profile of the development of firing technology in the valley resulted from the analysis. The sequence of development is from 1) uncontrolled oxidation and reduction, to 2) controlled oxidation, and finally to 3) uncontrolled oxidation . , and controlled reduction. The peak of firing excellence was attained under controlled oxidation conditions. The later firing practices were examined to determine whether the uncontrolled firings indicate a decline in technology. The porosity comparisons
ix show that the later firing practices were accomplished at higher firing temperatures than the earlier cultural units. Evidence is presented to demonstrate that the technology of the potters of later cultural units was fully developed. As a culmination of the study of firing practices in the Moche Valley, firing experiments were accomplished. In Part III of this study, the relative difficulty of firing ceramics in open firing situations is discussed, Ethnographic descriptions of modern Peruvian potters is included to present the sequence of events in open firing situations. In the experiments, reduction and uncontrolled oxidation firings were found to be easier to accomplish than controlled oxidation firings. From the data obtained from the firings, it is evident that the ceramic technology of the Moche Valley continued to develop throughout the sequence of cultural units. The decline in the firing practices in the later cultural units is not a decline in technology, but rather the result of changes in pottery style. The functional aspects of the ceramics are discussed as an indication of why the later changes in quality occurred.
X CERAMIC FIRING TECHNOLOGY IN THE MOCHE VALLEY, PERU
INTRODUCTION
THE POTTERY FOUND IN MOST archaeological sites that were occupied by man after he began to farm and to settle on the land has changed very little in its appearance since it was fired and used. Although most exca vated vessels are broken or exist only as remnants in the form of one or more pot sherds, they serve as important evidences of the people who made and used them. Sherds are little affected by burial in the earth--they endure while metals corrode and disintegrate, and objects made of bark, wood or skin decay. Pottery preserves in its shape, decoration and physical properties a permanent though very fragmentary record of some of man's activities. Therefore, it must be studied intensively if the archaeolo gist is to reclaim from it all that is possible of the re6ord remaining in such objects, and of their associations with other materials, in his excavations of ancient villages and towns. If the mineralogical, physical and chemical properties of pottery are selectively determined in the light of the archaeolo gical problem being studied, information can be obtained about the raw materials selected and used by the potter, their treatment before being formed into pots, the manner of fashioning the vessels and of fir ing them, and perhaps the uses to which they were put. The role of the potter as the active and controlling agent in these procedures must be kept in mind, and _the function of his products in his community cannot be overlooked, We are concerned with the analytical data of products made by man, data which will help us better to
1 2
understand this man's culture. Each study increases our historical knowledge of technological developments in areas of the world where ceramic products have been manufactured through long periods of time (Matson 1963:592).
The comments of Matson on the value of studies in ceramic technology are characteristic of the new direction in analysis that contemporary archaeologists have taken towards more complete explanations of the cultural process. Archaeologists now have begun to demand more of excavated artifacts than the identification of their placement in time and space. The work of Anna Shepard (1956) on the various techniques of pottery analysis is the most comprehensive text for archaeologists. Early to recognize that the fabric of pottery held promise for new approaches to gathering data concerning artifact collections, her work has not yet been surpassed in scope. As well as her text on the scientific analysis of pottery, Shepard has developed an impressive bibliography in which she has used a broad variety of tests to extract valuable data from artifact collections casting new light on problems encountered at particular sites. A concise review of both optical and nuclear analytical methods is found in the work of D.P.S. Peacock (1970). 3
Lewis Binford (1962:218) elaborating upon the ideas of Leslie White, and Julian Steward, views the cultural experience as the vehicle in which man achieves a degree of efficiency in adapting to the natural environment. The physical resources and the ultimate potential of the environment are closely related to the technology that will be present in the adaptation process. The efforts of man to utilize and survive within the physical environment is achieved by means of his tools and social relationships which Binford recognizes as technology. Technology, when viewed from this perspective, is extremely valuable to the archaeologist. Considering the ecology of a site and the natural resources that man uses in the cultural framework to produce tools, demands that the archaeolo gist expand research designs and methodology in the analysis of artifact collections. Pottery analysis no longer can be limited to forming techniques, decoration, style, and typological relationships. Ceramic technology should also include the examination of the physical properties of the pottery as well as viewing the pottery as the product of a local manufacturing process. The production of ceramics occurs in a cultural framework, follows traditional methods of forming and firing, utilizes a local resource, and serves an important function in the culture. 4
r--·--~-~~ ------"'--~-~--"--~~~--"·-~·-"~---=-~----~-~~-~------~.,·-·--~·-·-··'" ; ... \More important than any other aspect of ceramic technology, \ j !it must be kept in mind that the technology is the direct result of a series of significant decisions that were :made by the potter and directed by what was considered to be appropriate to that cultural experience. The possibilities of analysis of an artifact collection seem to be endless when the number of available tests for ceramics are recognized. Many of these cannot be conducted in the field and require the assistance of physical scientists. The tests that are selected, therefore should be chosen upon their potential for producing data that will add new information about the culture by means of their technological activities. It is imperative that the question of what data is useful should precede the selection of the physical ·test for the pottery.
THE SAMPLE Ceramic artifacts comprising the sample for the present investigation are the result of field studies
• conducted by the Chan Chan - Moche Valley Pr~ject. Beginning in June 1969, and continuing to 1975, the Project focused upon settlements in the Moche Valley, ·with excavations and research financed by grants from the National Science Foundation, the National Geographic Society, and the Peabody Museum. The Project 5
>. is directed by Dr. Carol Mackey of California State University Northridge, and Dr. Michael Moseley of Harvard University. The pottery collected by excavations and surface collections represents the range of occupational sites from incipient agriculturalists to the period of Spanish conquest. Within the 4000 years of ceramic technology in the Meche Valley, the apex of urban development was achieved in the complex urban center of Chan Chan. The pre-colonial cultures of Peru are organized into a series of relative periods established by John Rowe, and the system is universally recognized by all Peruvian archaeologists. Changes in style of the finewares are the basis of the classification system and allow collections to be ordered, and therefore provide relative dating for the archaeological sites. The Rowe system also includes Horizon markers. Distinctive styles of pottery that are found over extensive areas of Peru are identified as Horizon styles. The Chan Chan·- Meche Valley collections were ordered into varieties, and by provenience and associations assigned to cultural units of the Rowe classification system. 6
THE NUMBER OF SHERD CULTURE VARIETIES STTES INITIAL CERAMIC PERIOD 6 Gramalote CUPISNIQUE 18 Caballo Muerto SALINAR 24 Cerro Arena, Huanchaco, Caballo Muerto GALLINAZO 22 Cerro Orejas, Cerro Blanco, Huanchaco MOCHE I - IV 20 Cerro Orejas, Moche Pyramids, The Moche Pyramid Site, Huanchaco lV!OCHE V 17 Galindo EARLY CHIMU 20 The Cemetery of Banderas, The Moche Pyramid Site MIDDLE CHIMU 26 Chan Chan, The Cemetery of Banderas, Milagro de San Jose LATE CHIMU 32 Chan Chan, Cerro Orejas, Caballo Muerto CHIMU - INCA Chan Chan, Cerro Orejas, Huanchaco, Caballo Muerto, Chiquitoy Viejo COLONIAL 21 Casa Madalengoitia (Partial of total collection).
Figure 1. The Moche Valley sherd sample. 7
The above description of the Moche Valley sherd sample corresponds to the Rowe chronology with some revisions as a result of the Chan Chan - Moche Valley Project excavations, (see Figure 2, following page) .
. DESCRIPTION OF THE CULTURE HISTORY IN THE MOCHE VALLEY In the Moche Valley, the Cupisnique and Moche V periods are important transitional periods of technolo gical and cultural change. Monumental constructions begin in the latter part of the Initial period along with movements of settlements from marine based shore line sites to interior settlements based on irrigation agriculture. During the Cupisnique period (Early Horizon), considerable monumental or corporate labor building activity occurred. The Early Intermediate period saw the development of extensive irrigational systems and large nucleated populations (Moseley and Mackey 1973:5). In general terms, the Early Intermediate period was a time of rapid developing technologies and the emergence of antecedents to urbanization in the Moche Valley. A stratified social organization is apparent evidenced by the monumental architecture, and specialized labor is present in the metalworking, pottery, and weaving crafts (Donnan and Mackey ms:l8). 8
REI.ATIVE MOCHE VALLEY CHRONOLOGY
Colonial Colonial Period
Chimu-Inca 1500 Late Horizon
late Chimu Intern1edla te Period 1000
Early Chi:r.u Middle Horizon * v
IV "C0 Moche III Early II Intermediate Period. I A.D.· Gallina:r;o !:l.lj.
Salinar
500
--
Early Horizon 1000 Cupisniquc
1500
** -· I:r:.i tial Gramalote Peri.od 2000
La 2C:OO Cumbre FTeceramic
Figure 2 3000 Chronological revisions1 Time Chart reference: ** (Pazorski, 1976) (Rowe and Menzel, 1967) * (Bawden, 1976) 9
The Middle Horizon in the Moche Valley was not a period of radical cultural change, However, the subsequent Late Intermediate period saw,the development of t.he urban center of Chan Chan and the peak of local population density for the valley. The high quality Meche I - IV oxidized redwares began to decline in the Moche V culture, and it is apparent that the potters were capable of producing finewares of higher quality, but chose not to do so. Uneven burnishing and surface color are common to ceramics at the Moche V site of Galindo (Bawden 1975:7). A general shift in the percentages of blackwares also occurred in the Moche V culture. A prevalence of partially reduced grey and brown pastes are noted by Garth Bawden at Galindo (1975:17). The general character of Galindo Moche V ceramics continues into the Chimu culture with notable increases in the occurrance of blackwares of a rather coarse appearance when compared to Moche I - IV finewares. Approximately 5% of Moche I - IV finewares are reduced, however, by Late Chimu times at least 30% of the finewares are blackware, (personal communication Carol Mackey), The Moche V transitional period between the Moche IV culture and the Early Chimu culture is of interest 10
r·~--.,.,..=.,·"'·'~~·= .. ~ ..... ~.... ,...---, ..-,-~,--,...... ,.,_ ...... "',..... =~-~=""'-~""·....,.-~"'"".... --~--~ ...... =~~-~~--.....-...... "'_'_~.._...,.,... ~.....,K~~-b:.>;-.2· ...- ....,... • .,.c.IJ.~'!> ...... , !technologically due to changes that are noted in the quality of the ceramics and methods of firing. The decline of craftsmanship in the Chimu ceramics was not 'expressed in metalworking, weaving and woodworking. There is evidence to assume that there was direct state control over the quantity, quality and nature of produced artifacts at Chan Chan (Topic 1976:52). Therefore, the quality of the Chimu ceramics is important culturally since other craft technologies continued to develop in the Chimu empire. Donnan (1965:128) identifies the Moche IV culture as the peak period of craftsmanship and excellence in ·pottery produced in the Viru Valley, Peru. The North Central Coast Valleys of Peru are relatively uniform in the stylistic divisions that were used by earlier archaeologists to establish chronologies and cultural sequences. The proximity of the Viru Valley to the adjacent Moche Valley to the north, accounts for a close correspondence in the cultural sequences for the two valleys. In the 1890's Max Uhle established a sequence for the cultural divisions apparent in the pottery collections of the Viru Valley. Further refinement of the culture sequence was accomplished by Duncan Strong and Clifford Evans (1952); James Ford (1949); Gordon Willey (1953); Wendell Bennett (1964); and others 11
participating in the Viru Valley Project of the middle nineteen forties. J.A. Bennyhoff (1952:233) elaborated upon Ford's typology of the plainwares of the Viru Valley, and argues quite convincingly that the history of ceramics in the Viru Valley should be viewed as consisting of three major periods of development based upon changes in firing technology. The earliest period is based upon evidence of ur1controlled oxidation in the Guanape~ culture. The second period encompasses the development of controlled oxidation and includes the Puerto Moorin, Gallinazo, and Huancaco cultures. A final firing period is based upon the shift to larger percentages of reduced blackwares
appearing in the Tornaval, La Plata, and Estero cultures and is called by Bennyhoff, the reduction period, (see Figure 3, following page). The distinction between the uncontrolled oxidation and controlled oxidation fir- ing periods is clearly a technological division based upon the ability of the potters to control the firing of the product. The difference between the controlled oxidation period and the reduction period is not a change in technology but rather a change in esthetics. Reduced blackwares are present in the pottery collections of Viru, from the Puerto Moorin culture to the Inca Horizon. The distinguishing basis for the recognition of a reduction period is the result of Ford's frequency 12
distributions identifying significantly larger percent ages of blackwares in the later cultures (Bennyhoff 1952:236). The cultural designations noted by Ford and utilized by Bennyhoff in the Viru typology correspond to the ceramics of the Moche Valley cultural divisions. The following comparative chart is provided to equate the cultural divisions utilized by Ford and Bennyhoff, and the designations utilized by the Chan Chan - Moche Valley Project.
Viru Valley Moche Valley Bennyhoff's Periods Pro,ject Pro,ject Guanape...... Gramalote Cupisnique uncontrolled oxidation
Puerto Moorin Salinar Gallinazo Gallinazo controlled oxidation Meche I - IV Moche I - IV
Huancaco Meche V
Tomaval Early Chimu
La Plata Chimu reduction Estero Chimu-Inca
Figure 3. Ceramic firing phases in the Viru and Moche Valleys. 13
HYPOTHESES FOR ANALYSIS The decline in craftsmanship and the changes in firing technology that began in the Meche V culture and continued throughout the subsequent Chimu culture raises several important questions worthy of investi gation. Hypotheses for the present study are not limited however to the Meche V ceramic collection. In order to provide a comprehensive perspective of the ceramic technology of the Meche Valley, all of the sherd varieties from the various excavations of the Chan Chan - Meche Valley Project were analyzed. 1. Is the range of color variation noted in the sample the result of firing atmosphere or variations in pastes? It is obvious that this working hypothesis relates to the differences between oxidized and reduced ceramics. However, the range of color represented in each site collection is quite broad. A group of oxidized redwares displays a wide variation in the color of pastes. Significant variations in paste color are noted for reduced blackwares as well. In Part I, the causes of color variation are discussed and the sample is analyzed for factors that contribute to the observed variations. 14
2. Does the general decline in craftsmanship noted in the ceramics of the Chimu culture reflect a decline in technology? Verification of this hypothesis depends upon demonstrating that technological advances did not occur in the ceramics of the Chimu culture, and that the potters could not achieve the superior oxidized finewares typical of the Moche culture, Comparative analysis of the degree of vitrification of the site collections are required to determine the extent to which changes are noted in the development of Moche Valley firing technology. Supporting data collected from measurements of relative firing temperatures is discussed in Part II of this study. 3. Do controlled oxidation firings require closer management of fuels and are they technologically more demanding than uncontrolled oxidation or controlled reduction in open firings? Part III of this study concentrates upon problems that potters must solve within their technological tradition to achieve predictable, uniform results. Several experimental fir ings were conducted and are discussed in relationship to the problem of evaluating the level of technical excellence that is apparent in the ceramics of the Moche I through Moche IV cultures in the Moche Valley. The degree of difficulty that is encountered in achieving an expected result in the framework of an 15
appropriate technology, is valuable to the archaeologist as well as the ethnographer. Although the firing conditions of pre-Columbian Peru can be simulated for analysis, the cultural tradition that the potters relied upon for their technological experience, of course, cannot. It is this very cultural tradition and technological experience that is the objective of all ceramic analysis, and as Binford (1962) noted, the aim of archaeology. Part 1 THE SIGNIFICANCE OF COLOR IN CERAMICS
COLOR AND TYPOLOGY The sorting of a collection of pottery sherds into comparable groups based upon the color of the sherds is probably one of the earliest typological distinc tions made by archeologists. Imposing limits upon the variations in a collection based upon color judgements occurs early in the analysis of a collection because the property of color is one of the easiest to measure and recognize in the sherds. Two aims of classification on the basis of color are important, 1) as a marker of variation in the collection to the typologist, and 2) as an indicator of firing atmosphere. The Munsell Color Chart, and color notations derived from its use, are nearly always found in contemporary site reports. Along with color notation, remarks referring to the firing environment are often also made. Terracotta redwares for example, may also be termed "oxidized", and blackwares may be identified as "reduced". The goal of the typologist when these distinctions are made, is to present the most complete description of the collection as possible.
