The Use of the Harris Matrix to Document the Layers Removed during the Cleaning of Painted
Surfaces
Jose Manuel Barros Garcia
A significant difficulty in documenting cleaning processes for polychromed works is the overall
recording of the stratigraphy of the structures involved, especially the non-original layers, which
arc composed of heterogeneous materials deposited on the surface. When these layers are removed,
information about their stratigraphic configuration disappears. Archaeological stratigraphy
provides interesting methods to document stratigraphic sequences. The Harris Matrix is a diagram
that describes the chronological relationships between layers and other stratigraphic units.
Adequately fitted, the Matrix can be used to record the removed layers and to contribute to a more
accurate documentation, which will allow a future researcher to know what the state of the
polychromed work was before the cleaning process.
INTRODUCTION
In 1987, Bergeon and Perier-d'Ieteren explained the necessity to extend the usual stratigraphic study
of pictorial layers — that is, the ground and paint layers — to the materials deposited later, such as
varnishes, overpaint, and layers of glue [1]. They suggested that a very important project was the
creation of a specific method to compare both the paint layer structure and the surface deposits for a
great many polychromed works. However, in spite of advances in stratigraphic studies, no
systematic work has been carried out to standardize the documentation methods used to record
information, a step that would allow an analytical comparison between structures. This is especially
critical in relation to the non-original materials deposited on the painted surface of artifacts.
Stratigraphic studies have usually focused on the original pictorial structure (OPS). However, only
in the last few decades has it become evident that conservators have a clear interest in
understanding the configuration of the materials deposited subsequently. These superposed layers
are studied because the conservator needs to collect data about their composition. But the conservator also needs to know their configuration, that is, how these diverse materials are distributed.
This constitutes an essential piece of information in, for example, the cleaning process. A group of
layers containing the same materials may show very different arrangements, which will determine
the design of particular cleaning systems for each structure (Figure 1). A meticulous reading of the
deposits, isolating individual materials, as demonstrated by Wolbers and other authors influenced
by his work [2-6], is a key factor when designing cleaning systems. Successful cleaning is only
possible with a thorough understanding of the complexity of the surfaces.
To record and manage this stratigraphic information the conservator needs an appropriate method.
Since the 1970s, conservators have made use of a methodology of archaeological origin in the study
of the numerous layers of polychromy deposited on sculptures [7-9], and the
Figure 1 Different arrangements of three materials (oil, protein and resin) deposited on an
original paint layer.
work of Ballestrem in this field has been extremely important [10, 11].
The present study goes a step further in the use of archaeological methodology in the conservation
of polychromy. In this paper, it is suggested that the Harris Matrix is used to record the non-original
layers (the deposits collected on the surface) removed during cleaning. The Matrix was invented by
the archaeologist Edward C. Harris to record the stratigraphic sequences of archaeological sites in
diagrammatic form [12]. This diagram can be used with any stratified structure and the method has
been employed in the analyses of buildings, rock art, wall plasters and in many other diverse
situations where stratigraphic principles come into play. Here, the author presents a first approach in
the development of Matrix applications for the documentation of layers in polychromed artifacts.
NON-ORIGINAL LAYERS ON POLYCHROMED WORKS
Throughout its life a polychromed work undergoes the application of many types of new layers on
its surface, including overpaints, new polychromy, varnishes, adhesives and consolidants. The main
aims of these interventions can differ greatly, although for the most part their purpose is to
reinterpret the work, changing its formal, stylistic or iconographic content; to mask the presence of
missing areas of colour; to protect the surface; to modify gloss; or to consolidate detached areas.
Furthermore, all kinds of materials, which can be referred to generically as dirt, are deposited
accidentally. This variety of types of strata implies that the materials which make up the layers
deposited later in the life of an object can be highly heterogeneous in their composition (for
example natural or synthetic resins, oils, natural waxes, proteins, polysaccharides, and materials
deposited accidentally, such as organic or inorganic particles, fungi, etc.). The sediments are not
generally deposited in a homogeneous manner, but on the contrary as layers of different
thicknesses. Furthermore, successive cleanings are often carried out incorrectly and unevenly,
which adds greater complexity to the configuration of the structure [13]. In this way, remains of old
deposits are enclosed within other layers applied later and losses (significant or not) are filled with
new layers. The result is a complex superposition of strata of a heterogeneous nature (Figure 2). It
can be extremely difficult to understand the configuration of these layers unless the conservator has
access to an internal analysis of the structure.
