Hopewell Archeology:**\
**The Newsletter of Hopewell Archeology in the Ohio River Valley\
Volume 7, Number 1, December 2006**\
------------------------------------------------**

**3. Development of a Protocol to Detect and Classify Colorants in
Archaeological Textiles and its Application to Selected Prehistoric
Textiles from Seip Mound in Ohio. PhD Dissertation, The Ohio State
University, Columbus Ohio, 2005\
**By Christel M. Baldia

The goal of this dissertation research was the development of a protocol
to study colorants applied to archaeological perishable materials such
as textiles even if these colors are no longer visible to the unaided
eye. The protocol is composed of a sequence of non-destructive or
minimally destructive methods designed to yield a classification of the
colorants that were used prehistorically as inorganic or organic and
pigment or dye. This protocol was then applied to selected textiles from
Hopewellian Seip Mound Group in southern Ohio to test its effectiveness
on actual artifacts.

The protocol consists of a succession of analytical methods that have
been adapted to be used with very small sample sizes. If these are
sequenced properly, the efficacy of the protocol is further optimized,
thereby maximizing the acquisition of critical data while minimizing the
need for large amounts of sampling material, and thus preserving the
integrity of the artifacts.

The methods used were forensic photography using different lighting
conditions (simulated daylight, infrared and ultraviolet), optical and
scanning electron microscopy with energy dispersive X-ray analysis
(EDS), and inductively coupled plasma mass spectrometry (ICP-MS) for
elemental analysis. All methods were first tested on replicated
materials thereby establishing suitable parameters for their application
to archaeological textiles. During the course of working with the
replicas, limitations of the analytical methods were discovered and
addressed for their use on archaeological materials, i.e. a limited
quantity of material with an unknown chemical composition. These
materials have potentially undergone degradation processes and could
have been exposed to a variety of contaminants, which all must be
considered during the analysis. For example, the digestion of the
sampled material for the ICP was refined and a more appropriate
instrument was selected based on the results of working with the
replicas.

To reach the goal of using a minimal amount of sampling material, it is
essential that the series of steps within the protocol are performed in
the suggested sequence. One step builds on the previous one with several
key tasks that must be performed before continuing with the analysis.

First, a comprehensive and systematic visual examination of the textile
fragments (obverse and reverse side) must be conducted. Much can be
learned if this is done meticulously. For instance, many details that
had not been expected were discovered when the textiles were turned to
the reverse side. The lighting conditions must be controlled for this
process to guarantee reproducibility. Otherwise, the results will differ
as the lighting temperature differs.

Then suitable textiles that represent types within an assemblage based
on the results of the visual examination are selected. For instance, the
Hopewell textiles were grouped by commonalities in color and physical
condition such as charring. Magnification should be used if necessary so
no details are overlooked while also controlling the lighting.

Next, non-destructive forensic photography is used as a precursor to all
the other steps. Before any other analytical method can be employed, the
photography of the textiles in different lighting conditions must be
performed because it reveals different chemical signatures due to
colorant/substrate interaction even if these are no longer visible. This
optical behavior is used to discriminate areas of diverse chemistry that
can be correlated to colorant application or contamination. Thereby, the
photography facilitates selective sampling of these areas, while areas
of like chemistry do not need to be sampled. Thus, purposive sampling
enables focused stratified sampling, increasing the opportunities for
critical data acquisition while decreasing the need for the copious
sampling of the material.

At this point, particulate matter should be collected. This dust-like
particulate matter could consist of small textile fiber fragments and
contaminants, which gives the first indication to the researcher about
the textiles' state of degradation. The more particulate matter there
is, the more likely the textiles are severely fragile due to degradation
or mineralization. Furthermore, the particulate can give detailed
information about the textile as a whole, and it can be used for optical
microscopy and possibly other analyses that pertain to the continuous
textile such as infrared spectroscopy.

After that, a detailed macroscopic examination, which also should be
done in controlled lighting conditions, must be performed. Information
about the physical state of the fibers can be gained. For instance, some
of the Seip textiles showed many fractured and fragments of fibers
within a yarn structure that still appeared to be intact, therefore
making it very fragile. Furthermore, the colorant penetration and
levelness of color can be determined, and adhering particulate can be
observed.