·---·----·-----· --- 16 17
It is presumed that the complete and precise description affords other archaeologists that cannot view the collection personally, to be able to make reasonably accurate use of the sherds for comparative purposes through detailed notations. Within the scope of the present study, the perspective on typology has been consistent with the "mental template" attitude on the aims of classification. Further discussion on this position can be found in the work of Binford (1962), Bennyhoff (1952), and Deetz (1967). In keeping with this attitude on typology, distinctions should reflect the behavior of the potters within the cultural frame work of social influence and the technology at their disposal. Differences in color then would involve a change in activity for the potters that would permit them to produce a product that is different from some of the contemporary products, but the same as another significant group of products. It is the intentional alteration of the human activity that makes the typological distinction valid. In the area of color in pottery, it is nearly impossible to be certain that the typological distinctions we impose upon a collection are really significant alterations in human activities. We can be reasonably certain that it does when comparisons are made between redwares and blackwares, 18
however distinctions between graywares and blackwares may have no cultural significance. In order for this type of distinction to be valid, we must presume that a change in activity occurred either in the selection of the raw materials such as adding inclusions that affect color, or that a change in the way that the wares were fired occurred. Paste presents another series of problems to typologists in the analyzation of sherds. Some common forms of earthenware clays are found in areas that have no cultural or geographic relationships. Color even when determined by chemical composition in this case may have no cross-cultural value. Another problem within a site is encountered, when the same basic clay is used over long periods of time, and overlaps distinct cultural periods, as is the case in the Meche Valley. Further complicating the task for the typologists are the decorative techniques such as burnishing that have been independently discovered and utilized by a remarkably large number of cultural groups all over the world (Shepard 1956:347). The specialized techniques of surface decoration, form of vessel, and style have more typological validity due to the fact that we can be certain that these alterations were achieved by means of changes in human behavior. In general terms, the .more specialized 19
the trait is, the more validity it carries in a typological classification system (Shepard 1956a348). If the color is the distinction between two redwares for example, it may be a poor typological delineator since what we observe as a distinct difference in product may really be variations in color occurring repeatedly and without direct intention on the part of the potters. In the analysis of Mediterranean Neolithic pottery, two wares thought to be culturally distinct on the basis of a difference in the surface colors of gray and red, were later combined into one ware. The basis for this typological judgement was that the sherds were capable of interchanges in color through the action of refiring. Apparently, the changes in color were caused by variation in final firing atmosphere but not intended by the potters, and therefore, not typologically significant (Biek 1963a73). Color is significant as a typological distinction if it can be traced to differences in the raw materials or to changes that occur through the application of technological behavior in firing methods.
CAUSES OF COLOR IN POTTERY The two main causes of color in pottery are the chemical composition of the clay and the conditions 20
under which the pottery was fired. Anna Shepard (1957:16) notes that the main chemical constituents affecting color are the iron compounds present as impurities in surface clays, and organic matter present in the clay through the natural formation of the clay beds. Earthenware clays that have high percentages of iron compounds produce a possible spectrum of color upon firing from buff and yellow to reds and browns when fired in an oxidizing environment. The same clay can produce grays and blacks if smudged. Carbonaceous matter in the clay and the proximity to the fuel both are conducive to smudging, Grays and blacks are also possible through reduction firings. Therefore, a clay that we catagorize as red earthenware has the potential chemically to produce buff, yellow, red, brown, gray or black pottery (Shepard 1957:16). W,G. Lawrence (1972:35) describes common brick clays or earthenware clays, as containing varying degrees of the clay minerals, chlorite, illite, kaolinite, quartz, mica, and iron oxide compounds. The carbonaceous matter in the clay is conducive to reduction. The important iron oxides present are magnetite Fe304, and hematite Fe2o3. Both iron compounds react similarly in firing to produce the 21
:common range of color possibilities for earthenware 'clays, Shepard, notes that carbonaceous matter in clay when not fully oxidized, produces gray, gray-browns, i/ and buff colors. The clearest color range occurs at approximately Soooc if the firing atmosphere affords complete oxidation. When fired to l000°C, ferric oxides that cause the bright reds of earthenwares begin to lose oxygen and the colors become darker. As vitrification commences, the reds become dark reds and the ferric form of iron (Fe203 or Fe304) changes to a ferrous state (feO) as the oxygen molecules are released. Ferrous iron acts as a strong fluxing agent and as vitrification occurs the iron constituents of the clay are particularly active chemicals. At 1300°C ferric oxides are not chemically present. Only ferrous states of iron compounds are possible at this temperature range, however, these temperatures are impossible in open firing situations, and rarely are temperatures in excess of l000°C reached (Shepard 1957:23). Several variables must be controlled in order for the clearest red colors to occur through the action of the iron oxides in firing. Color variation can occur through the position of the pottery in the firing. A large pile of pots will normally show variation 22
in surface color depending upon the placement of a particular pot in the stack, the proximity to the fuels, and the degree in which free oxygen could reach all surfaces of the pottery. Interior surfaces of spouted vessels, and bowls that are fired in inverted positions frequently are reduced due to lack of free available oxygen during firing. Temperature also varies considerably in a large firing, and certainly independent firings vary from each other in open firing conditions. Duration of heat as well as the maximum temperatures reached also affect the final color of the wares (Franken 1974:66). Carbonaceous matter must be completely eliminated prior to the completion of the firing; this is achieved by time as well as temperatures reached in firing. Even when adequate heat is available in a firing to oxidize redwares, if the firing time is too short, black cores result and appear as a dark, dense zone sandwiched between two layers of red surface colors in sherd cross-sections.
The iron oxide hematite (Fe2o3 ) is red in color in raw clay and is unchanged in an oxidizing firing environment. The percentage of this ferric oxide has less final effect upon color than the size of grains of the oxide. Magnetite (Fe304) is gray in the raw clay and changes form from ferro-ferric oxide to ferric oxide (hematite, Fe 2o3) if fully oxidized 2.3 and carbonaceous impurities are completely eliminated.
In reduction firings, ferric oxides (Fe2o3) become ferro-ferric (Fe3o4) oxide or ferrous oxide (FeO) and cause the clay to fire to gray. Red clay sherds there- fore, are the result of oxidation upon hematite (ferric oxide), or the conversion of magetite (ferro-ferric oxide) to hematite in the presence of adequate heat and free oxygen. If insufficient oxygen is present hematite may change to magnetite and produce graywares; or if the iron oxide present is magnetite and it is prevented from oxidizing, it will remain the same or further reduce to produce grayware. If reduction is very strong, ferrous oxide (FeO) is produced which causes the blacks of fully reduced earthenwares (Shepard 1956:104).
raw cla:y oxidation mild strong reduction reduction
Hematite Fe2o3 Fe2o3 Fe~04 FeO red red gr y black
Magnetite Fe304 Fe20.3 Fe3o4 FeO gray red gray black Ferrous absent absent FeO FeO Oxide dark gray black to black
Figure 4. Color effects of iron oxides. 24
It is worth noting that the chemical actions of oxidation and reduction are not necessarily as simple as the previous diagram would suggest. Although hematite and magnetite are the common iron compounds found in clays, they are not the only iron compounds present. Iron is also present in clays in sulphides, carbonates, hydroxides and silicates. At various stages of firing each compound is capable of providing iron or oxygen molecules that combine with the major coloring oxides of hematite and magnetite (Lawrence 1972:35). In its final form, however, it is the effects of these two principal iron oxides and their conversions to ferrous oxide that is responsible for what we observe as color in fired pottery. The entire color range of earthenware pottery, buff, yellow, orange, red, brown, gray, and black are all due to the effects of iron oxides in the clay and the technological act of firing the pottery.
CLAY FORMATION IN THE NORTH COAST VALLEYS OF PERU R.E. Grim (1962:503-518) in his work on clay mineralogy presents a concise description of the natural process of the formation of clays. Clays are formed through the weathering of parent igneous rock. The·climate of the region is the primary determining factor affecting the characteristics of the clays 25
r·--_...... ,...._,. .. =-=""'~"'·' .... .--.....:..·=-'"""""~"'""""~""~~=..--""~--"-=-·--··~-·~,._~--=---~...... ~-"""""'-"'--.....,.,.""" ...... ,._,...... _...,."","""~ i i )that are formed in particular localities. All clays contain the prlmary clay chemicals of alumina and silica in relatively large proportions. Alumina and lsilica are the end products of the weathering process but deposits of these clay minerals in a pure state are very rare. Usually a clay deposit includes these ·minerals and various mineral compounds considered to be impurities, as well as a wide variety of alumina silica compounds in intermediate stages of decomposition. The formation of a clay deposit is a continuous cycle of decomposition of rock dependent upon moisture passing through the soil which leaches out the soluble mineral compounds and impurities. The purest clay deposits would then be expected to occur in areas of heavy rainfall and continuous available moisture. The iron compounds that affect color in clay are water soluble therefore, the purest clays are white. In the North Coast Valleys of Peru, the desert climate is nearly rainless. The lack of moisture and soil leaching processes account for the high iron oxide impurities in local clays and consequently the characteristic red-orange color of well-oxidized pottery. Vegetation in the North Coast Valleys of Peru, is comprised of sparse shrub and grass covered soils 26
typical of arid to temperate regions. Gray desert soils are found in this region due to the absence of a cover of vegetation and lack of downward leaching of the soil. Carbonates, salts, and organic materials are concentrated in the upper zones of the soils (Grim 1962a514). The soil is classified as pedalfer, which is described as gray or red desertic soil, having a tendency for alumina and ferric iron to accumulate near the surface (Grim 1962:510). In arid regions, when potassium and magnesium are present in the parent rock and weathering is limited by rainfall, the clays that will be formed will be primarily composed of illite and smectite clay minerals. These clay mineral compounds include alumina, silica, potassium and magnesium. If the magnesium components of the parent rock are in low concentrations then only the illite minerals will be present, Illite clays are called mica-bearing clays since the formation of illite clay also affords favorable conditions for the formation of mica from the alumina, silica, potassium, magnesium, iron, and lithium minerals that are naturally present in pedalfer soils (Grim 1962:516- 518), Two major illite clay mineral compounds, important to the Moche Valley ceramics, are muscovite and biotite. 27
r·-,~-·-·-"----,~-~.. ~·-----~··------·~-·---~--.~---~~·~·J··. ' In her unpublished paper on the clay mineralogy of the Moche Valley ceramics, Diana Kamilli (n.d. :ms) notes that the results of thin-section optical analysis, and x-ray diffraction studies indicated that every sherd in her sample was composed of biotite as the dominate clay mineral, and half of the sample contained muscovite as well. The sample was composed of sherds spanning nearly the entire cultural history of the valley, therefore, these minerals can be viewed as characteristic of the Moche Valley clays, Due to the persistent climate conditions, the clay composition of the valley shows no significant alteration through the various cultural periods. Anna Shepard (1954:127) was one of the earliest archaeologists to use clay mineralogical studies to identify trade pottery in her study of the ceramics of Pecos, New Mexico. The nuclear methods of paste analysis including Neutron Activation, X-ray Diffrac tion, and the Mossbauer Effect have become important resources for the archaeologist and have been generally replacing the earlier techniques of petrological studies and spectrographic analysis when clay mineral content information is desired to test hypotheses about cultural units. Within this paper the local clay mineralogy of the Moche Valley is not 28
provide data to reconstruct the ceramic firing technology of the valley.
BLACK CORES In the early stages of firing pottery, in the temperature range of 350°C - 700°C, the principal change which occurs is the elimination of organic, carbonaceous impurities in the clay. With clays that have high percentages of iron oxides, oxygen must be available to combine with the carbon produced from the organic impurities and be released during combustion as co2 gas. Complete oxidation follows the elimination of the carbonaceous matter at temperatures between 70ooc and 900°C and the result is a clear, bright red color on the surface and throughout the paste. If insufficient oxygen is available during the period of elimination of carbonaceous matter, the necessary oxygen for the production of co2 gas will be provided by the iron oxides, hematite Fe2o3 and magnetite Fe3o4, which causes them to be reduced to ferrous iron oxide FeO. ~he available oxygen moves from the core to the outer vessel surfaces which causes the sandwich effect of black cores. FeO in the interior of the paste acts as a powerful fluxing agent, which 29
1972:122}. Several factors may be responsible for the occurrance of black cores. First, the firing time may have been too short for the complete elimination of the carbonaceous matter; second, the temperatures reached in the open pit firing may have been too low for complete oxidation; and third, insufficient oxygen may have been caused by a poor draft (Shepard 1956:104). Black cores indicate the oxidation firing was poorly managed, and sherds with dark cores should not be recognized as independent wares. When refired with sufficient oxygen, the black core is eliminated (Franken 1974:65). In terms of the firing technology of a cultural group, however, black cores are important aspects of technology and should be recognized and noted when they appear in artifact collections. 30
TOTAL lj_ OF CULTURE VARIETIES APPROXIMATE VARIETIES WITH BLACK DATE IN GROUP CORE_ {ROWE CHART PAGE 8)
6 GRAMALOTE CA 1 2100 BC - 1700 BC 24 SALINAR s 34 400 BC - 150 BC SALINAR SG 24 22 GALLINAZO G 19 150 BC - 50 AD GALLINAZO G 20 GALLINAZO G 24 57 MOCI-IE 4 De. 50 AD - 900 AD 26 MIDDLE CHIMU cc 27 900 AD- 1476 AD ·LATE CHIMU
Figure 5. Varieties with black cores in the Moche Valley sample.
The first six varieties precede the Moche cultural
I period in the valley. I/ Excellence of oxidation and control of all aspects of ceramic technology has long been recognized as characteristic of the Moche period (Lanning 1967:122). Black cores are absent from the Moche sherds indicating that during this period knowledge of the complete control of firing was present. This does not presume that firing accidents did not occur, for in fact, any deviation ' from the perfect oxidation red-orange color of the Moche Valley clay can be viewed as accidents of firing. When firing technology reaches the point 31
that firings can be closely controlled for color and complete oxidation, all deviations from the clearest color in the sample for a cultural unit are accidental (Shepard 1956sll2).