These non-original strata are usually removed for different reasons during cleaning: because they
cover up the original paint, because they are degraded, or because they promote degradation
processes in the original materials. Although it may be necessary to remove these elements, it is
also necessary to document as much information as possible about the strata and their configuration.
THE STRATIGRAPHIC UNITS
The stratification process is a cycle of both accumulation and erosion or removal of materials. This
process causes the stratified structure to be divided into positive or negative stratigraphic units, the
smallest units of archaeological identification. The positive units are the layers of deposited
materials. The negative units are erosions or gaps — loss of materials. These are the basic elements
that shape the stratigraphic construction.
Positive units
A layer or stratum is, from the standpoint of stratigraphy, a portion of relatively homogeneous and
indivisible material. The surfaces of strata are named 'interfaces'.
Figure 2 An example of the formation of a structure of non-original layers: (a) the painted surface
receives a coat of varnish; (b) inappropriate cleaning partially removes both the varnish and paint
layer; (c) the damaged area is overpainted and a new coat of varnish is applied; (d) a layer of dirt
covers the varnish.
These have the same stratigraphic relations as the layers and are recorded as a single unit (the layer
and its interfaces) [14, p. 74]. Identification of the interfaces is an essential step in every
stratigraphic study and also in cleaning. To identify the presence of a partition between several
layers is usually the only suitable way to establish the feasibility of cleaning.
Negative units
Negative units are formed through the partial destruction of pre-existing strata. They are
stratigraphic units in their own right since they correspond to recognizable events. They have their
own stratigraphic relations with other units and their own limits and outlines [14, p. 85].
The division into stratigraphic units
Stratigraphic units are seen as 'units of action'. That is to say, every unit corresponds to a single
event that we can understand through observation and analysis. It is only through the division into
stratigraphic units that we can know the reality of the events that define the composition and
configuration of a given structure.
To divide a stratigraphic structure into its units implies an accurate study of the processes of
deposition and destruction which have formed those same units. However, this division has a
somewhat arbitrary nature. A thin layer of dirt deposited on a surface may be enclosed within a
layer of varnish applied subsequently. This creates a single stratum, although both materials and
actions are obviously different. The conservator must stop the identification process of the basic
elements at some point. Stratigraphic units are both objective realities and a result of the
conservator's analysis [15].
THE HARRIS MATRIX
The Harris Matrix, invented in 1973 by the archaeologist Edward C. Harris, is basically a
representation of the stratigraphic sequences of archaeological sites in diagrammatic form. First
published in World Archaeology in 1975 [16], the axioms and methods necessary for correctly
recording the archaeological stratification and its display in Matrix form were published in the
Principles of Archaeological Stratigraphy [12], a text which has changed the nature of
archaeological studies. This book has been re-issued [17] and has been translated into Italian,
Slovenian, Polish, Spanish [14] and Japanese. Other books and articles of great importance for an
understanding of the possibilities of the Harris Matrix as a tool for documentation have also been
published [15, 18-20].
For a complete understanding of the archaeological methodology and the principles on which the
Matrix is based, the four 'laws of stratigraphy' ought to be explained [14, p. 52]; the order in which
these laws are listed below merely follows the needs of this paper.
The first presupposes the formation of strata horizontally due to natural forces such as gravity. Any
stratum deposited in a non-solid state will tend toward a horizontal position. Strata which show
sloping surfaces were originally deposited that way or lie like that due to the shape of a pre-existing
hollow.
The second law states that any positive unit will be originally delimited by a hollow or its thickness
will decrease progressively towards the edges, finishing in a wedge. This principle is also applied to
negative units: if any extreme of a positive or negative unit shows a vertical face, this means that
part of its original extension has been lost.