This should be followed by the sub-sectioning the samples to divide the
materials for further analysis. Subsequently, optical microscopy (OM) of
the sub-samples can be performed to reveal fiber morphology and optical
behavior. Additionally, the particulate that was collected earlier
should be studied. This process should not be hurried since it takes
some time to get accustomed to the samples and to recognize what is
important in these samples. Images of these micrographs should be
collected, and if a digital camera is used, the colors that are seen on
the screen should be calibrated and matched to the colors seen in the
microscope.

Next, scanning electron microscopy (SEM) on the sub-samples should be
performed. One of the strengths of SEM is the ability to capture
detailed surface morphology that may not otherwise be detected.
Furthermore, the great magnification that can be achieved with SEM shows
details such as degraded scales from hair fibers or even the medulla
cells that otherwise cannot be detected by optical microscopy.

While collecting images with the SEM, energy dispersive x-ray analysis
(EDS) of the fibers and all their components, i.e. fibers and
particulate adhering to them should also be performed. The EDS only
gives the relative ratio of elemental composition of fibers and adhering
materials, which cannot replace quantitative analysis. However, EDS is a
good qualitative method to detect elemental composition. EDS constitutes
a key step that allows the evaluation of carbon compared to the zero
baseline, hence indicating the presence or absence of organic compounds
such as dyes. If organic components are present, organic analysis
methods should follow as the next step, while the inorganic path of
analysis should be taken if inorganic constituents are present.
Furthermore, the relative ratios of elements detected by EDS in
different areas of one fiber can be compared to each other, to other
fibers or to the elemental content of the particulate adhering to the
fibers. Thereby, EDS can give information about ratio of organic and
heavy elements, presence of mineral based colorants, the degree and
variability of fiber mineralization, and possible contaminants.

For the inorganic path of analysis, such methods as ICP-MS/OES or
LA-ICP-MS can be used. For these analyses, the potential problems that
may occur during the digestion process that prepares spectrometry
samples to be analyzed with various potentially suitable instruments
were explored. When dealing with archaeological textile materials, it
must be assumed that the samples will not digest well and that sample
size is very small; and therefore, appropriate adjustments must be made.
Knowing the relative ratio of elements present in the samples from
results of the EDS will ease this process greatly, because appropriate
replicas can be created, and the most likely successful digestion agent
can be chosen to perform the spectrometry. For the organic path of
analysis, such methods as gas or liquid chromatography followed by mass
spectrometry, micro-infrared (IR) and Raman spectroscopy must be
explored. It must be assumed that problems similar to those found when
preparing the samples for ICP-MS will also be found when other methods
such as chromatography are used. Therefore, a successful trial run of
every analytical method with replicated materials must be conducted
before using artifacts. Thereby, subsequent analyses of the artifact
material are most likely to be successful without having to be repeated;
thereby the amount of sample material that is needed will be kept at the
absolute minimum.

Based on an initial visual examination, eleven Seip textiles were
selected and divided into three main color groups: (1) yellow/brown, (2)
turquoise/white, and (3) charred. These are representative of textiles
from the actual assemblage. An extensive, painstaking visual examination
under controlled light and description of the selected textiles' obverse
and reverse sides was conducted. Then both sides of the selected
textiles were photographed in UV, warm and cool visible, and IR
lighting. Based on the findings of the forensic photography, purposive
sampling of the artifacts was conducted. Although the sample sizes were
small, they were representative of the studied textile assemblage.\
The yellow/brown textiles showed some encrustations on the fiber
surfaces and severe fragmentation of the fibers. The fabrics were
constructed of rabbit hair with colorant saturated fibers, which
indicates that dyes were used as colorant sources. There were some
surface deposits, but these could not be linked to the colors of the
fibers. Many of the colored fibers showed no deposits at all.

The elemental composition of the materials from the three colors in this
group did not show any differences between the colors. All colors
contained a large amount of copper, some iron and small amounts of soil
minerals, but they also contained large amounts of carbon, and some
sulfur indicating organic materials in the fibers. It was concluded that
the organic constituents of the fibers had been partially replaced by
copper in a mineralization process. While these textiles were not
reported to have been in contact with copper, they must have been
saturated by copper corrosion products carried by ground water, i.e.
they were near copper albeit not directly adjacent to it. The
encrustations that were observed in the optical microscopy and the
severe brittleness of the fibers support this statement.