COLOR VARIATION A single clay has the potential to produce a range in color. The degree to which potters could consistently produce pottery with uniform color dis~ closes the level of technological control that was achieved in the original firing (Shepard 1956:112). The data from the sample presents the opportunity to reconstruct the conditions under which the pottery was fired and therefore is an index of the technological behavior of the potters in the manufacture of the product. For example, black cores are clear indicators of the degree of success that was achieved in controlling the oxidation of the wares; furthermore, surface color and core color indicates the potter's capability of controlling the firing atmosphere. Descriptions of the range of possible colors in a collection and the deviation from the clearest red sherd in the sample, presents data that reflects the extent to which the potters achieved technological con trol over the product. 32
A single, local clay resource will vary in color upon firing depending upon the final firing atmosphere. Uneven vessel color is caused by fluctuations in the firing atmosphere or proximity to fuels under combustion. The firing atmosphere is always a mixture of reduction and oxidation gases dependent upon the fuels that are used, the time they are added to the fire, and the degree of available oxygen. As the fuels ignite reducing gases are present, but they may have no effect upon color due to the low temperature of the fire. As the fuel burns, carbonaceous matter will be eliminated if a good draft providing available oxygen is present. If no new fuel is added and the temperature reaches 700°C - 900°C with adequate draft, complete oxidation and clear, bright colors result from iron bearing clays. If new fuel is added, reducing gases are again present and at higher temperatures may cause reduction color effects (Shepard 1956:216). Iron bearing clays that result in gray colors have been subjected to one of the following firing conditions. Carbonaceous matter may have not been entirely eliminated from the clay, or insufficient oxygen was present during the firing. Gray colors are also caused by direct contact of the pottery with the firing fuels (smudging), and is often 33
~~-~~,_..,..,...... ,.,.__..,.,....,._....,.______C'""""""""'"""~----·-~--,- ... ,,,,,.,.. ,.~=-~~-~ ! . mistakenly identified as "hearth-blackened". It is not unusual to place pottery to be fired on a bed of twigs which later in the firing process may cause carbon deposits to appear on the bottom of the pots. A final cause of graywares is reduction firing; an intentional management of the firing to produce grays and blacks. Frequently, reduced pottery is smudged as well as reduced, but it is important to recognize that reduction is a chemical reaction involving oxygen and the iron oxides present in the clay, whereas smudging is a surface deposit of free carbon on the pottery (Shepard 1956a219).
COLOR ANALYSIS OF THE MOCHE VALLEY POTTERY One method of analyzing color variation in a pottery collection is to note the degree of variations in pastes. This involves the refiring of a group of excavated sherds selected upon the basis of the range of colors that are noted. By standardizing the firing temperature, fuels, and draft, the collection will be comparable upon the basis of color that results from the refiring. The data provided by refiring tests enables the pottery analyst the opportunity to recognize the variation in clay mineral composition by means of the color range that occurs when the sherds are subjected to identical firing conditions. A sample 34
is refired in an electric kiln at 900°C. This insures that sufficient oxygen is present for complete ~xidation, and holding that temperature for a sufficient period of time insures complete oxidation. The 900°C temperature is suggested, as this is well into the optimum oxidation firing range, but it is not high enough to cause overfiring or vitrification of common iron bearing surface clays (Franken 1974a65). A collection of 33 sherds from the Moche Valley excavations were selected upon the basis of the color range present on the inner and outer surfaces and the core. A complete description of the controls of the firing atmosphere and time of firing is presented in Part II of this paper, in the section titled "REFIRING TESTS AND POROSITY". Notations of color were based upon the Munsell Soil Color Charts before and after the refiring tests, (see CHART 1, Appendix). Prior to the test, the she~ds selected represented the entire .range of possible colors from iron oxide compounds. Several sherds had black cores; Gramalote CAl; Salinar S34, SG24; and Gallinazo G24. At least 16 sherds have been described as oxidized or partially oxidized redwares, and the remaining 17 sherds as reduced or partially reduced gray or blackwares. The total range of colors for Moche Valley pottery has been 3.5
f"'-.,.,.~'"'""""""'"""'-"•"""~~~~-,.,..=...... ,.,~=--...... --- .,...... _ .. ~-~=--,_,.,...... __"'"'~-· =· - .... --~-·------~or=&.,_,~--""_._ ...... _.~,~><·=---=·r.<""'- ' constricted into two basic wares on the basis of color; redwares and blackwares. If the classifications of redwares and blackwares are correct, then the assumption follows that the potters were attempting with each firing to produce clear, bright reds or blacks depending upon how they managed the firing atmosphere. All variations of color that appear in various sherds are then explainable by two possibilities. Either the clays varied in mineral content which would produce different color effects upon firing under identical conditions, or the range in color is the result of firing accidents and not the intention of the potters. The results of the refiring test show that the color of the sherds fired under optimum oxidation conditions does not vary significantly for the entire sample. Thirty-one sherds of the entire thirty-three sherd sample refired within the range of a Munsell color designated 2.5 YR 4/6 (red) through 2.5 YR 6/8 (light red). On the Munsell Color Chart, this range of color corresponds to well-oxidized red pastes. The variation between 2.5 YR 4/6 and 2.5 YR 6/8 is very slight especially for a sample as broad as the Moche Valley collection which spans 4000 years of ceramic products. Two sherds varied from this range of color; Meche M20, and Salinar S)J. Both sherds were originally reduced and refired respectively to 36
f...... ,...~ .. ..,...... ,~.,.,.,.--:o control the firing atmosphere to achieve a predictable color for incompletely oxidized or partially reduced pottery, we can postulate that the color objectives of the potters of the Moche Valley were to produce only two possible colors; redware and blackware. John Topic {1970:86) in the examination of ceramics excavated at Chan Chan, speculates that the wide color range present is due to incomplete oxidation firing. Garth Bawden (1975:12) also noted the color variations in Moche V ceramics at Galindo, and attributes the causes to uneven reduction firings. In the same work, Bawden also identifies the Moche V inventory as consisting of three major groups: reduced fired blackwares, oxidized redwares, and incompletely reduced grays and browns (Bawden 1975:5). A slight variation in the color is possible by burnishing the partially dry pottery. Burnishing polishes the surface of the vessel and constricts the clay particles into a dense layer which, upon firing, adds a sheen to the pottery and darkens the color. This variation in surface is predictable and therefore allows for four possible colors for the potters in the valley. 38 REDWARE BURNISHED oxidized matte shiny red dark red BLACKWARE reduced matte shiny black black Figure 6. Predictable color objectives for the Moche Valley potters. For typological classifications, the above four catagories of color should be recognized for the Moche Valley excavations. Surface decoration, vessel size and shape, tempering materials, and forming processes are valid catagories for grouping the collection into finer comparable units. Firing technology is expressed in the sherds by color analysis, porosity, and recognition of the control of the firing atmosphere. The Moche Valley ceramics have proven to be an ideal collection upon which to apply analytical tests concerning the firing technology. The stable mineral content of the clay resource and the long sequence of habitation sites in the valley provide both natural restrictions of possible variables in the pottery, and the opportunity to trace technological advances through time. ---' • ~_,~._... .,__,_,_._ _,.._.,.-...... ,- ..,.._ _ _..., .•. ..,..,~-·-•'-"•u-•.-.----.-.•--'•..,•q"'-._~_..,. .. ___....,__...., ____ ~••__,• __~.-~---..""""""~--~--_,...... _M••-•,__,.~~~·~___,....., __.;; ' 39 CONCLUSION Returning to the original hypothesis for the analysis of color, it was stateda "Is the range of color variation noted in the sample the result of firing atmosphere and not variations in pastes?" (page 13). The sample selected for the refiring test included representative sherds from each site collection of the Chan Chan - Moche Valley Project. The range of time represented by the sample is from 1900 B.C. to 1800 A.D., and includes sherds from all of the cultural divisions. Under controlled oxidation conditions, the sample refired to a uniform red-orange color with no appreciable deviation. The evidence indicates that the variations noted in the original larger sample are unintentional deviations from the two basic color objectives of redware and blackware. The primary causes of the variations are due to firing atmospheres and not the result of differences in the basic constituents in the pastes. Consequently, paste color in the Moche Valley ceramics is the result of the controls that were imposed by the potters on the firing conditions. In terms of the evolution of ceramic technology in the cultures of the Moche Valley, the analysis 40 of firing methods and their changes throughout time are of major importance. The ability of the Moche I - IV potters to produce oxidized redwares of very high quality represents a tradition of ceramic technology expressed in the behavior of the potters. The utilization of the resources, the actions of the craftsmen, and the relationship of the craftsmen to the cultural framework, indicates the degree of efficiency that the culture possessed in adapting to the natural environment, Part II APPARENT POROSITY Laboratory analysis of site collections rarely include a measure of the porosity of sherds. Studies· nearly always are entered upon the physical character istics of hardness, density, strength, color, temper, and sherd thickness. Adventures into the less obvious pottery traits center around mineralogical analysis by means of petrological studies or nuclear specto graphic studies and trait analysis. It is important to note that any descriptive characteristic of a site collection has potential analytical value for the archaeologist. Rarely, however, can every physical trait be described, nor should they be since the expenditure of labor would be prohibitive. A physical descriptive pottery trait should be measured when that trait and its changes through time within the site would disclose new data applicable to the analysis of behavior on the site. Anna Shepard (1956:125) used porosity as a comparative tool on the Pecos, New Mexico collection in 1942. Conclusions that were drawn from the test could not have been easily extracted by another method of analysis. Porosity is a rather hidden 41 42 j""'-""-·. ...-..v~· _._._..,...,...._..,...,._,.,._.,.__~., ! . ~ characteristic of pottery along with strength and density. With due considerations, concerning the 'nature of the clays to be tested, porosity is a good !indicator of the degree to which a sherd has been . fired. Porosity measures the pore space that is capable of being occupied by water in a sherd. True porosity is a measure of the exact volume of the pores. Apparent porosity is the relative measure of pore space, or that measure which under controlled conditions produces identical results. Apparent porosity is slightly lower than true porosity; however, it is the most useful and easiest test to apply to pre-wheel produced ceramics. Ideally the porosity of earthenware clay decreases in a steady curve as vitrification is reached in firing (Rhodes 1957:200). If carbonaceous matter is present in an appreciable degree, then the porosity increases nearing vitrification, and decreases . rapidly as vitrification commences (Shepard 1956•223). Carbonaceous matter in the surface clays common to · the Moche Valley has a significant effect upon the . porosity of the wares. The origin of the vegetable matter is apparently the stream beds in which the iron bearing clay beds were formed as secondary deposits • caused by moving water (Rhodes 1957•10). ~~-.a..-.~=:..-~ ...... --,----~-..--,.,-~~ ...-·-· ,..--..-~-~-~--~·~- •...... _...... ,_~_.1 l Although porosity alone cannot be used to determine the firing temperature of pottery, it can be used to compare the varieties of a collection to discover whether the control of firing variables and consequently ceramic technology, was continuously advancing throughout time. As a relative measure, porosity is an indicator of density, strength, and hardness in the ceramic product whenever comparisons are made within a sample of consistently uniform clay composition. PHYSICAL PROPERTIES OF FIRED CLAY Porosity, hardness, density, and strength are physical properties of fired clay that are directly related to one or all of the following characteristics of ceramic technology& the mineral content and nature of the raw clay, tempering materials, and the degree of maturity reached in firing. PROPERTY FACTORS AFFECTING THE PROPERTIES type of clay temper firing maturity porosity X X X hardness X X density X X X strength X X X Figure 7. Properties of fired ceramics. The three variables influencing these properties must be considered in order to draw inferences from descriptive measurements taken from the sample. The concerted changes that the raw materials undergo in manufacture and firing in any one property can be used to establish relative comparative data. Ideally, all measurements enhance the description of the artifacts; however, any one area can be utilized to compare varieties within the sample if the variables can be limited. The choice of porosity to discover the degree of firing maturity of a ceramic variety within the Moche Valley sample requires that the variables of the mineral content of the varieties and the effects of tempering materials be controlled. Tempering materials of the Moche ceramics are generally of two types. Quartz is the primary tempering material whenever fine grained tempers are present, and rock fragments or fine grained volcanic porphyry pebbles occur in coarse grained tempers. The quartz tempering materials are always present apparently due to the conditions under which the clay deposits were formed in river bottoms and stream beds. Fine grained quartz tempers are characteristic of the finewares of the Moche Valley. Coarser grained tempers are present in the utilitarian wares and are directly associated with the thickness of the sherds and the 45 ,,_,"~~-~-"'---~-=-..... -·-· -·----·~-~-~-·--·~~-----~------~·---~-----~-"~·~--. ! ultimate vessel size. The materials used and their proportions are quite consistent and characteristic of the ceramics of the valley despite the fact that the sample represents several different cultural periods and spans a considerable period of human habitation in the valley (Kamilli n.d.ams). The effects of tempering materials upon porosity are dependent upon the type of temper and particle size. With this data we can group the Moche Valley ceramics into two broad groups for comparison; the ceramics with quartz granules less than 2 mm. in size are used in finewares and ceramics with quartz or granite granules larger than 2 mm. are used in utilitarian wares. The fineware tempers have little effect on porosity. The coarse grained tempers of the utilitarian wares retard the vitrification of the clay and therefore cause greater porosity to be apparent than one would measure in a sherd of a fineware vessel that was fired to the same degree of maturity· (Shepard 1954:130). The mineral content of the clay of the Moche Valley ceramics was analyzed by Diana Kamilli in her unpublished preliminary work with thermoluminscence. She has shown that the chemical composition of the clay and tempers show slight variation through time. 46 lr·~·---~--·,.