These first two laws are fundamental for archaeological sites but do not have so great an interest in
the study of polychromed works. However, the following two laws are of great importance to the
approach of this paper.
The third law involves the continuation of the order of deposition between any given layers: in a set
of stratigraphic units (in their original state), the upper units are later and the lower are earlier. A
unit is deposited onto another, or is created by means of removal of a preexisting stratification
section.
The fourth allows the recording of stratigraphic sequences in diagrammatic form: a stratigraphic
unit is properly located in the sequence between the lower (or earlier) ot the units which cover it and
the upper (or later) ot the units covered by the stratigraphic unit (the units must have physical
contact). Other relationships of superposition are considered redundant [14, p. 58] (Figure 3). By
this means, the significant relationships are fixed, that is to say, those that represent the relative
sequence of the units. Only those relations that mark the development of the stratigraphic structure
in the course of time are important.
Figure 3 The fourth law of stratigraphy allows a simplification of the stratigraphic sequences
through the elimination of redundant relations in scheme (a) to give scheme (b).
Figure 4 The three types of relationships between units described in the Matrix: (a) the units do not
have a direct stratigraphic relationship; (b) the units are superposed; (c) the units are
contemporary.
These relations are the basis of the Matrix and allow the construction of stratigraphic sequences.
Basically, the diagram describes the chronological relationships among the stratigraphic units. In a
Harris Matrix the units are represented as numbered rectangles. When a unit is recognized, its
number is registered and then it is situated on the diagram, according to its stratigraphic position.
The numbers allocated to stratigraphic units are merely labels, giving a unit a name, and do not
describe chronological or any other type ot relationship between units. It is important to note that
the Matrix is built up from top to bottom, that is, from the later (or outer) to the earlier (or inner)
units.
The relationships are drawn as lines and the position of the connected rectangles describe three
types of relation between units [14. p. 60] (Figure 4):
(a)
units that do not have a direct stratigraphic relationship
(b) units that are superposed
(c) units that are contemporary, originally forming a single unit, but which are now divided.
In this way, the complexities of the strata are reduced to a two-dimensional chronology: a 'before'
and an 'after'. The main objective is to display the stratigraphic elements in their relative sequential
order (Figure 5). A
Figure 5 Stratigraphic units displayed in their relative sequential order (a→ b→ c → d → e).
stratigraphic sequence may be uni-linear or multi-linear. In a uni-linear sequence, the units form a
simple chain ot chronological events. The multi-linear sequence develops separate lines of
evolution and is composed ot a series of uni-linear sequences that are not joined by links of
superposition (Figure 6).
APPLYING THE HARRIS MATRIX TO POLYCHROMED WORKS
The Harris Matrix was designed for use in archaeological sites, so its application to polychromed
works may not seem particularly feasible. It must be remembered that the Harris Matrix is now used
in many different fields, such as in the study of wall plasters, and that, in general, it can be used in
any situation where the principles of stratigraphy come into play [20].
Figure 6 (a) Uni-linear and (b) multi-linear sequences.
Of course there are notable differences between the application of stratigraphy in archaeological
sites and its use in polychromed works. The materials used, the thickness of the layers, their
characteristics and the factors which regulate the processes of deposition are very different. If we
focus on the non-original layers on polychromed works, that is to say, the main subject of this
paper, we find that they can be very thin layers which are difficult to observe because they are
translucent, discontinuous or altered (powdery or cracked, for example). It may also be difficult to
observe the separation between two layers, perhaps as a result of partial absorption of a stratum by
another or there being little difference in colour and texture. Some deposits may appear as stains,
splashes or fragments of previously removed layers. The materials deposited do not always appear
as a broad, homogeneous, continuous stratum, clearly distinguishable from other strata.
However, despite these problems, the Harris Matrix can be used with layers of several metres,
centimetres or even microns thick. The difficulties which may arise in the identification of
stratigraphic units when working with layers of varnish, overpaints or remains of adhesive do not
invalidate the use of the Matrix as we are working within a stratigraphic context in each case.
