Chapter Five: Methods by J. David McMahan
A general field strategy, along with
excavation protocols, was established in the 1997 recovery plan
(McMahan 1997:17-19). The complexity of the Castle Hill cultural
deposits, which was not apparent until data recovery was well
underway, presented challenging methodological problems. These
were exasperated by torrential late summer rains, a long history
of recurring construction disturbances, periodic vandalism, and
steep topography over much of the site. Consequently, the original
methods were modified and supplemented to accommodate the realities
of fieldwork (Figure 5.1).
Mapping and Provenience
A metric grid facilitated the mapping of surface materials,
features, surface tests, and block excavations. During the 1995
testing program, archaeologists established a baseline across
the long-axis of the grassy park on top of the hill. With an optical
transit, a primary datum monument was established at the south
end of the baseline (at a sidewalk drain) and assigned arbitrary
x and y coordinates (N100/E100). A secondary datum (N28/E100)
was established at the north end of the baseline (at the opposing
sidewalk drain). From points along this baseline, the grid was
expanded as needed. During the 1995 field season, arbitrary but
internally consistent elevations (z coordinates) were used to
record features and excavation units in the absence of known AMSL
(above mean sea level) elevations. During the 1997 and 1998 field
seasons, when excavations focused on a terrace near the base of
the hill, actual AMSL elevations were calculated by means of a
transit traverse from a cadastral survey monument. Vertical reference
monuments, which were related to AMSL and recorded in a field
log, were established as needed during expansion of the excavation.
The basic excavation unit, against which all artifacts and
features were plotted, was a one-meter by one-meter square. In
most cases, particularly where sediments were deep, two contiguous
units were opened simultaneously to facilitate movement within
the pits. Artifacts were bagged according to unit (northing/easting)
and level. At the excavators or supervisors discretion,
more notable artifacts were assigned individual 3-point provenience
and bagged separately. When expanding block excavations, the excavation
of new units was sequenced to best produce continuous stratigraphic
Most units excavated in 1995 penetrated deep, disturbed sediments
on top of the hill. Because natural stratigraphy at the site had
not yet been defined, soil was removed in arbitrary 10cm levels.
During initial work near the base of the hill in 1997, the use
of arbitrary 10cm levels continued until a better understanding
of natural stratigraphic units was achieved. Subsequent fieldwork
in 1997 and 1998 utilized natural stratigraphic layers where possible,
but reverted to arbitrary 10cm levels when these could not be
discerned. In general, stratigraphy at the site was discontinuous
and complicated due to recurring episodes of construction and
disturbance. In the field, stratigraphic sequences were established
for each individual unit with an effort at consistency with adjacent
units. Stratigraphic units across portions of the site that were
especially complex, as where building ruins overlay or overlap
each other, were correlated from notes and drawings during laboratory
Figure 5.1. An elaborate tarp system was constructed to protect the site from heavy rainfall during excavation.
In 1995, test pits were excavated using a combination of shovel
and trowel techniques with the objective of identifying high-potential
areas. Testing was generally initiated by trowel, with the option
of using a shovel if extensively disturbed deposits were encountered.
Testing was supplemented by the use of a 4-inch-diameter bucket
auger and a 1-inch-diameter soil tube on a judgmental basis. During
1997 and 1998, block excavations were carried out almost exclusively
by trowel. Testing and construction monitoring on the slopes and
summit of the hill in 1997-98 made extensive use of shovels for
identification purposes. Trowels were used when features or intact
deposits were encountered. In 1997, a small Kubota backhoe was
rented to facilitate deep testing along the upper trail. This
tractor, which fit within the trail footprint, was used to remove
disturbed overburden so that underlying deposits could be evaluated.
The sediment removed from test pits and block excavations was systematically screened through 1/4 in. mesh to objectify and maximize data recovery. The use of smaller 1/8 in. mesh, while shown to recover 50% more than 1/4 in. mesh in tests (Reed 1994), was considered unfeasible at Castle Hill due to damp soil conditions and the volume of sediment to be moved. At the discretion of the field supervisor, 1/8 in. mesh was used in some contexts (e.g., intact cultural features) and noted as such. To establish baseline information on the adequacy of recovery, particularly with regard to small beads and similar items, sterile sediment samples were routinely collected for flotation. In the laboratory, the samples were processed with tap water by use of a Flote-tech system. Light (flotable) fractions were collected in .325mm mesh, while heavy fractions were collected in 1mm mesh. Sorting of heavy fractions in the laboratory suggested no significant loss of diagnostic artifacts, including beads, in the ¼ in. screens. Artifacts from the samples, along with charcoal, faunal, and bulk samples, were recorded and packaged for further analysis.