·--~----·--··-=·-·--· -·------~---··---~~--·-· ------~~~------n-,. The uniform clay composition and tempers of the Moche Valley sample indicated in the findings of Diana Kamilli (n.d.:ms) are important to the porosity studies. Returning to Figure 7 (page 43), the three factors affecting porosity wereJ 1) the type of clay, 2) tempering materials, and 3) firing maturity. If the clays and tempers are relatively uniform as they are in the Moche Valley sample, porosity measurements will indicate the degree of maturity for each variety in the sample. We can postulate that as the ceramic technology in the valley was advancing the potters had more control over the firing techniques, and therefore were capable of achieving a uniform well-fired product. POROSITY MEASUREMENTS Anna Shepard (1971:127) cites the procedures established by the American Ceramic Society as the standard test for porosity, Archeologists have adopted this formula as the universal testing . procedure when porosity measurements are required. Wet sherd, weight in grams---Dry sherd, weight in grams X 100 volume in cubic centimeters Figure 8. Apparent porosity formula. . 'i ··-·-·~···--~"'"--..-~---.- ... -·~-~=·~ ...... ,_..,.._ ...... _..,._.,...,._.._,.,_...... , __.. , ______,_,.._~---·------~ .. ,....._,; . . ,4·~--....--..,.--....,...... __,.,_~,_ ...-~--- ...... -~--..,..----~--~-___..,....._.. _____ ...,~.~- .."""'·'"'3>0<~·--~- ... "'='-<-"h=~ ' 1. The sherd is weighed dry with a beam scale capable of accurate measurement to .01 grams. 2. The sample is boiled in distilled water for two (2) hours to achieve maximum water absorbtion, 3. After cooling to room temperature the sherd is wiped lightly to remove surface water and re-weighed. 4. Volume measurements are taken of the wet sherd with an overflow volumeter. 5. The displaced water is weighed in grams due to the fact that one c.c. of water is equal to one gram of water by weight. 6. Calculations resulting from the formula are presented in percentages of water as a ratio of the volume of the sherd. The Moche Valley ceramic sample includes eleven site collections representing all of the major cultural phases of habitation in the valley from the first appearance of pottery to the Colonial period, All varieties in each site collection were measured and porosity profiles were established (see CHART 2, Appendix). The average percentage of porosity for the utilitarian wares was consistently between 20 and 40 percent. The finewares varied considerably with porosity increasing steadily from the earliest site, Gramal9te, to the Chan Chan site collection. A reversal in this trend occurs with the finewares from the Chiquitoy Viejo site collection as these ' ••"L<• ••<~·•»"·'~··'-~--~.-.,-.....~_.,.,_..,,~_.,._,.,.., .. ,,~--__,~-•.-.--~ ...- •. -~~~-~-..,.._...... ,._~~a-~-...... -•-..,_...,.,...~..,...~ sherds show a decrease in porosity (see CHART 3, Appendix). The discussion of why the reversal in porosity occurred is found on page 50. The trends noted in the finewares indicate that the finewares are the preferred sherds to secure data on firing technology. REFIRING TESTS AND POROSITY A collection of sherds was selected for color variation from each of the eleven site collections as a test group for comparisons. Three varieties were taken from each collection and a sample of 33 sherds were refired and measured. The purpose of the refiring test is to note the changes in porosity that can be observed from a sample which has been fired to controlled conditions of oxidation and temperature. Franken (1974a65) suggests the sample be refired to a temperature that exceeds the original temperature for the sherds. We can assume that 900°C was reached in the open firings used in the Moche Valley. Anna Shepard (1954:83) is certain that l000°C is a safe refiring temperature for a standard test group. The collection was refired to 900°C and held at that temperature for one hour. The firing was accomplished in a front loading electric kiln capable ~~9 i'-~., ...... ,_.. .. ~,._-----~..... - ...... ,,.,,__ _...~..._.~ ...... ~=-·-~-_...- ...... """'_~-·.. -"'~~~-~-~~"""""-"""'" I i of precise control of temperature and oxidizing l l environment. The sherd sample was arranged on tile firing racks, each sherd standing on edge to insure that the entire collection was exposed to the same firing conditions. The maximum temperature for the refired sample was reached in two hours. After the cooled sample was removed from the kiln, porosity measurements were again taken (see CHART 4, Appendix). ~herds from the Cupisnique culture through the Moche V culture showed a marked increase in porosity. From the Early Chimu culture to the Colonial period increases in porosity were significantly lower, and nearly half of the sample in these site collections show a decrease in porosity. Interpretation of this data requires an explanation of the changes that occur in carbonaceous clays at various firing temperatures. Lawrence (1972tll3) conducted experimental firing tests under laboratory conditions and noted the changes that the clay bodies undergo at the pre-vitrification stages. The oxidation period occurs between 300°C and 700°C. At this stage of firing the carbonaceous matter in the clay is being oxidized and eventually .removed. As higher temperatures are achieved, the clay body shows an increase in porosity due to the pore space now present as a result of removal of the vegetable .. ' '·· --~.~--·-···•'-c·--·~"'--·''-'"•~•· ...... ,...... ~.--~- ... ~·-""'-'~"""~------··,_..,.. •. _--...... _...... ______....,...... -~~-·---~-.. ~.... -·-----"·-·-~"''=-J 50 ,--~·-"'-'"'''""""'~---·------·----·-·----. -·------~---~ ... ~---"'-=>...... <>.·; i ; I ! impurities. The major increases in porosity occur in the range of 500°C - 750°C. The porosity level remains constant to l000°C and then decreases rapidly as vitrification commences. The 900°C temperature achieved in the refiring tests is well into the oxidation range and indicates that the increase in porosity is due to the complete oxidation of the sample as well as an exceeded firing point over the original firing. From the Cupisnique culture to the Moche V culture, the increase in porosity indicates that firings were below 90ooc and show an increase in the ability of the Moche Valley potters to achieve nearly perfect oxidation in the Moche culture. From the Early Chimu culture to the Chimu - Inca culture, the pottery is fired to the maximum temperatures that can be reached in open firing conditions. As clay nears the vitrification point, a decrease in porosity occurs. Ceramics later than the Early Chimu culture display both increases and decreases in porosity indicating that vitrification for the Moche Valley common red clay is near the 900°C temperature, and the potters of the Chimu and Chimu - Inca cultures in the valley were firing at a higher temperature range (see CHART 4, Appendix). "~·"-'""'·""-~~---~~·~·-~=·~--=_,...... ,._,_~..._.,,.~"""""'"""------...... ,,-.~--·--.-..,..,.~..,...--.•...-...--.,...,._.._.._._-.""" ...-..~._..._._a~"".------··--.---.,-...,~.,,..,.,....,. •...-. .. -..~~"'-"-~••---..-~""--"~•·.,.,..~.; ' 51 Refiring tests conducted on the sample to 115ooc indicates that vitrification is occurring at this temperature. Conditions of stacking the kiln, and controls of firing environment were repeated for the second refiring. The maximum temperature of 1150°C was reached in four hours. The kiln was held at this temperature for 30 minutes. The sherds show definite signs of overfiring and increased density (see CHART 5, Appendix). Marked shrinkage is evident' in all but the Initial period sherds. More than half of the sherds show signs of distortion and collapse. Shrinkage, distortion and collapse are indicators that the firing temperature exceeded the vitrification limits for the particular clay (Rhodes 1957&204). The maturity range for the clay is between 900°C and l000°C or what the contemporary ceramic industry recognizes as "cone 06 low-fire red clay". In porosity measurements a vitrified clay decreases in porosity as the pore spaces in the clay are filled with liquid matter. The body also shrinks in volume (Shepard 1954:126). A comparison of the 900°C firing test and the 1150°C test indicate that with the exception of the Gramalote sample, all sherds are vitrifying. 52 ------CONCLUSIONS Data from the comparisons of porosity of original firing state, refiring at 900°C, and refiring at 1150°C, indicate that during the interval between the Early and Middle Horizons, the potters of the Mocha Valley were firing in the optimum firing range for the clay resource at their disposal and the temperature range possible with open firing conditions. During the interval between the Middle and Late Horizons, the potters were firing at higher temperatures closer to the vitrification point of the clay but still within the possible attainable temperatures of open firing, 900°C. In terms of technology, this change in firing indicates that the excellence of oxidation that is characteristic of the Mocha ceramics was achieved at lower firing temperatures than the blackwares of the Chimu culture. The original hypothesis that the decline in craftsmanship noted in the ceramics of the Chimu culture does not reflect a-decline in technology is evident particularly in the Moche V artifacts from Galindo, At this cultural phase, the fine redwares characteristic of the Moche IV culture are found in association with the partially reduced blackwares which become common in the Early Chimu culture. The 53 Galindo potters were technologically capable of producing the fine redwares, however, few are included in the Galindo varieties. The Galindo potters continued the existing technological level of the Moche I - IV cultures, but with less care and attention to fine craftsmanship (Bawden 1975:17). The trend towards uncontrolled oxidation firings, and increases in the percentages of black finewares continues in the Moche Valley from Moche V through the Chimu - Inca culture (Mackey n.d. :11). The higher temperatures of the later firing practices are not clearly a technological advance but rather should be seen as a result of the shift in ceramic style. As the oxidized wares were being replaced by the reduced blackwares, the necessity to control the firing within the lower oxidation temperatures of 6oo 0 c--8oo 0 c was not required. The reduced wares are fired at higher temperatures and did not require the closer management of the oxidation firings. The Initial period collection (Gramalote) presents a peculiar problem to ceramics in the Moche Valley. The refiring test at ll50°C discloses that the earliest clay used in the valley matures at a higher temperature than that which was used during all other periods. Gramalote ceramics are more 54 refractory and the vitrification point is near the range of stoneware, or higher than cone 5 contemporary ceramics (Rhodes 1957a204). The increases in porosity noted in the second refiring test, and the lack of evidence of vitrification at this temperature range indicates that the very earliest clay used in the valley was much more fragile and underfired than the typical pottery product of the Moche Valley. In fact, the clay used in the Initial period is inappropriate to the temperature range possible in open firing. A possible explanation for the difference in the Initial period clay is the notation made by Diana Kamilli (n.d.:ms), that the percentage of feldspars present are significantly lower for the Gramalote sherds. Feldspar clay minerals include silica and alumina, along with fluxing agents which tend to lower the vitrification temperature of earthenware clays. A higher percentage of alumina in the clay increases the refractory properties of the clay, and therefore, higher temperatures are required for the clay to vitrify. Initial period sites appear to be mainly marine based settlements. During the Early Horizon, sites are located further into the interior of the valley near the river as irrigation systems develop. It is possible that the clay resource of the Initial period 55 was selected from an area of the valley close to the ocean that had deposits which were composed of clay minerals with fewer feldspar compounds but with higher alumina ratios. Later cultures oriented to the Moche River selected clays from the river beds that were less refractory and vitrified at a lower temperature. The strength of fired pottery and the capacity to achieve uniform color would make the clays desirable to the potters, and original more refractory clay deposits would not be utilized. Future geological studies of the valley may provide evidence to permit a more reliable analysis of how the clay deposits in various settlement zones of the valley differ. At the present, we can only conclude that the Initial period clays are significantly different from the clays used by all of the following cultures in the cultural sequence of inhabitation in the Moche Valley. Part III. PROBLEMS IN OPEN FIRING SITUATIONS The comparison of the quality of the Moche I - IV oxidized finewares, to the Chimu 'oxidized and reduced finewares, suggests that the ceramics of the Moche culture were fired with a greater degree of attention to the quality of the product. Generating a hypothesis to analyze the changes in behavior of the potters within the framework of the existing technologies requires that studies of the ceramics focus upon the technological achievement of the Moche I - IV potters.. The hypothesis1 Do controlled oxidation firings require closer management of fuels and are they technologically more demanding than uncontrolled oxidation or controlled reduction in open firings? In order to test this hypothesis, three areas of collecting data were utilized. 1. A discussion of the sequence of events in open firings has been included to identify problems encountered in firing ceramics. 2. Ethnographic descriptions of open firing methods in modern Peru and the results of experimental firings conducted by researchers. 56 57 r··-"----. ·-~-·-----~-----~ ! 3. Personally conducting oxidation and reduction firings in open firing situations. During the firing of pottery in open pit situations, a series of chemical reactions affect the clay minerals. In any one firing the reactions that take place are · either by chance occurrence or the result of deliberate attempts upon the part of the potter to achieve particular preconceived properties in the finished product. A number of variables exist and by means of selection of the appropriate controls the potter seeks to reach the expected results. In broad catagories the variables are found in the (1) selection of the clay resource, (2) modifications in the clay body, (3) selection of fuels, (4) placement of pottery in the pit, and (5) management of the combustion of the fuels. The complexity of ceramic technology depends upon the degree to which the potters developed controls on the forming and firing procedures to achieve a uniform product. The technology is trans mitted from one generation to the next and evolves as a cumulative cultural experience. Archaeologists have long recognized surface decoration and vessel shape as cultural indicators of time and space within independent sites, however too often the firing 58 technology is overlooked as an integral artifact trait. The management of the firing of pottery is performed within the cultural system and is an expression of traditional movements made by the potters that are as culturally significant as kinship groups or architectural styles. The body of knowledge that comprises the ceramic technology does not necessarily include the understanding of the chemical changes that occur during the firing of the pottery. Although the potters may not be capable of a scientific explanation of why the pottery is altered by their management of the firing, the validity of the technology remains in the understanding that a particular control was "correct" for a preconceived effect in the product. Hal Riegger (1972a71) describes how a Papago Indian potter in Arizona estimates firing temperature. The potter knows that when the pot is a bluish color inside it is "cooked enough" and ready to be removed from the fire. Without aparatus to measure the heat of the firing, this potter knows that the clay has reached the degree of maturity that is correct for the resources and the appropriate standards of quality. 