That we may be unable to identify or establish the relationships among certain units does not mean
that we should not try to record the maximum amount of data concerning the configuration of the
deposits. In some cases, recognition of the interfaces may seem almost impossible, in much the
same way as would establishing a chronological relationship between two layers which are not in
physical contact with each other. Defining the nature and extent of negative units can present some
problems, although they can generally be recorded with adequate accuracy (Figure 7). These
problems, although on a different scale, are also found in other stratigraphic studies [20, p. 49].
In contrast with the original layers, a stratigraphic study of the materials deposited can be carried
out as they are removed during cleaning. This allows a great deal of information, which is not
always easily accessible merely by observing the surface or from studying cross-sections, to be
gathered. Stratigraphic study and cleaning are two processes which necessarily go together, hand in
hand.
In this respect, both the analytical ability of conservators and the selectivity of their cleaning
techniques are factors of great importance in the process of separation. To remove each deposit
individually without damaging the remaining layers, the cleaning agents must be very selective.
This aspect is also fundamental from the point of view of being able to control the process.
Figure 7 Diagrammatic representation of the locations of two stratigraphic units. These units
(labelled 2 and 3) correspond to two areas where a stratum of drying oil, which had been applied
onto the original painted surface (OPS), was partially removed on a previous occasion. Detail of
the 'Ascension of Saint John the Evangelist' by the Maestro de San Lazaro (sixteenth century,
Convento de Santa Clara, Gandia).
CONSTRUCTING THE STRATIGRAPHIC SEQUENCE
The construction of a stratigraphic sequence which records the non-original layers removed in the
cleaning of polychromed works can be summarized in two main phases, although these must be
considered as dependent on each other: the first would be the identification of the stratigraphic units
and the second would concern the interpretation and recording of the relationships between them.
Identification of the stratigraphic units
The information displayed in the Harris Matrix can be obtained via four main sources: examination
of the artifact, analysis of samples, preliminary cleaning tests, and also through the cleaning process
(Figure 8).
Figure 8 The four methods used to obtain stratigraphic information: (a) examination; (b) analysis
of samples; (c) preliminary cleaning tests; (d) cleaning.
Examination of the work should be carried out with magnifying equipment, and with all those
techniques considered appropriate. A careful observation of the work in raking or reflected light, for
example, will allow the degree of heterogeneity of the deposits on the surface to be studied. If, for
example, there is a smooth and glossy layer of varnish and an area which is matt, or with a
particular texture, it can be inferred that there is a deposit on the varnish. This simple identification
of a change in the continuity of the surface (gloss and texture) is important, because it shows the
presence of a stratigraphic unit superposed on the varnish, although at first the composition of the
deposit may not be known. It should also be noted that the variations of the surface are a result of a
combination of variations in the original pictorial layers, the non-original deposits and the characteristics of the support. This means that the conservator must be extremely careful when interpreting
differences in colour, gloss, texture or any other aspect studied [21]. Conservators also have at their
disposal other techniques such as examination by infrared reflectography, ultraviolet fluorescence
and X-rays, to name a few. Examination under ultraviolet light, in particular, has been used for
decades as a straightforward way to study the surface, as different materials may exhibit different
colours and intensities of fluorescence [22, 23].
The next steps, namely the analysis of micro-samples [2, 3, 24-26] and carrying out preliminary
cleaning tests [6, 9, 27], are planned on the basis of the information obtained during the
examination of the work. Although it is not the aim of this article to deal with the study of samples
or cleaning test methodology', it must be said that in general terms the fundamental principle is
always to obtain the most information with the least removal of material.
Lastly, during the cleaning process, the conservator can complete the study while removing each
non-original layer individually. Stepwise removal allows optimum control and safety during the
operation, with the added benefit of obtaining the maximum amount of stratigraphic information.