Other specialized field methods were used as appropriate. For example, a four-inch-diameter bucket auger was used to supplement test excavations when a broader sample of the deposits was desirable. During all field seasons, particularly in block excavations, a one-inch-diameter tube-type soil sampler was used routinely for subsurface sampling. A metal detector was also used judgmentally to anticipate the location and/or verification of metal artifacts in excavation units. This was complicated by the heavy volume of metal artifacts in the soil. All artifacts, as well as samples such as charcoal, faunal and bulk samples, were recorded in three-dimensions.
Both the 1997 and 1998 field seasons far exceeded expectations
in terms of site complexity and artifact yield. Although an artifact
count was not available at the close of the 1998 field season,
freight records indicate that more than two tons of artifacts
were shipped to Anchorage for analysis. The majority (about ¾
by weight) were recovered in 1998, and represented more than three
times the quantity anticipated on the basis of 1997 findings.
By the completion of cataloging in 1999, more than 300,000 artifacts
had been recorded. Many of these were organic materials that required
General Laboratory Methods and Protocols
During 1997 and 1998 field seasons, Mount Edgecumbe High School
provided a large science laboratory for project use (Figure 5.2).
This facility was indispensable for the preliminary conservation
of finds, and the staging of materials for shipment to Anchorage.
While an effort was made to catalog some finds in Sitka, most
cataloging occurred after the collection was shipped to Anchorage.
In anticipation that the collection would eventually be accessioned
to the University of Alaska Museum, Fairbanks (see Curation,
below), accession numbers were acquired from the UAF museum in
1995, 1997, and 1998 (UA96.050; UA97.094; and UA98.052). For each
accession, OHA assigned consecutive catalog numbers to artifacts.
These were initially handwritten in a notebook, then entered into
a computerized database along with basic provenience and descriptive
information. During cataloging, artifacts were lightly cleaned
and/or set aside for conservation as appropriate. Organic materials
such as textiles, hairs, fibers, and wood were generally sealed
in plastic bags and placed in a chest freezer to await evaluation
and conservation. Numbers were written directly on durable artifacts
unless prohibited by size or fragility. In some instances, a single
number was assigned to a group of artifacts, such as glass shards,
bagged together from the same provenience. In these instances,
a single number was written on the bag and an artifact count recorded
in the database (refer Appendix 4.2). During cataloging, artifacts
from certain functional or diagnostic categories were set aside
for more detailed analysis. These included ceramics with manufacturers
marks, tobacco pipes, currency, lead seals, beads, buttons, weapons
and munitions, hardware, and Native American artifacts.
Figure 5.2. Mount Edgecumbe High School provided a large science laboratory for the preliminary sorting, conservation, and analysis of artifacts in Sitka.
It became apparent during cataloging that, while SHPO staff
and professional colleagues advocated complete analysis, it would
be ultimately necessary to devise a sampling strategy (refer Appendix
4.3). Under this plan, detailed documentation was conducted for
the above categories (i.e., ceramics with manufacturers
marks, etc.). For the bulk of the collection (glass, unmarked
ceramics, iron, textiles, etc.), 10 of the 162 one-meter-square
units excavated during 1997-98 were selected for quantitative
analysis. Castle Hill lab staff, who were assigned various analyses
based on experience and interest, collaborated in the selection
of units with the goal of: (1) obtaining representative samples
the four identified building ruins and associated trash deposits,
and (2) producing a viable sample of the material of primary interest
to each team member (i.e., ceramics, textiles, fauna, etc.).
In practice, more than 10 units were included in the analysis
of some categories (for example, textiles).