59 FIRING ATMOSPHERES Pottery fired in open pit situations is subjected to a number of common gases that have important roles in the chemical changes that occur in the clay minerals. Water vapor, oxygen, carbon monoxide, carbon dioxide, nitrogen, sulphur dioxide, and sulphur trioxide are the major gases that are present. The first four of these gases are the most important in terms of the results that are achieved by means of th~ir presence during combustion. Each gas has a potential role in chemical reactions at different stages during the firing sequence and therefore will be discussed within a general outline of the firing sequence. The controls placed upon the combustion of fuels in firing technologies have important effects upon the resulting products. In order to achieve reliable oxidation firings, the Meche Valley potters were required to manage the combustion phases carefully. The change in firing technology that began in the Moche V culture was primarily the shift in firing atmospheres (Topic 1970:86). 1. Initial combustion In a pottery firing when fuel is ignited, carbon dioxide gas is released into the atmosphere. The chemical combination of free carbon in the fuel i • --, •'<, 0• ··--L.,_9•-"~-~V'-~ ·--~-7~k ....,._.< ..... _.,__..,_~- ...... ----·-··~- -·----~~---~---A- ,~,------~-~~-_____, !' and oxygen present in the air is responsible for the presence of carbon dioxide and the smokey appearance of the fire. The chemical reaction begins at 350oc and the reaction is very rapid at 600°C {Lawrence 1972:119). The significance of the carbon dioxide gas pertains to the manner in which the fire is maintained. If insufficient fuel is placed on the pottery setting initially, then additional fuel must be added later in order to reach the desired maximum temperature. If fuel is added to a fire that has already reached 600°C, carbon dioxide gases will be released, capable of neutralizing or preventing oxidation of iron bearing clays which results in a reduction firing. Grass fuels and branches require refueling in order to maintain required oxidation temperatures. Frequently potters recognize that refueling at slow intervals and smaller amounts of fuels at each interval results in more control over the results achieved from such firings {Shepard 1956:82). 2. Oxidation firing phase Important changes occur during the oxidation period. The potential coloring effects of the iron oxides are achieved and the carbonaceous impurities are eliminated. Well•fired reduced black wares are oxidized completely before reduction techniques are introduced. The elimination of the 61 <-'""'"""'""~-...... _...... _.~--- ' --~---·-~-.------·------·--·~· ; 'i carbonaceous impurities are important to the color effects that are achieved whether the iron clays are oxidized or reduced. The temperature range of oxidation is between 600°C and approximately 950°0, depending upon the nature of the clay resource (Lawrence 1972:119). Open firings are well within this temperature range making complete oxidation possible if technological advances in the management of the firing is present in the cultural tradition. Complete oxidation is best when the volatile matter in the fuels has burned to hot ash, permitting the oxygen necessary for chemical reactions to reach the pottery {Shepard 1956:217). Heavy ash blankets can prevent oxidation reactions which requires careful management of the fire by the potter if heavier wood fuels are extensively utilized, Time affects the oxidation reactions as well as the maximum temperatures reached, If the fire cannot be controlled so that the peak temperature is maintained, black coring may result. Setting the pottery over heavier fuels and the covering of the setting with finer fuels provides a bed of hot coals that maintains the oxidation temperature range by radiated heat below the pottery for a suffic.ient period of time to fully oxidize the wares {Shepard 1956:78). 62 The chemical reaction of oxidation that affects the iron oxides present in the clays is expressed as 4Fe0 + o ~2Fe o3, and 2Fe o + o ~3Fe o • The 2 2 3 4 2 2 3 reaction affects the ferrous form of iron oxide in the first reaction and the ferric form of iron oxide in the second. In each case, the resultant oxide is the hematite form of iron oxide that gives the fired clay the characteristic orange to purple-red color range. The lighter colors are typical of lower firing temperatures, with the same clay appearing purple at vitrification. Hematite iron oxides are refractory, indicating that when subjected to higher temperatures the color may darken but the oxide remains stable. When fully oxidized, the hematite iron oxide remains a chemically inert component in the final product, unless subjected to reduction firing conditions (Lawrence 1972:119). ). Vitrification This phase of the firing sequence rarely occurs in open firing situations due to the requirement of temperatures in excess of l000°C necessary for common red clays to vitrify. Essentially the vitrifi cation of clays is the end product of oxidation. The management of an open firing makes the temperature range of vitrification nearly impossible to attain, and not at all necessary for functional, well-fired pottery. 4. Reduction firings If conditions exist or are deliberately introduced to restrict the flow of oxygen around the pottery at oxidation temperature ranges, the oxygen molecules necessary for continuing combustion of the fuel is supplied by the hematite iron oxide. Carbon monoxide gas as a by-product gas of the combustion of fuels combines with one of the oxygen·atoms in the hematite molecule and is released as carbon dioxide gas, Fe2o3 + C0~2Fe0 + C02. The color effects caused by the reduction firing environment is the result of the transformation of red ferric oxide to black ferrous oxide. Ferrous oxide is also responsible for black coring and bloating of pottery. Bloating is the distortion of the wall of a vessel caused by trapped gases within the wall. Bloating can usually be traced to incomplete oxidation earlier in the firing at lower temperatures or overfueling which causes rapid elevation of temperatures. Excessive ferrous oxide lowers the vitrification temperature of the clay and therefore pottery can be overfired and appear bloated in the approximate temperature range of 90ooc (Lawrence 1972all9). The temperature required for successful reduction color effects is 750°C and above. Maintaining the 64 optimum reduction temperatures has a significant influence on the ability of the potter to achieve uniform results, however the temperatures in excess of 850°C 1 are usually avoided due to the action of ferrous oxide as a fluxing agent, causing overfiring at normally safe temperatures (Mayes 1962s84). R. Mac Iver (192la86) noted that glossy unglazed blackwares have been produced by cultural groups all over the world from China to Peru. Called "Bucchero", these blackwares have nearly identical color and surface quality. This indicates that the reduction firing processes that cause the changes to occur to the iron oxides in common clays were present in ceramic technologies of independent areas at various periods of time. It is apparent that reduction firing techniques are common to ceramic technologies and become alterna tives to redwares by accidental discovery or experimentation in firing processes. Reduction effects are dependent upon the ability of the potter to keep oxygen from coming in contact with the pottery when the fire reaches maximum oxidation temperatures. Fine fuels such as coarsely shredded dung are added to smother the fire or the fire is covered with dry sand or soil and these provide the necessary air-tight blanket. Air leaks cause oxidation spots on reduced wares. If the pottery is 65 r~-.."·-----~~·------~--- -~-----·~--~-"~V~-~·-~-----··-"··; ! removed from the fire too soon and is too hot upon exposure to the air, the pottery will reoxidize to red, Steps to cool the reduction fire slowly insures that the reduction grays and blacks will be maintained in the finished product (Riegger 1972a91). Bawden (1975:12) also noted that uneven color e~fects are attributed to the lack o~ proper reduction controls in the Moche V ceramics excavated at Galindo (1975:12). 5. Smudging Smudging is caused by the surface absorbtion o~ colloidial carbon which is present in reduction firings as the result of combustion of fuels without , adequate draft (Shepard 1956:216). Usually the manage ment of a reduction firing in which fuels are added to smother the fire, results in the partially burned fuels coming in contact with the pottery. Under these conditions carbon penetrates into the wares. Most reduced blackwares have been smudged as well as reduced due to the requirements of the smokey atmosphere conducive to reduction processes (Shepard 1956:88). 1 Christopher Donnan (1965:127) in his attempts to reproduce Moche blackwares common to the Viru Valley of Peru, covered the firing with fine fuels and then smothered the fire with a layer of sand. His results were successful in reducing the redwares and smudging i was achieved by means of the smokey fire. . ' c_,_, "" -<"••->•""•''-'" _____,_ __ __._,'-" .. '<'..,._'-"'-<""="'-«"<~~ ••~-··-__,._._~,_.,.,~-.-·•-"...... _•.~~··--..,...... ,..,...._,,_~,_.,~~-.....,._,,_.._.. __...... _..,,_~.-k--~----- ... --...... ,.<>~-,._.-...,. __,.,_,...,,.._,/ 66 In some cases pottery is smudged without being reduced. This is the result of limiting the draft before optimum reduction temperatures have been reached. Archaeologists can determine whether smudging or reduction has caused the black surfaces by a simple refiring test at 500°C. ,If the sherds still appear gray or black, reduction was originally achieved. The temperature range of oxidation firings (approximately 6oooc to 950°0), must be reached in order for reduced blackwares to reoxidize to redwares. Surface carbon deposits are eliminated at 500°C and will clear a sherd to redware if reduction changes in the iron oxides originally were not achieved. In the area of the physical description of pottery collections and the analysis of ceramic technologies, it is often of value to the archaeologist to be able to ascertain whether the blackwares were originally reduced (Shepard 1956: 220) • . FUELS A wide variety of fuels are used by potters to fire their products. Each fuel requires that the potter possess the understanding of the necessary management of combustion to achieve uniform predictable results. Since the quantity of fuels for a reasonably large firing is such that transportation of fuels over ·r----,..., .. ~... ,~-~------.,..,..... _ --"""'~--.._.,._,.&:~""-<~\ ! 1 large distances is impractical, and the fact that any combustible fuel can be utilized successfully, the selection of a fuel by the potter will be dependent upon the ecology of the cultural area. Different fuels vary considerably in requirements of heat retention, necessity of refueling, and placement in the fire. ,_ In terms of the reconstruction of a firing technology for a given cultural area, it is imperative that the ecology of the area must be examined for the range of possibilities in the selection of available fuels. An understanding of the combustion of various fuels assists the anthropologist in recognizing what behavior on the part of the potter can be expected in order to manage the firing to achieve his color effects and control the quality of the product. Fine fUels are comprised of grasses, reeds, straw, shredded dung, and vegetable matter such as cornstalks. Usually fine fuels are bundled to retard the rate of combustion. Fine fuels burn quickly and require replenishing in order to reach and maintain maximum temperatures. A heavy ash blanket is formed by fine fuels and may interfere with the circulation of oxygen for complete oxidation. The disadvantages of the ash blanket may be overcome by methods similar to those used by the Aymara potters of Peru. The refueling 68 of their firings takes place at slow intervals and the previous fuels are permitted to burn to a white ash indicating that nearly all the volatile matter has been eliminated, This technique also insures that the reduction gases emitted at the time of ignition of the replenishing fuels are kept to a minimum. The ash blanket may be raked away to permit air to reach the center of the firing at intervals during the firing sequence (Shepard 1956:77 & 82). Sticks and branches are classified as light fuels and have similar disadvantages as the fine fuels. Although ash blankets are not a particular problem with light fuels, replenishment of the fire in order to reach oxidation temperatures is necessary. Light fuels burn with a hot quick flame and afford maximum circula tion of oxygen throughout the firing. Dean Arnold (1975:189) noted that the Quinua potters of Peru frequently use straw or dung fuels, however the preferred fuel in this region is brush. The Quinua select the Chamizo brush that grows abundantly in the area and maintains its dry leaves on the branches. This fuel burns rapidly with a high heat potential. Dung is not universally utilized for two reasons. The moist interior climate of the Aymara region is not conducive to complete drying of the dung in preparation of its use as a fuel, and competition for the dung 69 to be used as fertilizer for field crops exists in the ecological zone. Another fine fuel found in the Moche Valley is tillandsia. Although tillandsia charcoal was the most common fuel noted in the Chimu excavations, it is inappropriate to complete oxidation firings. Tillandsia burns quickly with sooty combustion gases which would limit the oxidation period of firing and retard the free availability of oxygen (Topic 1970:e6). For this reason, we can postulate that the controlled oxidation firings of the Moche culture were not accomplished with tillandsia fuels, however tillandsia. may have been utilized in the subsequent Chimu culture. The best light fuels are dung and coal. Dung has the advantages of providing an even rise in temperature and results in a loose ash layer that is conducive to good air circulation. The combination of these two factors results in a fuel that has the potential of being managed to afford the maximum elimination of carbonaceous matter and therefore permitting the complete oxidation of iron-bearing clays, Also, the requirement of only a single layer of dung chips over the pottery to achieve successful firings-eliminates the necessity of large quantities of fuels and refuel ing of the fire. The Zuni of the American Southwest fired their pottery with branch fuels until the advent ?0 r-·-----·~·-----· -----·--•·--•-•·----~--~wm·-j ! i i ~ . ' of livestock practices in the late nineteenth century and then converted to the use of dung. The change in the selection of the fuels on their part was both the result of a significant change in their culture and dependent upon their technological experience (Shepard 1956s77). Coal has the same advantages as dung with a slow uniform rise in temperature and excellent heat retention qualities at maximum firing temperatures. The clean burning quality of coal is also a major advantage in the degree of oxidation that can be achieved with this fuel. It is difficult to access the extent to which this fuel was used by prehistoric potters as data on pottery firing fuels is scarce. Anna Shepard (1956:77) identifies the Pueblo Indians as a cultural group that used coal in prehistoric times as a fuel, but no other sources of data on the use of coal have been located at this time. The use of coal prolongs the firing sequence far more than any other fuel. Since / duration of firing is important to the oxidation of pottery, a fuel that retains heat longer has advantages for the potter. Dung reaches maximum temperatures in approximately forty-five minutes and the temperature falls to 500°C within the next ten minutes, according to firing experiments conducted by Anna Shepard. Coal 71 firings reached maximum temperatures in three bours and took another three hours for the fire to cool to 500°C (Shepard 1956:77). A final fuel to be considered available for potters, but inappropriate for the Moche Valley, is wood. Heavy fuels are not extensively available in desert regions and are not preferred by potters when lighter fuels are locally present. The main disadvantage to wood is that the fuel can cause damage to the fragile unfired pottery when placed on the firing. Also, the combustion of wood results in heavy concentrations of soot and residue. The placement of pottery and fuel in a wood firing requires that a buffer of clay sherds or metal sheets must be devised to protect the pottery from damage during firing (Belknap 1964:204). FUEL IN THE MOCHE VALLEY In the Moche Valley, fine and light fuels were available to the potters. In comparing the available fuels, grasses, reeds, branches, and dung, the latter fuel affords the optimum oxidation conditions (Shepard 1956:77). In terms of the Moche firing technology, the ideal fuel for perfect oxidation results is llama dung. Llamas were domesticated beasts of burden in the Early Moche culture, and probably domesticated much earlier (Mackey n.d.:27). 