From these four stages we can record a group of stratigraphic units, part of which can be seen in the
example in Figure 9. The units collected in this Matrix are probably not all those which formed the
non-original deposits, but they are those which have been recognized on the painting shown in
Figure 10. For example, unit 049 (Figure 9) corresponds to an overpaint with a medium comprising
a mixture of triterpenoid resin, wax and drying oil. The presence in this overpaint of cadmium red
and barium sulphate clearly indicates that
Figure 9 The third of the three sheets that contain the Matrix for The Crowning with Thorns' by
an anonymous artist.
it is not an original layer. The layer has been removed individually, giving rise to the appearance of
new units: a layer of isolating varnish, filler, lacuna and an older overpaint. Cleaning by means of
removing one unit at a time allows the identification of units which do not appear in the crosssections (Figure 11), as these show-only information for a very limited area.
Figure 10 The Crowning with Thorns', painted by an anonymous artist during the first half of
the eighteenth century (2.36 x 1.89 m), Universitat de Valencia (UV0030). Before treatment.
Figure 11 Photomicrograph of a sample from The Crowning with Thorns': layers 1, 2 and 3
are original paint layers; unit 207 is a varnish, unit 203 an overpaint, and unit 049 another
overpaint. Photograph: Arte-Lab, S.L.
Figure 12 Recording sheet for stratigraphic unit 164.
The information collected in the Matrix is complemented by recording sheets that describe the units
and by maps showing the location of the different units. Each unit has its own recording sheet
which gathers together all the information obtained: description, composition, or any other data
which are considered relevant. Figure 12 shows the recording sheet used by the author for one of
the stratigraphic units seen in Figure 13, although this is a provisional model, partially based on
those used in stratigraphic archaeology. When there are a number of units with similar
characteristics occupying the same stratigraphic position, these can be recorded as a single unit
when it would not make sense to record them separately, e.g., a group of wax drops.
The maps are diagrammatic representations of the surface (Figures 5 and 7) showing the location of
stratigraphic units (lacunae, overpaints, etc.). The use of recording sheets and diagrammatic
representations will be the subject of a forthcoming publication.
Interpreting and recording stratigraphic relationships
The interpretation and recording of stratigraphic relationships are based on recognizing the
stratigraphic
Figure 13 Detail of The Crowning with Thorns' showing units 164 and 169.
relations among the edges or boundaries of each unit. The units can be placed in the Matrix as they
are identified, starting from the top and working down, just as the cleaning process starts from the
outermost layer and advances towards the original painted surface. Therefore, the innermost units
will be the oldest and the outer units the most recent. As described above, there are three types of
relationship, which can be seen in Figure 9. Units 048 and 043 do not have a direct physical
relation, units 048 and 214 show a relationship of superposition in which unit 048 is the most recent
layer, and units 207 and 226 formed part of one unit which has now separated.
On the recording sheet corresponding to each unit, its stratigraphic situation is shown, with all the
physical relationships indicated. In order to record the non-original layers in polychromed works, it
might be important to display the more significant physical relationships, even if they prove to be
redundant with respect to the sequential order. This will allow the construction of particularly
interesting partial sequences. In other words, some sequences can be selected, which will allow an
understanding and recording of the initial situation in a more exact and complete way (Figure 14).
The construction of the stratigraphic sequence presents an opportunity to reassess our understanding
of the object and the coherence of our interpretations [20, p. 153]. In the stratigraphic diagram, the
units (both positive and negative) that have been identified are laid
Figure 14 (a) The Matrix shows the stratigraphic sequence of the units displayed in the schematic
of the cross-section; (b) some unilinear sequences record important physical relations between
certain units.
out in such a way that relative chronological relationships are shown in schematic form. In Figure 9
a group of units has been shaded grey, and a possible alternative location in the stratigraphic
sequence suggested. It is, in fact, a layer of varnish, situated under a stratum of old overpaint
(Figure 11). However, we do not know for sure if the layer preceded, or was subsequent to, losses
from the paint structure. If it were the former, it could be an original varnish. However, the results
of the study have not been conclusive.
Other data displayed in the sequence
The central element in the construction of the Matrix is the position of the units in the sequence.
However, the stratigraphic sequence also allows further data to be displayed, a process that can be
carried out in such a way that the information is recorded with great ease. The conservator can
insert many levels of information about the structures, the different units and cleaning methods
(Figure 15). Thus, for example, data about the materials which compose each layer may be
incorporated in the sequence through text, symbols, or reference numbers.