An essential step in processing any artifact assemblage is
the application of cleaning and conservation treatments. Treatments
were applied by project staff under the guidance of, or through
consultation with professional conservators. Brook Bowman, former
State Conservator at the Alaska State Museum (ASM), provided invaluable
assistance in both the field and laboratory. Dr. C. Wayne Smith,
director of the Archaeological Preservation Research Laboratory
at Texas A&M University, provided training in the use of polymers
for the treatment of some organic artifacts (Figure 5.3). Specific
conservation problems were also discussed with individuals representing
the Research and Design section of the Dow Corning Corporation,
the Smithsonian Institution, the U.S. National Park Service, the
McCrone Research Institute, and Parks Canada Heritage Resources
Due to the fragile nature of many of the artifacts, and the long interval between excavation and final disposition, treatment to stabilize some items began at Sitka. The use of the science laboratory at Mount Edgecumbe High School (MEHS) proved important for the evaluation, treatment, and staging of artifacts. At MEHS materials were soaked in distilled water and cleaned or treated as necessary to prevent degradation. Electrolysis cells were set up to process ferrous metals, and in 1998 vacuum chambers were set up for polymer passivation (silicone) treatment of some items. In a few instances, chemical treatments were used in the field to facilitate preservation in place, or in the removal of extremely fragile organic items such as basketry. When structural timbers were exposed in 1998, samples were taken. While there were no plans to collect remaining portions of the timbers, it was desirable to leave them in place for mapping and interpretation until the close of the project. To retard drying and cracking, multiple coats of a low-viscosity acryloid B-72 solution were sprayed on the timbers. In another case, a decision was made to rebury the excavated base of a brick metalworkers kiln so that it could be re-excavated and interpreted at a later time. The design engineers shifted the trail footprint slightly to accommodate in situ preservation of the feature.
After consultation with a research and design chemist at the Dow Corning Corporation, the kiln was sprayed with a prescribed Dow Corning polymer resin. This treatment was problematic, however, in that it formed a white residue on the bricks that had to be removed mechanically. In other incidences, fragile materials such as basketry were dehydrated with acetone prior to removal. When the Ravens Tail robe fragment was discovered in 1998, the item was deemed significant enough that Alaska State Museum staff (Brook Bowman, Janis Criswell, and Steve Henrikson) traveled to Sitka and personally participated in its recovery and initial treatment. The robe fragment, along with an intact spruce root basket, was transported to the Alaska State Museum for professional conservation.
The majority of the collection was assessed and treated in Anchorage (Figure 5.4), where stabilization of the collection was assigned a high priority in the course of overall project completion. All treatments were recorded in a laboratory log for eventual entry into a computerized database. Organic items, with the exception of those treated in Sitka, were kept moist (or in their original condition) in sealed containers during shipment. In Anchorage, these containers were stored in chest freezers until the items could be assessed and treated. Because ventilated laboratory space for chemical treatments could not be secured until April 2000, the freeze drying of some poorly sealed items occurred before treatment. Durable items such as pottery, glass, and lithics were typically washed with tap water and air-dried during cataloging. Treatments of particular material types are discussed below. Specific treatment schedules are reported in Appendix 5.1.
Figure 5.3. Dave McMahan prepares materials for silicone treatment at Texas A&M Archaeological Preservation Research Laboratory. Treated materials included rope and a shoe.
Textiles, Feathers, Hairs and Fibers
Following consultation with the ASM conservator, no chemical
treatments were prescribed for the vast majority of items in these
categories. They were typically soaked and cleaned in distilled
water, with a small quantity of free rinsing conservators
detergent (Orvus paste) if necessary. Textiles were spread flat
to dry, then placed in customized acid-free containers. Many very
small textile fragments, along with feathers, hairs, and fibers,
were simply cleaned, dried, and repackaged according to provenience.
Recovered wooden items included implement handles, carved items,
stoppers, barrel staves, shoe parts, and timber samples. Most
items were small enough to be suitable for a variety of chemical
treatments. Typically, these items were cleaned in tap water followed
by a distilled water bath. They were then frozen in air-tight
containers until a chemical treatment could be applied. The polymer
passivation (silicone impregnation) process was chosen for most
items, and works particularly well with small wooden objects.