72 ------·------~------··------1 At the Moche V site of Galindo, a llama compound has been located adjoining a pottery workshop. Speculation has been made that the llamas were used to transport clay to this workshop, however the presence of the pens also indicates that dung fuels were immediately available (Mackey n.d.:23). During the Moche culture, agriculture is fully developed and a stratified society is evidenced by high status burials. The finest ceramics were abundant as grave goods such as the tomb of the warrior god, excavated by W.D. Strong (1947); and the burials excavated by the Chan Chan - Moche Valley Project (Donnan and Mackey n.d.:l8). As craft objects of status, it is possible to hypothesize that the premium placed upon the pottery would have required that the potters had access to the ideal fuel resources in order to produce the desired products. In light of the quality and characteristics of the pottery, and the nature of social structure in the Early Intermediate period, it is very probable that the potters utilized dung as firing fuel from the Salinar to the Moche cultures. 73 r--~.. --·-·---~------~-~-·---·--·-·--~-~ { I ' PROCEDURES FOR OPEN FIRINGS 1. The first step in the preparation for an open firing is to locate a site on level ground or small rise that will permit good draft. A depression is made in the soil four or five inches deep and a bank of soil or rocks are arranged around the depression to assist in the retention of heat. 2. The pottery to be fired must be dry. Although the pottery seems to be completely free of all moisture, a percentage of moisture is nearly always held by capillary action and must be eliminated before firing. If the pottery is placed in a firing situation and moisture is present, the pottery may explode due to the sudden escape of steam from the clay. Two methods of preheating pottery to eliminate moisture are common. The pots may be placed on a layer of smoldering dung and rotated periodically to insure that they have dried completely, or a preliminary fire may be started in the firing pit and the pots placed on the edge of ; the pit close to the heat and rotated frequently to preheat them and cause the water to be expelled as steam. A preliminary fire also serves the function of preheating the pit and drying the soil as well as providing a bed of hot coals on which to place the pottery and fuels. In a very arid area the elimination 74 F''"---~-~------,---' I I of water by air drying may have been sufficient to make I' the preliminary preheating step unnecessary. The Mocha Valley potters probably did not find it necessary to preheat their pottery as evaporation of water from the surface of the drying clay was probably rapid due to the lack of humidity (Collier 1967:269). ). In order for air to be capable of surrounding the oxidizing pottery, the pottery setting must be slightly elevated, Some potters place stones on the ground to support the pots, but the far more common method of placing a bed of light fuels over the coals is equally reliable. Placement of the pottery depends primarily on the number of pots to be fired. A large collection of pots is placed with heavier pieces on the bottom upright, and bowls inverted and placed in alternating rows supported by the larger pot lips. If only a few pieces are to be fired, they are placed in a single layer, however for stability, the bowls are usually fired in an inverted position (Riegger 1972:66). 4. A layer of large sherds may be placed over the wares to prevent contact with the fuels. If the potter is capable of achieving optimum oxidation conditions, this precaution can be eliminated. A long firing period at maximum temperatures restricts the effects of smudging and reduction when available oxygen is present. A large pottery setting of more 75 than 10 vessels, retains heat for long periods of time and along with optimum conditions makes sherd protective layers WL~ecessary (Shepard 1956z76). The characteristics of the Moche I - IV oxidized redwares indicate that the potters of this culture were well aware of precise controls necessary for complete oxidation. In the light of their technology, it seems appropriate to assume that protective sherd baffles were not utilized in their firings. Sufficient attention to temperature control and fuel selection are the main variables conducive to complete oxidation and in my opinion, were included in the Moche technology. 5. Fuels are placed on the top of the firing setting and ignited by means of the hot coal layer of the preliminary fire. When the temperature of the firing exceeds 6oo°C, additional fuels must be added with extreme caution to avoid reduction gases in the firing atmosphere. Maximum temperatures are achieved in approximately thirty minutes as long as the fire continues to burn. 6. Removing the pottery from the fire occurs at various stages of the firing sequence depending upon the area. Some potters remove pottery as soon as the maximum temperatures have been achieved, while others 76 '---=-') r--·------·-··------·------. ~ 1 \ i l may wait until the temperature falls to 700°C or lower before ashes are raked away and the pottery is removed and cooled (Collier 1967&269). Safe temperatures for removing pottery depend primarily on the nature of the clay and the maximum temperatures that were achieved. Some clays with high percentages of tempering materials, and consequently a more open clay body, are more resistant to sudden changes in temperature and can be removed from the fire sooner than a denser clay body. Slightly underfiring pottery at temperatures of 700°C to 800°C rather than the maximum heat potential of 900°C to 950°C, by using a smaller quantity of fuel, also affects the ability of the pottery to survive removal from the fire without breakage (Shepard 1956:90). 7. When reduction and smudging procedures are desired by the potter, additional management of the firing is required; however, the sequence remains the same as that used to achieve oxidation until the maximum firing temperature is reached. When the firing peak has been achieved, additional fuels are usually added. A fine fuel works best for reduction since the availability of oxygen can be limited by covering the entire firing with the fuel. The ignition of the fuel provides the reduction environment and the limitation of the draft provides the optimum 77 ,------conditions for the chemical changes in the iron oxides. Fuels in contact with the pottery account for the fact that nearly all reduced pottery is smudged in open firings. The temperatures that are achieved and the length of time that they are maintained affect the ; degree of reduction that occurs. Often the firing is covered with earth or sand to retain the heat and insure that the draft is completely eliminated. If a sherd layer was placed over the wares during the placement of the pottery, it is removed after additional fuels have been added and they have ignited. The potter pushes the fuel close to the pottery to achieve the deep black colors of smudged pottery. Pueblo potters remove their blackwares from the fire at 4oooc to 570°C assuring that the reduction effects will be permanent. Reduction effects take from fifteen minutes to one hour; the removal of pottery by the Pueblo potters occurs after the time interval that they believe to be correct, has passed (Shepard 1956188). Removing reduced pottery from the fire above 600°C may result in the reoxidation of the pottery to redwares. VARIATIONS IN FIRING PROCEDURES General procedures for open firings are similar in various cultures all over the world. Methods of preparing the ground, placement of the pottery, fuels, 78 ~------~ ! and management of the fire display a basic pattern ; with variations peculiar to specific cultural traditions. Descriptions of procedures used by modern Peruvian potters and laboratory researchers studying open firing methods has been included here as a preliminary , step to planning firing experiments. An overview of the basic necessities of open firings is provided by Donald Collier's ethnographic study of the potters of the north coast of Peru. We cannot be c~rtain that the techniques utilized in the far north coastal valley of Lambayeque were similar to those of the potters of the Moche Valley. Collier's description of. the Lambayeque procedures at best will provide a possible framework of procedures that the Moche Valley potters utilized in their firings. The pottery was preheated on smoldering dung to remove all traces of moisture prior to placement in the firing pit. The vessels were rotated constantly for 2 - 3 hours. The firing pit measured 2 x 3 meters and was 25 centimeters deep~ A bed of finely broken sticks and branches placed in the bottom of the pit supports the pottery and provides bottom heat for even distribution of heat upon firing. A -hundred and twenty vessels were placed in the pit in alternating rows with larger vessels supporting a 79 i.. ·-·~--· - ~··-· ------·-·-~-·-~-~.,; !i second layer of smaller vessels on their rims. A layer j ' of large potsherds covered the pottery and acted as a buffer to retain heat and prevent fuels from contacting the pottery. A layer of sticks was placed over the sherd covering and ignited. A final layer of dung was placed over the entire setting immediately after the wood fuel ignited. The firing was allowed to cool overnight before vessels are removed from the setting (Collier 1967r269). Christopher Donnan (1965:127) followed these general procedures in an effort to duplicate the Moche culture oxidized redwares. Early attempts resulted in fire-clouding but later firings produced good oxidation results. Donnan also experimented with reduction firings by adding additional fuels at the maximum temperatures and immediately covering the setting with sand to block the draft and produce' reduction conditions. Some pieces in Donnan's experiments were overfired probably due to the failure to estimate the proper amount of fuel necessary. Dean Arnold's (1975:202) study of pottery making in the Ayachucho Basin in Peru noted that environmental factors may be the cause of variations in firing procedures. Elaborate drying systems for ' pottery and fuels evolve when they are necessary due 80 r -··-, j to humidity problems in some areas. Wet fuels lower firing temperatures, cause uneven heating, and breakage caused by steam in the firing sequence. Humidity problems in Ayachucho are limiting factors for the potters of that area and prevent them from pottery making activity on a year-round basis. The Aymara potters of southern Peru and Bolivia prepare a small circular depression in the earth and circle the pit with stones to retain the heat. No preliminary heating of the pottery occurs. Vessels are placed on a layer of dung and covered with bundles of grass and dung. After the fire has burned to eliminate i. most of the volatile matter in the fuels, holes are poked in the fuel layer to increase the draft. Pottery is removed from the setting after two hours while the vessels are still hot. No temperature recordings were taken by Harry Tschopik during the Aymara firings, however the peak temperatures had been reached and the setting was losing heat at the time vessels were removed from the fire. Good oxidized reds were achieved without a layer of sherds to eliminate smudging due to the length of time achieved in the firing. Fire clouding and smudging are eliminated under prolonged oxidation conditions. A final finish was achieved by 81 ------·-·--··--··~------·-·-- polishing with a greasy cloth for additional luster (Tschopik 19501215). NOTES ON EXPERIMENTAL FIRING In order to assess the degree of difficulty encountered by the potters of the Moche Valley, four firing experiments were conducted at Northridge, California. Two firing tests were accomplished in the month of April, and the remaining two tests in May of 1976. Four vessels were fired in each experimental firing and were constructed utilizing a comparative local earthware clay. Construction methods for the vessels are found in the work of Christopher Donnan {1965), in which experimental construction and firings were performed to analyze the technology of the arti facts excavated by Max Uhle at site F, in the Moche Valley. Sixteen vessels were constructed utilizing Donnan's methods which resulted in adequate reconstruc tions of vessels typical of the Moche and Chimu cultures. The major objectives of the firing experiments were 1) to assess the degree of difficulty in achieving optimum oxidation, and 2) to compare the technological processes of oxidation and reduction firings for ease of execution. These objectives as stated in the original hypotheses werez Do controlled oxidation firings require closer management of fuels and are they technologically more demanding than uncontrolled 82 ,~---·~--~------'------~; oxidation or controlled reduction in open firings? (see page 14). Two distinct firing methods, involving different procedural controls, were utilized in order to theoretically reconstruct firing technologies appropriate to the technological systems inherent in the Moche and Chimu cultures. Preliminary preparations for firing experiments require a minimum of technical equipment. In order to measure the exact temperatures achieved during the firing process, a pyrometer and thermocouple are necessary. Precise measurements were achieved with thermocouples of chrome-alumel wire with silica-glass : sheathing to protect the wire from exposure to the fire. Heat-proof shields for the pyrometer were devised from fire-brick or transite panels to protect the instrument from radiated heat. The pyrometer used in the firing experiments in this study is capable of measuring heat from 0°C to 1300°C. A firing site was selected on level ground at least fifteen feet distant from obstructions which could interfere with proper draft. An area measuring thirty feet by thirty