The Matrix also allows both the polychromy (or original pictorial layers) and the material deposited
later
Figure 15 An example of a Matrix containing data on the sequence of units, their composition and
cleaning methods.
Figure 16 Photomicrograph of a sample from a sixteenth-century painting: (1) ground; (2) glue
priming; (3) original paint layer; (4) varnish and other layers deposited on the surface.
Photograph: Arte-Lab, S.L.
to be displayed together in a single sequence. This is particularly important when the polychromy
has a complex structure and a very heterogeneous composition. Overpaints and other non-original
layers will generally be deposited on the painted surface, although they may also be deposited on
the ground and/or the support when the paint layers have suffered detachments or because part of
the ground or support has deliberately been left exposed by the painter. In such cases it is advisable
that these sequences be recorded (Figure 14).
Furthermore, other structural data which may be considered appropriate can be included, such as the
type of interface between superposed layers. In this case, the information would describe the links
between units, for example, between the original painted surface and the deposits that are in close
contact. This descriptive element could be particularly useful in those cases where two layers are
merged together in such a way that it is impossible to establish an interface (Figures 16 and 17),
although it is unable to show more subtle relations.
STRATIGRAPHIC RECORDING AND HISTORICAL STUDY
Non-original layers are significant evidence of material history [28]. Every event leaves its trace —
restorations, transformations, or accidents. The deposits which collect on the surface are specifically
related to the conditions under which the artifacts have been preserved, and environmental
conditions or certain processes of degradation can be recognized through this valuable method of
studying the object [26, 29]. Analytical data, collected
Figure 17 Stratigraphic sequence corresponding to Figure 16. During the cleaning process three
stratigraphic units were identified. These corresponded to non-original layers that, in Figure 16,
appear as only one stratum (4). The interfaces between units 2 and 3, and between unit 3 and the
painted surface cannot be seen, since the varnish and other materials have intermingled and
penetrated into the porous layer of paint (the numbers in the Matrix are not the numbers used in
Figure 16).
using appropriate techniques, are an invaluable source of information to help understand both the
history and the conservation conditions of the polychromed work.
In sculptures covered by many layers of polychromy, the stratigraphic information allows a
reconstruction ot the evolution of decoration through time [8-11, 30|. By means of stratigraphic
study, a relative chronological sequence of material deposition can be constructed. The presence of
some components — like certain pigments or other materials, such as synthetic resins, which can be
dated more easily — will provide more accurate chronological data. All this historical information
can be recorded, and subsequently studied, by means of the Matrix.
Once the Matrix is finished, the information can be condensed into 'phases', as shown in Table 1. In
this sequence, all the available information about the original pictorial structure, obtained by the
study of cross-sections, has been added to achieve a more complete overall view. These phases
permit the observation of different events, for example varnishing or overpainting. Studying the
units from 'The Crowning with Thorns', we can see that two restorations were made in the past
(Table 1). The second restoration is encompassed by phases V to VIII, while the first includes phase
III and perhaps phase II, although, as described above, the inclusion of the latter is only a
hypothesis. In the second restoration, the presence of cadmium red clearly shows that it has been
carried out in the twentieth century. From documentary evidence for restorations carried out in the
last few decades at the Universitat de Valencia, it seems likely that this restoration took place in the
1960s.
Table 1 The different phases into which the stratigraphic sequence of 'The Crowning
with Thorns' has been divided
CONCLUSIONS
The Harris Matrix is a means to record complex strati-graphic sequences, whatever the origin of the
stratification. This study proposes the use of the Matrix to record the non-original layers deposited
on the surface of polychromed works in a diagrammatic form. The strati-graphic data can be
displayed in such a way that it is possible to understand the configuration of the layers involved.
Undoubtedly, there is, at present, no other more satisfactory method of gathering information from
a stratigraphic structure. Despite the fact that the strati-graphic diagram may seem very schematic, it
is a method which has sufficient flexibility to allow the introduction of variations in the type ot
information gathered, depending on the nature of the data the conservator wishes to record. This is
an important detail that allows the inclusion of ,1 wide and heterogeneous sequence of data
(distribution and composition of materials, cleaning agents employed, kind of interfaces or
unremoved units). Thus, the diagram becomes a synthesis of the fundamental stratigraphic data.