This technique was developed for conservation use by the Texas
A & M University Archaeological Preservation Research Laboratory
(APRL) and the Dow Corning Corporation (Smith 1997). This technique,
which was developed largely for archaeological shipwreck materials,
does not require acid-free storage or humidity control. Moreover,
the treatment can be accomplished much faster than with conventional
bulking agents such as polyethylene glycol. A discussion of advantages
and disadvantages of polymer passivation is beyond the scope of
this paper, but specific procedures are described in Appendix
Figure 5.4. The microscopy station at one of four sequential Anchorage laboratories used to process the two tons of Castle Hill artifacts.
Ivory and Bone
Ivory and bone artifacts were typically wet or moist when removed
from the soil. Consequently, these materials were dried very slowly
to prevent cracking. Soon after removal from the ground, ivory
and bone artifacts were cleaned with distilled water, placed in
individual airtight bags, and refrigerated. The bags were monitored
on a daily basis to remove any condensation which had formed with
an absorbent towel. This was continued until no condensation appeared
on the insides of the bags. Unworked bone was simply cleaned with
tap water and allowed to air dry.
Recovered basketry included examples made of spruce-root, grass,
and cedar bark. Most fragments were in very poor condition at
the time of discovery. They were generally wet or moist when uncovered,
and extremely fragile. Because their excavation was very tedious
and time consuming, it was necessary to keep the specimens moist
with a spray bottle until their removal. Larger specimens were
removed by sliding thin metal sheets (from the local newspaper
office) underneath. The specimens, along with soil matrix, were
then wrapped with plastic and immediately transported to the MEHS
field lab. In the field lab, specimens were cleaned and soaked
in distilled water. Residues from cleaning, along with samples
of soil matrix, were saved in the event that they might produce
insights as to the contents of the vessel. One vessel produced
masses of salmonberry seeds. Conservation of most of the basketry
specimens was problematic due to poor preservation. Several specimens
were treated with polymer passivation with mixed results (Appendix
5.1). A relatively complete spruce root basket, believed to be
a cooking vessel, was transported to the Alaska State Museum for
treatment by a combination of PEG impregnation and freeze-drying.
Favorable results have been reported for similarly treated specimens.
Most recovered leather specimens appeared to represent materials
from the repair and manufacture of shoes. These materials were
in varying states of condition at the time of recovery. Fragile
specimens were recovered with the surrounding soil matrix similar
to the basketry described above, then wrapped in plastic and foil.
Most leather specimens were simply placed in plastic bags to retain
moisture. They were then stored in a refrigerator in Sitka. In
Anchorage, the specimens were cleaned with distilled water, placed
in clean airtight bags, and stored in a freezer pending conservation
treatment. The specimens were then treated by the polymer passivation
method following the procedures described in Appendix 5.1.
Recovered metals included iron, lead, copper or copper alloys,
and composite materials. Also recovered were a few pewter artifacts,
a small piece of scrap gold, and U.S. coins of silver and nickel.
The primary method of treatment for iron artifacts, which were
badly corroded at the time of recovery, was electrolytic reduction.
Some iron artifacts were treated by electrolysis in the MEHS field
lab. Electrolysis was then assigned a low priority in the Anchorage
laboratory because a ventilated workspace was not available until
April 2000, and the treatment of organic materials was considered
to be more critical. Through a cooperative agreement with Marc
Haughaboo, a UAA student, electrolysis was continued in Anchorage
during the fall-winter of 2001-2002. Cleaning of the metals revealed
a wealth of new information on the sites iron assemblage
and metalworking activities, but the results of analysis have
not yet been incorporated into a report. The specific procedures
used for electrolysis of the Castle Hill specimens are described
in Appendix 5.1.
In addition to artifacts of ferrous metals, copper and copper alloy artifacts were well represented at the site. While these were in generally good condition, coinage and buttons were often badly corroded or encrusted so that surface details could not be observed. The majority of copper and copper alloy artifacts were simply dry brushed or cleaned with tap water. Some of the more badly corroded specimens were soaked in distilled water and lightly brushed. In a few instances, badly encrusted specimens were cleaned in an ultrasonic cleaner. In these instances, the ultrasonic cleaner was filled with water, and the specimen placed in an inner beaker of distilled water and mild detergent.
Lead artifacts were comprised of lead seals, musket balls, bullet mold residue, and miscellaneous strips. Most were in good condition at the time of recovery, and were simply cleaned in distilled water or dry brushed. One of the lead seals (98.130) was cleaned with 10% hydrochloric acid, however, to expose characters useful in its identification.