feet of unimproved land was found to be adequate for small firings. A depression was prepared of approximately twelve centimeters depth and a diameter of one meter. A bank of earth prepared from the soil removed from the depression helped to 8J retatn the heat during firing~an(f'to"make·-· soif'''-~~~----,-~" ...... ,.... available for covering the setting when reduction fir ings were accomplished. Two basic types of fuels were used in the firing experiments for purposes of comparison. Light fuels consisting of shrub-oak twigs and branches were utilized as fuel in the first two firings, (generic name& Quercus Dumosa, commonly called Chapparal). Shrub-oak was selected for two reasons, 1) it is a native desert shrub with small leaf area, and 2) it is similar in physical properties to the tillandsia shrub which Topic (1970:86) speculated was used as fuel in the Chimu culture. Shrub-oak and tillandsia are twiggy shrubs which burn with high heat caused by free oxygen easily penetrating the stacked fuels. Dried cow dung chips were selected as fuel for the final two experiments based upon the hypothesis that dung fuels were used in the Moche culture. Fuel quantities were stored near the pit for easy access when needed. To begin the firing sequence, a fire was built in the pit with branch fuels. The pottery to be fired was preheated on the perimeter of the pit to insure that the pottery was free of all moisture prior to firing. Rotating the pottery at regular intervals was necessary to evenly preheat the vessels. < i When the preliminary fire had died down to a bed t l , of coals, a layer of branch fuel was placed in the pit L----~-----· J 84 to support the pottery and to provide bottom heat during firing. It was necessary to work rapidly in placing the pottery on the bed of fuel as the interval before ignition is approximately five minutes. Various systems of supporting the pottery and elevating the pottery to permit maximum available oxygen during the oxidation firing period have been developed by potters, however fuels proved to be sufficient in experimental firings. At this point in the firing sequence, variations in firing procedure. were imposed to provide comparative data on the results. Following are descriptions of the four experimental firings. FIRING #1 - OXIDATION (USING BRANCH FUEL) 4 VESSELS Four vessels were placed on the fuel bed in the pit. One large vessel was surrounded by a protective layer of large sherds to compare the fired color results with the remaining vessels exposed to the fuels. The entire setting was covered with light fuels of twigs and branches. Figure 9 labeled "BRANCH FUEL FIRINGS" on the following page contains a record of time and temperature for the firing. A gentle wind caused some problems of controlling the fire making a wind screen constructed of eardboard measuring 4'·x 8' necessary to equalize the draft. 900 ---- Oxidation Firing /11 -----Reduction Firing #2 800 minimum ~ oxidation point 700 I'\ , I \ I \ 600 I \ I I I I .500 I I \ I \ \ 400 \ \ \ \ 300 ' ' ' I ' ...______I ' ' 200 I / 100 0 0 10 20 40 so 60 Tilt.E IN MINUTES Figure 9. Branch Fuel Firing. I I ------~ 86 900 Oxidation Firing #3 800 minimum ~ oxidation point 700 600 soo 400 ~ 300 ~ 0 H f-tz f'l 0 t/) 200 ~ t1 0 ~ t1 100 ~ < re~ "'tl 0 0 10 20 30 40 50 60 TIME IN MINU'l'ES Figure 10. Cow Dung·Fuel Firing, Firing with branches as fuel required refueling to maintain a constant rise in temperature. A quantity equal to one-half of the original fuel load was added to the firing when the consumed fuels had fallen away as ash and the temperature was still below 800°C. Refueling was accomplished in small amounts at several intervals to minimalize reduction gases. A maximum temperature of 800°C was reached in thirty-five minutes and a sharp decline to 4oo0 c occurred in an additional twenty-five minutes. The pottery was removed from the firing at 400°C and allowed to cool at the edge of the firing pit. Well fired pottery resulted from this firing with some fire clouding on all pieces. The vessel, which had been protected with the sherd layer, was identical to the vessels that were exposed to the fuels. Apparently in this experiment fire-clouding was caused by the reduction gases emitted at the refueling or by the short oxidation period. One open vessel developed a vertical crack while firing. It was noted that this vessel was warped from drying and showed signs of stress before firing. The color of the paste of the fired vessels were comparable to the range of color expressed in the Moche I - IV variety Ml5 (Munsell Color Chart designated, 88 r--- l 5 YR 4/4, reddish brown). The core of the vessels walls were slightly darker, typical of the Meche V variety 6 DE (Munsell Color Chart designated, 5 YR 5/4, reddish brown). FIRING #2 - REDUCTION (USING BRANCH FUEL) 4 VESSELS Preparation for the second firing experiment was identical to the first firing up to the point that maximum temperatures were reached. An increase in the wind made controlling the second firing difficult and only 750°C was achieved with continuous refueling. As it was difficult to maintain peak temperatures, steps were taken to provide reduction conditions when the temperature dropped to 600°C. Fine shredded commercial manure was used to smother the firing and provide reduction gases. An immediate drop in temperature to 450°C was recorded and the entire firing covered with soil to maintain heat as long as possible. Several problems were associated with this experiment and the results were generally unacceptable. The pottery was removed from the firing at 250°C, and showed evidence of smudging, Upon close inspection of the core of a vessel wall, the vessel showed signs of incomplete oxidation and no evidence of reduction. 89 In analyzing the results of this experiment, several factors were responsbile for the results. 1. The peak temperature was too low due to problems associated with the wind and oxidation was therefore incomplete. 2. The time interval at the maximum temperature was too short for the clay to oxidize successfully. 3. Reduction was not achieved due to fuels added at temperatures too low for chemical changes to occur. Reduction requires an excess of 750°C at the time additional fuels are added and the draft is eliminated. An even smudged black surface was achieved indicating that even under adverse conditions smudging is easy to accomplish. The color of the paste was identical for all vessels. The surfaces of the vessels were comparable to the Chimu variety CC 1 (Munsell Color Chart designated 2.5 YR 3/0, very dark gray). The core of the vessels walls were comparable to the Chimu - Inca variety CI A (Munsell Color Chart designated, 2.5 YR 6/8, light red). FIRING #3 - OXIDATION (USING COW DUNG FUEL) 4 VESSELS The main objectives in this experiment were to provide comparative data on the effects of the use of dung fuels over branch fuels, and to assess the value of 90 elevating the vessels in the ·firing pit to improve the draft. Four vessels were placed on an improvised grate which was positioned over a bed of branch fuels in the pit. A bed of coals resulting from a preliminary heating fire in the bottom of the firing pit ignited the fuel under the vessels in three minutes. As the fuel began to flame, a layer of cow dung slabs was placed around the vessels on the grate and permitted to come in contact with the vessels. Ignition of the dung occurred within another two minutes and provided a steady rise in temperature well into the oxidation temperature range. Maximum oxidation conditions were reached in twenty-five minutes and were maintained for twenty minutes without refueling. The color of the vessels surfaces were comparable to the Gallinazo variety G8 (Munsell Color Chart designated, 2.5 YR 4/6, red). The cores were comparable to the vessel surfaces and did not show a variation in color. One vessel important for its analytical implications, resulted from this firing (see Figure 15 page 98 and Fig- . ure 14A page 97). This vessel had been oxidized completely from the middle of the body to the base, and was partially oxidized from the shoulder to the spout. The elevation of the vessels in the firing permitted maximum draft 91 r----~------~-.1 j eondi tions around the vessels, however it is obvious I that the upper portion of the vessel was too far from the source of the heat and was prevented from being oxidized. This vessel demonstrates the importance of heat and draft in open firings. Excess draft cooled the upper portion of this vessel while the lower half of the vessel, subjected to more heat, was in optimum oxidation conditions. Apparently, the elevation of vessels involves risks to the potter in open firing situations and demands a precise control over the placement of the vessels and fuels to insure even heating and draft. A second observation concerning this vessel concerns the dark surface at the spout of the vessel. Optimum oxidation conditions eliminates soot deposits on vessels due to contact with fuels and reduction gases in the early stages of firing. As the clay oxidizes above 750°C, the. soot is burned off and clear colors result. Although the entire vessel was surrounded with fuel, only the bottom half of the .l' vessel was subjected to sufficient heat and draft to burn off the soot and eliminate carbonaceous matter in the clay. 92 ·--·· ---·------·-·- --~------·------~ FIRING H4 - REDUCTION (USING COW DUNG FUEL) 4 VESSELS A final reduction firing was accomplished in which higher oxidation temperatures than firing #2 were achieved. Steps to reduce the firing environment were introduced earlier in the firing sequence at higher temperatures. The firing was smothered with shredded commercial manure at the maximum temperature of 800°C and the firing was not covered with soil as it was in the reduction experiment #2. The vessels were removed from the firing at approximately 450°C and the vessels were fully reduced. The vessel surfaces were comparable to the Early Chimu variety EC 14 (Munsell Color Chart designated, 10 YR 4/1, dark gray). The core of the vessels walls were comparable to the Chimu variety CC 1 (Munsell Color Chart designated, 10 YR 5/1, gray). ... ····--·-··---., I EFFECTS FIRING METHOD FUEL MAX. TEMP oc SURFACE CORE I #1 oxidation branch Boo 5 YR 4/4 5 YR 5/4 reddish brown reddish brown #2 reduction branch 750 2.5 YR 3/0 2.5 YR 6/B very dark gray light red #3 oxidation cow dung B50 2.5 YR 4/6 2.5 YR 4/6 red red #4 reduction cow dung Boo 10 YR 4/1 10 YR 5/l I dark gray gray I .l Figure 11, Comparative experimental firings. .... ··- ·-.. ····-···· JI '.{) \...) 94 ------·- The hypothesis that uniform results are more dif- ficult to achieve in oxidation firings as opposed to reduction firings was verified in the experimental firings. In firing experiment #1, the vessels showed incomplete oxidation effects on vessel surfaces and in the sherd cores. Firing #2, although considered to be an unsuccessful attempt at reduction firing, resulted in uniform vessel surface color as a result of smudging. The second attempt at achieving a reduction firing (firing #4), was significant in that reduction effects were relatively easily accomplished. Firing fuels were controlled to produce higher temperatures than the maximum achieved in the earlier reduction firing (firing #2). Firing #3, in which controlled oxidation objectives were realized, required more attention to firing details of fueling, and management of the firing atmosphere. The color achieved with cow dung fuels were more uniform and brighter than branch fuels. Slips fired to a cleaner white and showed light gray in all other firings. The degree of oxidation was more complete in firing #3 indicating that dung is a superior fuel as Anna Shepard suggests (1956a77). 95 Figure 12a. Pottery of Firing #1; note layer of sherds over one vessel. Bed of fuel is visable under pottery. Figure 12b. Firing #1 with layer of branch fuel in place. 96 i"",_,.-~,.,-;o-="'"'"""'-·-~=-,_._,,•.==.-;:Q."'...,.~-...... ,.>='~'"""-"""'"4"~.-~· ~~~···0>··----·-"---~-----~ ..... ~-·b>Y-""''"<"<'=·~~-~.... ;o>•.-.:;..JttJ'o">{ I . i ' I ~ ' ·Figure lJa. Firing #1 at completion; note layer of hot ash present at bottom of the pit. Figure 13b. Oxidized vessel from Firing #1. 97 Figure 14a. Firing #3. Vessels are elevated on a grate for improved draft. ------~-~---~---- ·~~-"--.-.~.-,-- Figure 14b. Firing #3. A layer of cow dung fuels covering the vessels shown in Figure 14a. 98 r,- .. -- .. "~----·--~.. ·,·--~-~,~~·-,-~·~----~------~~---~~~---~-----~---~-~~,-~---~~ ' . . L~------Figure 15. Dark spout is evidence of incomplete oxidation. The chamber of the vessel was well-oxidized. Firing lf3 Part IV. SUMMARY OF CONCLUSIONS OF THE PROJECT Color analysis of the Chan Chan - Moche Valley Project ceramic site collections indicates that there 1 are only four typological catagories based upon vessel colorz 1) matte red, 2) shiny dark red, 3) matte black, and 4) shiny black. The shiny darker colors in both redware and blackware are caused by burnished surface treatments before firing. Deviations from these four catagories, noted in the site collec tions, were unintentional on the part of the Moche Valley potters. The data provided by Diana Kamilli (n.d.ams) on the nature of the pastes, and the refiring test conducted on a representative sample selected from the , site collections, has shown that the clay used in the valley is uniform from the Cupisnique to the Colonial cultures. Color variations, therefore, are to be viewed as the result of the control (or lack of control) in the firing atmosphere. When subjected to ideal oxidizing conditions in the refiring test, uniform color results were achieved. Comparisons between oxidation and reduction firing results indicate that complete oxidation of carbonaceous clay is the most difficult objective of ,.,~--~ "~-~-·~·""· --···~~q·"-....-~~--- __ ...,.._~~----~-··'"'·~_..__,._____._ ...... ,.,._.._.._ __.,..,.._...... _,.,...... ,. __ _... __.,._ ___ .... ______...... ~-.u-.-.... -- .. I 99 100 r·------~-~------·- 1 open firings. Reduction firings are easier to accomplish if uniform color is a major criterion of the degree of success achieved. When clays are intentionally smudged by reduction procedures, the chances of color variations are minimalized. As discussed in the Introduction, the sequence noted by Bennyhoff in the Viru Valley, from incomplete oxidation to complete oxidation in the Salinar, Gallinazo, and Moche cultures, is to be viewed as the trend of a developing technology. The Salinar culture is preceded by the Cupisnique culture in the Moche and Viru Valleys. Cupisnique finewares are characteristically smudged, reduced blackwares and incompletely oxidized redwares. It is not surprising that the general sequence of firings in the Moche Valley for finewares is initiated by blackwares, followed by incomplete oxidized wares, and reaches maximum perfection in the Moche culture with fully oxidized redwares. In terms of what is possible with limited technologies, blackwares can be expected to precede fully oxidized redwares. As the technology develops and the controls are instituted to produce uniform redwares and clear slipped designs, more difficult firing effects are possible. 101 The Moche I - IV potters were firing at optimum oxidation temperatures for the local clay resource. Comparative porosity measurements have shown that the ceramics beginning in the Moche V culture are fired at higher temperatures and with less attention to optimum oxidation. The higher firing temperatures are not a technological advance. Maximum oxidation temperatures range from 6oo0 c to 800°C. As the demand for well-oxidized redwares decline, carefully controlling the firing temperatures becomes unnecessary. The shift in firing technology occurring between the Moche and Chimu cultures is an important change. The Galindo site is significant because the ceramics are transitional between the fully oxidized redwares of Moche I - IV and the reduced blackwares and uncontrolled oxidized redwares of the Chimu (Bawden 1975:17). Bawden (1975:18) also notes that the potters of Galindo were capable of producing oxidized red finewares of high quality; however, they also produced oxidized ceramics of lower technological quality. The general trend towards uncontrolled oxidation and the increased frequency of reduced blackwares begins in the Moche V culture and continues into the Chimu. 