Although not discussed here, this method can be incorporated into a number of computerized
recording systems (there are several software packages designed for representing the stratigraphic
sequences used in archaeology). The stratigraphic information can be recorded in a database, which
will make it easy to compare the structures of diverse works. The results of this study will be
reported in a future publication. To sum up, the Matrix could indeed become a useful tool for the
conservation of polychromed artifacts, but there is still much research to be carried out in this field.
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AUTHOR
JOSE MANUEL BARROS GARCIA received a PhD in fine art from the Universidad Politecnica de
Valencia (UPV); the title of his thesis was 'Objetivos y limites en la limpieza de estructuras
pictoricas' [Objectives and limits in the cleaning of pictorial structures]. He has, to date, 16 years'
experience as a painting conservator in private collections as well as public institutions. He has
published various papers and has lectured extensively on the conservation of paintings and, in
particular, on the theories, techniques and methodologies ot cleaning, these subjects being his main
field of research. At present he teaches in the Departamento de Conservacion y Restauracion at the
UPV. Address: C/ Salvador Giner 8-Puerta 5, 5E, 46003 Valencia, Spain. Email: jmbarros50
@hotmail.com
Resume — Une des difficultés significatives lors ¡te la documentation relative aux procédés de
nettoyage de la polychromie réside principalement dans le relevé complet des couches
stratigraphiques mises en jeu, spécialement pour ce qui concerne les couches non originales,
composées de matériaux hétérogènes accumulés sur la surface. Lorsque ces couches sont enlevées,
l'information concernant leur configuration stratigraphique est perdue. La stratigraphie
archéologique fournit des méthodes utiles de documentation des couches successives. La matrice de
Harris est un diagramme qui décrit les relations chronologiques entre les couches et les autres
éléments. Si elle est convenablement étalonnée, elle peut être utilisée pour enregistrer les couches
éliminées et contribuer à une documentation plus fine, ce qui permet aux futurs chercheurs de
connaître l'état de la polychromie avant le processus de nettoyage.
Zusammenfassung — Eine große Schivicrigkcil bei der Dokumentation des Reiuiguugipwzcsses an
Malschichten ist die vollständige Darstellung der Stratigraphie der Strukturen. Dies gilt
insbesondere für auf der Oberfläche abgelagerte, nicht originóte Schichten, die sich aus sehr
heterogenen Materialien zusammensetzen. Wenn diese Schichten entfernt werden, verschwindet
auch die Information über deren Struktur. Mit der archäologischen Stratigraphie gibt es ein e gute
Möglichkeit diese Sequenzen zu dokumentieren. Die Harris Matrix ist ein Diagramm, das den
chronologischen Zusammenhang zwischen Schichten und anderen stratigraphischen Größen
beschreibt. Entsprechend angepasst kann die Matrix dazu verwendet werden, die entfernten
Schichten aufzunehmen, um so eine Dokumentation zu ermöglichen, die späteren Forschen zeigt, in
welchem Zustand sich das gefasste Werk vor der Reinigung befand.
Resumen — Una de las mayores dificultades a la hora de documentar los procesos de limpieza en
policromías es la descripción de las estratigrafías que presentan las estructuras en cuestión,
especialmente las capas no originales, las cuales están compuestas de materiales heterogéneos
depositados en la superficie. Cuando estas capas se eliminan desaparece también información
sobre su configuración estratigráfica. La estratigrafía arqueológica aporta métodos útiles para
documentar esas secuencias estratigráficas. El diagrama llamado 'Harris Matrix' [la Matriz de
Harris] describe las relaciones cronológicas entre capas y otras unidades estratigráficas.
Adecuadamente empleado la Matriz puede ser usada para registrar las capas eliminadas y
contribuir así a una más precisa documentación de la intervención; esto facilitará, así mismo, a
cualquier futuro investigador el conocer el estado de la obra policromada antes de los procesos de
limpieza.