The textiles belonging to the turquoise/white group were made of
milkweed fibers that were painted with different pigments. These
colorants had not penetrated into the fibers, but adhered to the fiber
surface. Different lighting conditions during the photography showed
various dissimilar aspects of the patterns, indicating differences in
chemical signatures, and thereby different colorants that had been
applied. The elemental analysis indicated large amounts of copper, and
small amounts of other elements. It was concluded that the white color
was likely kaolin and that some of the other colors had been mixed with
the kaolin or some other types of clay. These textiles were relatively
stable when comparing them to the state of degradation of those from the
two other groups.

The charred textiles were extremely fragile. Patterns no longer visible
in fluorescent white light were visible using photography, and the
simulated daylight showed them best. Ovate motifs in blue, ochre color
and different shades of grey were found. When magnified, it could not be
determined if the colored fibers were penetrated by dyes, because they
are too charred to transmit light. However, different inorganic
particulates adhered to the outside of these colored fibers, and some of
these deposits were iridescent. Large amounts of iron were found in
these colored fibers, but also some copper. The orange/red substance
without any fiber material showed the same spectra as did the fiber but
with lesser carbon peak, thereby verifying that the fibers still contain
some amount of organic material. Fibers without any colorant on them had
less iron and higher carbon and calcium peaks.

Two textiles were identified as composite upon examination. Both
consisted of a combination of several layers of materials: fabric,
leather and matting. Due to the complicated nature of these specimens,
they were only described but could not be addressed otherwise.

**Considerations for Further Research**

All research seems to create as many questions as it provides answers,
and with that it provides room for more work. This research is no
exception. Based on the findings of this study, these are some
suggestions for further work.

1.  For the digestion process to prepare samples for spectrometry,
    ultrasound needs to be applied to the nitric acid/sample mixture to
    achieve better digestion.

2.  Different potential digestion solutions or a combination of these
    such as hydrochloric acid (HCL) and hydrofluoric acid (HF) should be
    explored. Since these can cause problems such as the matrix effect,
    they must be tested with replicated materials.

3.  The phytochemistry of many plants that were used by Native Americans
    has not been analyzed yet. Colorant constituents must be identified
    in such genera that are known to yield dyes such as the native
    Indigofera species.

4.  Standards of North American dye plants and their colorants must be
    created for potentially applicable methods such as Infrared and
    Raman spectra.

5.  The methods to detect organic dye constituents such as micro-Raman,
    micro-IR, GC-MS need to be explored, tested with replicated
    materials and then applied to actual artifacts.

6.  The compositional data reported herein should be explored as to
    which inorganic pigments could have rendered the color to the
    textiles.

7.  Quantitative elemental analysis should be conducted to link the
    colorants from the textiles to potential color producing minerals.

8.  Composite images from the pictures that were taken should be
    created, thereby creating a likeness of what the textile might have
    looked like in the past, but also to potentially differentiate and
    sequence tasks in the production process.

9.  The research done by Song and Thompson on the structures of the Seip
    textiles should be correlated with the chemical analysis and
    microscopy from this research.

10. Trace element analysis of copper artifacts should be done and
    compared to the copper content of the textiles.

11. With the discovery of a bast fiber that had not been identified
    before, new aspects of Seip material culture came to light. This
    bast needs to be identified.

12. The two textiles that were identified as composite herein need to be
    studied in a separate project.

13. The insect piece that was found should be identified, and further
    research should consider when insect infestation of the textile
    occurred.

The dissertation will be available in full length to the public through
Ohio Link in 8/02:\
Click [[here]{.underline}](http://library.osu.edu/) for dissertation.

**In the mean time, please refer to:**

Baldia, Christel M. and Kathryn A. Jakes

2006 *Photographic Methods to Detect Colorants in Archaeological
Textile*. Journal of Archaeological Sciences; in press.

2006 *Toward the Classification of Colorants in Archaeological Textiles
in Eastern North America*. In: Archaeological Chemistry: Analytical
Techniques and Archaeological Interpretation, American Chemical Society
Monograph Series; in press.

Baldia, Christel M, Kathryn A. Jakes and Maximilian O. Baldia

2006 *Polychrome Hopewell Textiles: Dye Technology at Seip Mound in
Southern Ohio* In Proceedings Textile History Forum, Meeting on October
6-7th at the Museum in Winterthur DE.

In preparation:

*Social Implications of the Colorant Application Technology to Textiles
from the Hopewellian Seip Mound Site*. American Antiquity.

*Small Things in Big places: Textiles and Colors from the Seip Burial
Mound Group in Ohio*. In Acts of the XVth UISPP Congress, University of
Lisbon, Portugal, 4-10 September 2006. BAR International Series, Oxford,
England.