102 Evidence indicates that the decline in the quality ' · of Chimu ceramics was not due to a decline in the level o:f technology. Therefore, the question arises as ·to why the change occurred. Since the rich, high-status burials of the Moche culture were indications of a highly developed social class system, then the high quality grave goods were symbols of rank and prestige (Donnan and Mackey ms:l8). At Chan Chan the social distance between the classes was certainly large. The complexity of the urban center of Chan Chan and the extent of the empire in the northern portion of Peru which they controlled is conclusive evidence that positions of wealth and prestige were even greater for the Chimu rulers than they were in the Moche culture {Moseley 1975z219). Excavations at the Chimu urban center of Chan Chan have indicated that a large segment of the urban population was engaged in cottage-craft industries. The noble class was apparently in charge of the management of the quality and quantity of the products, and in direct control of the redistribution of goods (Moseley 1975:221). Topic (1975:51) has found evidence for craft production workshops in Chan Chan; with metalworking and weaving workshops to be common industrial activities. I lOJ r-·---·-'"""·~·~-~---·-~~·-·~---~---~---~-~·~ .. -~_.o=·····~~~·--~···,.-·~--~~~·"~-···~,~-·==··· l ~ I Stone, shell, and woodworking sites were also identified (Topic 1975:37). Recent evidence concerning the craft specialization activities at Chan Chan indicate that the urban population was involved in the active manufacturing of goods for exchange. High-quality weaving products and metalworking was probably produced i solely as symbols of rank and status for the ruling aristocracy (Moseley 1975:223). It is important to note that no pottery workshops were found by Topic in Chan Chan. We are certain that local production of ceramics did occur at the Chimu capitol, however the frequency of weaving and metal- . working workshops suggests that these products were in higher demand by the aristocracy. The failure of Topic to discover a pottery production site may have several possible explanations: 1) the pottery craft locations may have been some distance from Chan Chan, closer to the site of major clay resources; 2) pottery manufacturing may have been restricted to a confined area of urban Chan Chan, that was not included in Topic's sample, and 3) it is also possible that pottery was manufactured by the rural population engaged in agricultural activities and not a product of Chan Chan urban craftsmen. 104 The evidence indicates that Chimu technology was capable of producing ceramics of the quality of the previous Moche cultures. The decline in the quality of the Chimu ceramics in my opinion, is an indication of a change in the symbols of rank and status. At Chan Chan, the importance of high status burial pottery apparently was replaced by metal products and fine textiles. The conclusions indicated by Topic (1976) on the frequency of the metalworking and weaving locations in Chan Chan are consistent with the evidence presented here. The previously mentioned conclusion that uncontrolled oxidation and controlled reduction firings are easier to accomplish· than the controlled oxidation firings of the Meche cultures, is consistent with the evidence from Chan Chan. Mass production techniques of mold-made pottery were common at Chan Chan during the Middle and Late Chimu phases (Donnan and Mackey ms:40). With a decline in the demand for ceramics as symbols of high status, the standards of quality typical of the Moche ceramics were no longer required. The ceramic technology of the Chimu culture is a continuation of the Moche technology with ~n emphasis upon mass pr~duction. From this data, we can postulate 105 r---··~---~~~-~-"·•-=w•~~~--~--~"•=-=~·-·~-·~-~-~~"--••--~-.~--•--•~-•-«,.- •-c ~-''-"~·.....,><"-- . ...--·~:...=«v.·...-,,~=-.,.- """""'~~.:.t...~.._...... ,,,.._.,.,.,.,.,._,_._-""~=~-"'--- 1 that complete oxidation firings were not required in ! the Chimu ceramic industry, however, the fully developed technolo~r to produce ceramics typical of Moche I - IV redwares is present. Therefore, the Chimu ceramics indicate a shift in style rather than a decline in ceramic technology. _,l - -·------~------~--- ~------~ BIBLIOGRAPHY l :Peruvian studies; general background BAWDEN, GARTH 1975 Galindo: A study in cultural transition. Unpublished manuscript for the school of American Research, Advanced Seminar, "The desert city and its hinterland," Santa Fe, New Mexico. BUSHNELL, G.H.S. 1957 Peru, Praeger. DONNAN, CHRISTOPHER and CAROL J. MACKEY n.d. The burials from the Moche Valley • . Unpublished manuscript. 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(ed.), Scientific methods in Medieval archaeology, (389-408). University of California Press. SAYRE, E.V., A. MURRENHOFF, and C.F. WEICK 1958 The non-destructive analysis of ancient potsherds through neutron activation. Brookhaven National Laboratory, BNL 508 (T-1222). WEYMOUTH, J.W. 1973 x-ray diffraction of prehistoric pottery. American Anthropologist 38 (3):339-344. . ! --· ...... -. ". CHART l COLOR FIRING TEST ORIGINAL COI.OR REFIRED TO 90000 varie.ty inner outor core inner outor core Grama1ote ' InLtiul period GR lA 5 YR 3/'J 7 • .5 YR. 3/2 5 YR )/3 2 • .5 YR S/8 2 • .5 YR .5/6 2.5 YR S/6 dk reddif::h brown dk brown dk. rt~ddiah brown red red red GR 3 10 YR 4/1 10 YR 4/1 lO YR ~/1 2,5 YR 5/8 2,5 YR 5/3 2,.5 YR .5/8 dk gray dk gray ffr"'Y red · red red 1-' 1-' CA l 10 YR 5/2 2 • .5 m 4/6 .5 YR 2/1 2 • .5 YR 5/8 2,5 YR .5/8 2.5 YR 5/8 -t:" grayish brown red black . red red red Caballo Muerto Cup1sn1quo 2 lO YR 4/1 10 YR 4/2 · !.0 YR 5/1 2 • .5 YR .5/8 2.5 YR 5/8 2,.5 YR .5/8 r.l.k gray . elk grc:.yish brown gray rad red . red 8 2,5 YR 4/6 10 YR 4/1 lO YR 3/1 2.5 YR .5/8 2 • .5 YR .5/8 2,5 YR .5/8 I'tHl d.k gray vory dk gray red red red 18 .5 YR 4/4 10 YR 4/6 5 YR .5/4 2 • .5 YR 5/8 2,5 YR 4/6 2.5 YR .5/8. reddish brown rau reddiah brown red red red Cerro A.rena Sallnar s 34 7.5 YR .5/2 10 YR :3/1 5 YR 2/l 2,$ YR 6/8 2 • .5 YR 4/8 2,.5 YR 6/8 'bro'fi.'Tl vary dk ;z;ray b1aclt 1t red red lt rod s :n 7,.5 YR )/0 10 YR 6/l 10 YR 6/l 7 • .5 YR 7/4 7 • .5 YR 7/4 7,5 YR 7/4 very dk grq l·t. {!,lay lt gray pink pink pink SG 24 10 R 4/8 10 R 4/8 2 • .5 YR 2/0 2,.5 YR .5/8 2 • .5 YR .5/8 2,.5 YR .5/8 rad red 'black re'l red . r!!cl (Continued on following page) CHART 1, Continued ORIGINAL COLOR REFIRED TO 9000C ' yariety inn(lr outer core inner outer. core Ce.rro Orejas I Gallinazo G B -~.5 YR 5/6 2,5 YR 4/6 2,5 YR 5/6 2,5 YR 5/6 2.5 YR 5/6 2,5 YR 6/8 ted· red rod red red lt red G l6/l6A. .2,5 YR 5/4 2,.$ YR 5/6 2.5 YR Sfl• 2,,5 YR 6/8 2 • .$ YR 5/8 2.~ YR 6/8 reddish "brnwn ra'l reddish brown lt rad red lt rod .. G 24 ·5 YR 6/6 10 R 4/8 5 YR 2/l 2.5 YR 6/8 2.5 YR 4/6 2,5 YR 6/8 .reddi9h yellow red black lt red red lt rod Pyramid Site Mocha M 15 5 YR 4/4 5 YR 4/4 5 YR 4/4 2.5 YR 5/6 2,5 YR 5/6 2,5 YR 5/6 t·eddish brown reddish brown redC.lsh brcwn . red red rei:l "M 19 10 rt 5/6 10 YR ?/4 lO R S/6 2.5 YR 6/6 10 YR 8/4 ' 2,5 YR 6/6 J.+ed SLIP red lt red SLIP lt red M 20 :to YR 4/l 10 YR 4/l .S YR 4/l 5 YR 7/6 5 YR 7/6 . 5 YR 7/8 dk gray dk gray dk gray reddish yellow reddich yellow reddish yellow · Galindo Mocha V 3A DE 2.5 YR 5/6 5 't'R 5/4 2,5 YR 5/6 2,5 YR 5/8 2,5 YR 5/6 2,5 YR 5/8 red reddi':lh brown red red red red 6 DE 2, 5 YR .S/!~ . 10 YR 4/2 2,5 YR 5/4 2,5 YR 5/8 2 • .$ YR 4/6 2,,5 YR 5/8 reddish brown dk g~ayish brown reddish brown red r~d red .. 8 DE .10 YR 5/l lO YR 6/4 Both innar and 2.5 YR 5/8 2,,5 YR .5/8 2,'5 YR 5/8 gray lt yellowish bro'N.n ou·ter divided, red red red (Continued on following page) 1-' 1-l \..1\ CHART 1, Continued ORIGINAL COLOR REFIRED TO 9000C variety . inner outer core I inner outer core (Not Chan Chan) Early Chimu EC 8 ' 2,5 YR 5/4 10 R 4/6 2,5 YR 5/4 2 • .5 YR 5/8 2,.5 YR 4/6 2,.5 YR 5/8 reddieh brown . red reddish brown red red red EC 10 · 7,5 YR .5/2 7,5 YR 4/2 10 YR 5/l 2,5 YR 5/6. 2 • .5 YR 5/6. 2.5 YR 6/8 "brown brown gray red red red EC 14 10 YR Vl 10 YR 6/l 10 YR 6/l 2,5 YR .5/8 2.5 YR .5/6 Z.S YR .5/8 dk gray gray gray red red red Chan Chan Chimu cc 1 10 YR .5/l 2,.5 YR )/0 10 YR .5/l 2.5 YR 6/8 2,5 YR 6/8 2 • .5 YR 6/8 gray very dk gray gray lt red .. lt red lt red cc 2 s y 5/l 2 • .5 y )/0 2.5 '{ 4/0 2.5 YR .5/8 5 YR 7/4 2 • .5 YR 5/8 gray SLIP dk r;ray red SLIP red cc 23 2,5 YR .5/6 2,5 YR 4/8 2,.5 YR 5/6 2.5 YR .5/8 2.5 YR .5/6 2.5 YR 5/8 red red r~ (Conti~ued on following page) ,_...... 0'\ CHART 1, Continued ORIGINAL COLOR REFIRED TO 9000C variety inner outer core I inner outer core Casa Madalengo1tia Colonial, CI A 7,5 YR .S/2 7,5 YR 5/2 2.,5 YR 6/8 5 YR 6/6 5 YR. 6/6 2,,5 YR 6/8 brown bl•own lt r!!!d reddish yel1.ow reddish yellow lt red CI 1 lO "!R 4/1 '10 YR 4/l 10 YR .5/'J 2,5 YR 5/6 2.5 YR.S/6 2,5 YR 5/6 dk gray dl• gray bro"-n red red red CI 5 2.5 YR 2/0 2.5 YR 2/0 2,5 YR 2/0 2,5 YR 5/6 2.5 YR 5/6 2,5 YR 5/6 black black black red red red . l Chiquitoy Viejo Chimu-Inca B 6 i.S YR 4/0 7,5 YR 4/0 ?.5 YR 5/0 5 YR 7/6 . 2,5 YR 6/8 2,5 YR 6/8 dk gray dk gray gray reddish yellow lt red lt red • D 25 2.,5 YR 5/6 2,5 YR 4/4 2.5 'X'R 5/6 2.5 YR 5/8 2,5 YR 4/6 2,5 YR 5/8 red reddish brown red red red red ·R 8 2.5 YR 5/6 2,5 Ya 5/6 !i YR 4/4 2.5 YR 5/6 2,5 YR 5/6 2,5 YR 5/6 red red reddisn 'tlrown red red red 1-' 1-' '-.J 118 CHART 2 Porosity measurements for the Moche Valley site collections. Finewares are preceded by {F) GRAMALOTE - INITIAL PERIOD CERRO ARENA - SALINAR Early Intermediate variety -% Period lA 5.1 2 11.8 variety ~ 4 12.8 1 DEC 20.6 {F)S 35 8.8 1 20.6 (F)SG 24 12.2 3 21.6 (F)S 28 15.4 I s 33 16.2 {F)S 34 16.2 (F)SG 15 16.9 CABALLO MUERTO - CUPISNIQUE s 30 17.7 Early Horizon (F)S .32 17.9 CA 1 18.2 7 12.8 SG 4 20.4 -28 12.9 SG 20 20.4 (F) 8 14.5 (F)SG lOA 20.8 (F)l8 15.2 {F)S 27 20.9 9 15.8 SG 6/7 21.1 17 16.5 SG 19 21.3 11 16.8 (F)S 26 22.2 31 17.3 SG 3 22.8 4 18.1 SG 5 24.0 22 19.6 SG 1/2 24.4 14 19.9 SG 25 24.4 5 20.9 (F)SG 8 24.5 32 22.4 SG 11 27.6 30 23.1 s 29 28.0 21 23.4 s 31 29.6 26 23.6 33 27.8 2 30.3 (Continued on following page) 119 CHART 2 (continued) CERRO OREJAS - GALLINAZO GALINDO - MOGHE V Early Intermediate Per~od Middle Horizon variety 1! variety ~ 24 2.0 (F) 8 A DE 15.6 15 11.4 5 PL 17.5 (F)l7 12.4 3 A DE 18.0. 1 15.0 (F) 6 DE 18.4 11/llA 16.2 3 PL 18.9 18 18.2 4 A PL 19.5 3 19.2 (F) 8 DE 20.0 19 19.7 5 DE 21.8 4 19.9 4 PL 21.9 (F) 8 21.2 4 A DE 22.7 (F)l4 21.6 3 DE 23.6 21 21.7 1 23.8 2 21.8 3 A PL 25.9 (F)l3 22.4 2 PL 26.8 (F)l6/16A 24.6 7 DE 26.9 23 25.8 4 DE 29.2 (F) 6/7 27.2 2 DE 36.8 10/lOA 27.8 5 28.9 12 29.7 20 30.9 22 42.1 VARIOUS SITES PYRAMID SITE - MOGHE EARLY GHIMU Early Intermediate Period Middle Horizon 8 16.4 3 19.1 (F)l5 17.6 (F) 9 21.1 (F)l7 18.5 15 21.3 - 5 19.7 16A 21.7 1 19.8 12 22.3 4 19.9 7 23.0 (F)l6 22.2 17 23.8 12 23.9 3A 24.6 (F)l8 24.4 2 24.9 9 24.9 5 25.0 (F)l9 25.0 6 25.4 11 25.2 (F) 8 25.5 3 25.6 11 26.0 2 26.8 14 26.1 7 27.2 13 26.4 (F)20 28.0 2A 26.7 . 6 29.4 1 27.4 (F)l4 :35.8 16 27.7 13 39.2 (F) 4 31.9 10 79.3 (F)lO 33.6 (continued on following page) 120 CHART 2 (continued} CHAN CHAN - CHIMU CHAN CHAN (LABRIENTO} Late Intermediate Period CHIMU Late Intermediate Period variety ~ variety ~ 10 19.6 22 12.8 18 20.7 9 17.9 22 21.1 21 18.5 20 21.1 15 A 19.6 (F) 3 21.4 19 20.6 9 22.3 6 A 21.1 7 A 22.9 14 21.5 (F) 1 23.3 (F) 3 21.7 14 23.5 15 B 21.9 13 23.6 (F) 1 23.7 21 23.8 2 A 23.7 27 24.3 10 23.8 11 24.4 18 A 24.9 17 A 24.4 13 2 .5 6 24.6 6 24.7 8 25.3 4 24.9 2 26.2 12 A 25.4 17 27.3 17 25.4 18 A 28.2 8 25.6 4 29.5 7 25.8 (F)26 30.3 .. 23 26.1 15 30.8 12 26.5 16 32.0 7 A 28.7 5 34.6 5 28.8 23 37.4 16 29.0 12 38.8 15 31.0 11 31.2 18 32.9 27 33.1 20 33.5 (F)26 39.5 (F) 2 43.0 (continued on following page) 121 CHART 2 (continued) -- CHIQUITOY VIEJO CASA MADALENGOITIA CHIMU - INCA COLONIAL PERIOD Late Horizon variety ~ variety ~ (F)D9 9.8 5 14.5 (F)R18 10.2 D22 18.0 D19 10.7 17 18.4 (F)D2 12.9 7 A 18.7 D7 15.7 (F)F1 21.5 (F)R16 17.5 (F) 1 21.5 (F)D25 17.6 6 A 21.8 R8 18.2 19 22.5 R17 18.4 D5 22.5 (F)D27 18.5 D14 22.8 D20 20.8 23 22.9 R19 21.4 L 24.5 R2 22.7 F 24.7 R3 22.7 8/9 25.0 R11 24.3 (F)D1 25.6 R14 24.5 6 26.6 (F)B22 24.9 A 26.8 (F)R21 25.1 14 27.1 R7 25.2 D9 27.3 (F)B20 25.3 J 27.6 (F)B21 25.3 16-A 30.7 R1 26.0 R13 26.1 R6 26.3 (F)B16 26.4 (F)B23 26.9 (F)B24 27.7 (F)D26 28.0 D8 29.0 (F)D22 29.7 {F)D28 30.4 B6 30.5 B3 30.9 B2 31.0 B25 31.1 B14 45.7 122 ,-- ., I I i ! ! Ii CHARt ) PIRING TRENDS BY SITE COLLECTIONS PI~«A~ 0 0 0 0 .. N ...... ~roo oR ORIGI'IA.L .."' "' "' INJ SITE. PORCSITY < I I I I I I I I I I I I I I I I I I I• I I I I I I I I I I I 1""'1 5.1 • C!U.or.uon 11.8 (no tine- 12.8 • .,.rae} 20.6 • 21.6 • • ~--- CABALLO IIUERTO £UPJSNJQUE 8 14.5 • 18 15.2 • CERI!O ARENA SALPIAR 8,8 SG2nz 12.2 • s 28 15.4 • S34 16.2 • • SG15 16.9 • CERIIO OR"'...J AS GA.LLIIU.ZO G 8 21.2 • G 1~6A 24.6 • G 6 7 27.2 • PYI!A..'IIIIO SITE li!OCHZ • 1.5 17.6 r:Iv " 20 28,0 • .. 18 )6.2 • • GALINDO 8A Dl!! 1.5.6 • f!OCKl!! V 6 DB 18,4 • Ill 19 2.5.0 • (!lOT CHA!I CH.•.!I) EARLY CHI!l'U 9 21.0 8 25 • .5 • 14 26.1 • 4 1. • 21,4 CHAif CHAN 1' 2),) • II!IDOL~ CHI".U • tAT!'! CHI~ CIWf CHAI'I (LAl!RI!NTO} 1 2).? 11':!001!'! CH!!I'U 26 )9.5 • tATE CHI!fll • 0 ? 9.8 R 18 10.2 • R 16 17.5 • CHIQUITOY 0 25 17.6 • 'f!'!JO 0 27 18.5 • B 22 24.9 • g!I!!!!-JIICA. R 21 2.5.1 • B 20 2.5.) • 1121 2.5.) • B 16 26.4 • 26.9 • 'B 2 27.7 • ' 0BZ' 26 28,0 • 0 22 29.? • • D 28 )0.4 • CASA p 1 21 • .5 "AOA.L!!ICOITU. 1 21 • .5 • COLONIAL 0 1 2.5.6 • \no hnewaree) • I f I I I I I I I I I I I I I I I I I I I I I I I I I I I I I l 0 0 0 0 ... .."' N "'N .... "'...... ------· 123 CHART 4 site and ~y11ure variety original " porosity l!Orosit;y at 20ooc decreasa" ot increase" ot Oramalote GR lA 5.1 4.4 .14 Initial Period GR 3 21.6 .51.3 58 CA 1 18.2 1?.4 4 Caballo Muerto 2 )0,3 20,8 )1 Cupienique 14.5 21.8 ~~h~ 15.2 38.9 ~~ Cerro Arena. (F)24 12.2 21.1 42 Salina!' 16.2. .25.6 .3? (F)~~ 16.2 20.? 2.5 Cerro Orejas ~F)G 8 21.2 23.? 10 Ga1lina~o F)G 16/16A 24.6 2?.8 11 G 24 2.0 31.1 93 .pYramid Site (F~M.15 1?.6 30.8 42 Mocha I - IV (F M 19 25.0 31.2 20 (F)M 20 28,0 31.? 12 Galindo 3A DE 18.0 25.6 30 Mochc v (F)6 DE 18.4 21.8 16 (F)8 DE 20.0 28.1 29 (Not Chan Chan) (F) 8 2,5.,5 21.2 1? E. Chimu (F)lO :n.6 28,6 1.5 14 26.1 27.8 6 Chan Chan (F) 1 23.3 26.6 12 Middle &: late Chimu 2 26.2 24,4 ? 23 37.4 24.9 33 Chan Chan (Labriento) (F) 1 2J.? 26.1 9 Middle & Late Chir~u 1? 2,5.4 32.0 21 (P)26 39 • .5 26,1• .33 Chiquitoy Viejo B 6 )0.,5 :n.s 9 Chimu - Inca. R 8 18.2 19.8 8 (F)D 2.5 1?.6 14.0 20 Casa Mada1engoitia A 26.8 28.4 41 Colonial Period (F)1 21.5 18.0 16 .5 14 • .5 2,5.0 42 124 CHART 5 porosity poroalty " of site and culture variety at £oooc at ll~ooc decrease Gramalote GR iJ. 4.4 18,? (increased) Initial P9riod GR ) 51.4 51.0 0 CA 1 1?~ 26.0 (increased) Caballo Muerto 2 20.8 4.5 ?8 Cupisnique fF) 8 21.8 15.8 27 F)l8 ,38.9 21,1 46 Cerro Arena (F)24 21,1 18.5 12 Sallnar J) 25.6 2),9 ? (F)J4. 20.? . 6,8 6? Cerro Or·ejas (F)G 8 . 2),7 9.8 59 Galllnazo (F)G 16/16A 27.8 14,0 50 G 24 )1,1 o.o 100 Pyramid Site (F)M 15 )0.8 12.4 60 Mocha I - IV (P)M 19 )1,2 ),6 88 (P)M 20 )1.7 16.8 47 Galindo )A DE 25.6 11.4 55 Moehe V (F)6 DE 21.8 15.4 29 (P)8 DE 28,1 ),6 67 (Not Chan Chan) (F) 8 21,2 o.o 100 E. Chimu (F)10 28,6 2.9 90 14 27.8 2.9 90 Chan Chan (F) 1 26.6 9.9 6J Middle & Latu Chimu 2 24,4 9.8 60 2) 24.9 11.9 52 Chan Chan (labricnto) (F) 1 26,1 16.6 )6 J,liddl!! & Late Chimu 17 )2,0 1.5 . 95 (F)26 26.4 18,1 )1 Chiquitoy Viejo B 6 )).5 11.? 6.5 Chimu - Inca R a 19.8 o.o 100 D 25 14.0 6.8 51 Casa Madalengoiti~ A 28.4 17.5 )8 Colonial Period (F) 1 18,0 4.1 77 5 25.0 8.0 68