Step 4: Laboratory Processing & Analysis
Excavation is only a small part of an archaeologist's work. After excavation, the job of cleaning, analyzing and interpreting begins. In urban archaeology, it is estimated that for every hour of excavation it takes at least 20 hours of laboratory and other work to complete an analysis and report. Often this study and analysis continues for years after the excavation has been completed.
Cleaning Artifacts | Sorting and Marking Artifacts | Crossmending Ceramics and Glass
Cataloguing Artifacts | Faunal Analysis | Analysis and InterpretationMore About Step 4:
A" Case Study: Excavations at the Stabler-Leadbeater Apothecary Shop
A Pictorial Guide to Site Selection and Backgound ResearchArtifacts arrive in the Alexandria Archaeology Laboratory from the sites in bags and boxes labeled according to the provenience, the specific location where an artifact or feature is found in the ground. Ceramics, glass and bones in good condition are washed with a toothbrush in a basin of plain water as detergents can cause chemical reactions that damage the artifacts. Artifacts are then placed in a drying rack for at least 24 hours which insures that the artifacts are completely dry before storage in plastic bags. Other types of artifacts are treated differently. For example, metals are cleaned with a soft, dry brush to remove surface dirt. Wet wood, leather and cloth artifacts are sprayed with fungicide and placed in sealed plastic bags on site until they can be cleaned with a gentle water spray. Once cleaned, it is important to keep all materials from each unit and level together until marked with the provenience.
When dry, the artifacts are inventoried by provenience. First, the artifacts are sorted into categories: ceramics, glass, structural material (window glass, nails), miscellaneous (buttons, pipes, toys), organic artifacts (cloth and leather), bone, shell and seeds. Artifacts in each category are then counted, described, recorded on a sorting sheet and then bagged separately by material within each provenience.
All ceramic and glass fragments are marked with India ink and crow-quill pen with the site and provenience numbers. Artifact assemblages (all artifacts from the same provenience) are studied together, therefore it is important that each artifact is always marked or accompanied by a label. Once marked, the fragments can be removed from their context to be crossmended with fragments from other parts of the site so that individual vessels can be identified and catalogued.
Crossmending Ceramics and Glass
Crossmending is the process of piecing sherds together to form a vessel, regardless of where the artifact fragments were found on the site. The crossmended vessels are held together temporarily with masking tape to reveal the shape. Artifacts are only restored with glue if they are to be exhibited, as restored vessels require more storage space and are subject to breakage. This process requires persistence and an eye for detail and is like doing a jigsaw puzzle. Fragments of each crossmended vessel are bagged separately and given an individual catalogue number.
Cataloguing is the most difficult part of laboratory work. After crossmending, a detailed description of each vessel, along with a sketch or photograph, is recorded on a catalogue card. Alexandria Archaeology has an extensive library of books which are used in artifact identification. Also, study collections which contain examples of the many artifacts found in Alexandria, are used to aid in the identification of ceramics, glass, metal and organic material recovered during excavation. Code books containing standard terminology for use in catalogue descriptions of all kinds of artifacts have been developed. These codes are entered into the computer to enable statistical studies to be carried out and catalogues to be printed.
Faunal analysis, the study of animal bones, is also an important area of study in the lab. Faunal studies can tell us about the diets, types of livestock, socioeconomic status of the people, butchering practices, foodways, as well as the economy of the period. Alexandria Archaeology's faunal analysts have developed a study collection of bones useful in identifying new finds. A code book for faunal analysis can describe the species, element and distinguishing characteristics of each bone.
The next step is to interpret, or find out, what the data mean. One aspect of interpretation is to determine the period or periods of time that the site was occupied. After the ceramics, glass and miscellaneous artifacts are identified and catalogued, artifact groups from each provenience are studied as a unit. These artifacts provide the archaeologist with a point to begin their study of the site. Manufactured products are very useful because their date and place of manufacture can often be identified according to advances in technology and changes in stylistic preferences.
Archaeologists must then estimate when the artifacts were discarded. This is known as the date of deposition. This can be a specific point in time or a span of many years, decades or even centuries. The concept of terminus post quem (Latin for 'the date after which) is used to determine the date of deposition, such as when a layer of trash was dumped into a pit or abandoned well. All of the artifacts which are found together in one level had to have been put there after the date that the newest artifact was manufactured. The date when this most recent artifact was first manufactured is known as the terminus post quem.
Stratigraphy, the study of the layers of the earth that contain artifacts is a relative dating techniques which tell us the order in which things occurred, but not the exact date something happened. Seriation, a graphical comparison of a series of artifact assemblages that have been put in chronological order based on their similarities, is often used when stratigraphy is lacking, such as in surface collections. The sequence of events on the site is determined by analyzing the various types of artifacts recovered from the site.
Absolute dating techniques using scientific methods, such as Radiocarbon (Carbon 14) or Potassium-Argon, are not used in Alexandria and most historic sites. These techniques are expensive, are only used on organic material (ceramics and glass are non-organic), and have a margin of error that can be as much as plus or minus 250 - 500 years. Because manufacturing information and dated samples of artifacts are available for the historic period, these absolute dating techniques are not necessary.
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