Sunday, July 6, 2014

St. George's Processing Days 1-3

This blog may have slipped into a somewhat dormant state over the last month, but the excavation team has not! Over the past few weeks, about a dozen members of the dig team (and some who have recently joined us) have gathered together at the Croton Point Park Nature Center to do some serious artifact processing. Though it is often overshadowed by the drama and excitement of digging, processing can be just as rewarding an experience and is just as important a part of archaeology. It is in processing that we begin to make the pieces that we uncovered all those months ago fit together into a larger picture, like putting together a puzzle.

Processing begins with washing - a lot of washing. Several people have asked the very legitimate question of what all this washing is for, especially when it comes to material that will likely be discarded. The fact is that washing facilitates counting, which is when we identify all of the materials that came out of each level of each test unit and enumerate them - so, for example, twenty pieces of aqua colored bottle glass, or thirty square nails. It's easier to see the color, shape, and any identifying features of an artifact when the dirt has been removed from it. We may even see details that we didn't see before, turning an artifact that would be thrown away into one that we decide to keep.

Of course the question is then, why do we throw certain artifacts away and how do we decide on which ones? The answer to the first part question is that an archaeological excavation typically unearths more material than we could or would want to keep. Whether or not we keep an artifact depends on its relevance to our research questions and questions that archaeologists might ask in the future. For instance, part of our investigation is aimed at locating St. George's Church, which stood in the graveyard from 1761 to 1819, and distinguishing it from the location of St. Mark's Church, which stood from 1852 to 1916. Because they can be assigned to specific time periods, nails can provide a way for us to address these questions. However, only certain nails have diagnostic value in their own right. If the head of the nail has not been preserved, it can be very difficult to determine the technique with which it was made and, accordingly, when it was made. It's still important to enumerate headless nails so that we can tell which areas of the site are likely to have contained a structure - an area where 1,000 nails were found is more likely than an area where three nails were found. But on an individual basis a headless nail is of little value to our research.

The same rules apply to glass. We found an incredible amount and variety of glass, including one whole and some nearly whole vessels. The color and type (bottle or window glass) is important to our study because it can tell us about the activities that took place on the site and how the site was spatially organized. For instance, though we found a copious amount of bottle glass in Feature 5 - in fact all of the glass pictured here is from that unit - we found only a handful of shards in other features (aside from Feature 1, where we found a striking amount of painted window glass). As with nails, it's important to know if there were 1,000 pieces of glass found in one area and three found in another, but a piece of bottle glass that gives no clue as to its date of manufacture or where it came from is of little value on its own. To be relevant to our study, a shard of glass must preserve a part of the bottle that might enable its identification, such as a part of the lip or the base, a seam, or lettering or designs of any kind. Again, all of the shards of glass, whether or not we plan on keeping them, are washed and enumerated by type and color. Only then are certain shards discarded.

It is important to note that the discarded items are not simply thrown out, but kept in a plastic bag for the duration of the processing, until they can be returned to the site. At some point when the processing is finished, we'll dig a hole at the site and bury the discarded material, along with several 2014 pennies to let future archaeologists know that we got there first. We'll also keep a note of what we buried in the records of the dig.

Some items, such as the hundreds of tiny metal pieces we found, will be weighed prior to being discarded. Unlike glass and pottery, we don't wash metal in water, but rather brush each piece lightly with a dry toothbrush before setting them out to dry in the sun. Many of the pieces of metal we found, as well as the nails, are badly corroded. 

We also found a number of bones, but despite the fact that we were digging in a cemetery, none of them are human. Instead they appear to be cow and possibly sheep or goat bones, all with straight cuts indicative of butchering. And naturally, we cleaned the sheep teeth with a toothbrush. 

I took this picture of a cow bone because I was intrigued by the mark on it. I don't know much about bones, so I can't tell if this is a) an injury that was healing, i.e. premortem? or b) a cut that occurred in the butchering process. Luckily I have a connection to a pathologist, who took a look at one of the "bones" we found in the dig earlier this year (it turned out to be a root, not a bone) and may be willing to help us out again.

On the third day of processing we nearly completed the washing of the artifacts from Feature 5. Now all that remains is to wash the remainder of the artifacts and count them, before we can move on to analysis. During analysis we will make a more detailed study of the artifacts, with the goal of determining what they are and when they were made. How we make these determinations will depend on the type of artifact. For example -

-Bottle glass that retains some sort of identifying feature (e.g. lip, base, seam, or embossed lettering or marks) can be assigned to different time periods based on the type of manufacture. The earliest glass bottles were blown by hand, then held by a pontil rod while it was finished, leaving a pontil mark or scar on the base of the bottle. Later bottles were produced by molds that became steadily more streamlined. The earliest molds only created the body of the bottle; the rim was added later, so that the seam of the bottle ends before the rim. Later molds (after 1903) created the entire bottle except for the base, which was added at the end.

-Window glass can be dated based on a formula that correlates time periods to the average thickness of the pane. Much of our window glass is decorated with stencil-painted designs; in addition to providing us with an alternate, easier means of dating, these designs give us an idea of the appearance of St. Mark's Church and the budgetary restraints that may have led to the choice of stencil-painted windows over more expensive stained glass ones.

-Clay tobacco pipes, if found in significant quantities, can be used to date the occupation of a site based on a formula that assigns certain dates to the average bore (or hole) size of the pipes. Individual pipes can be dated and assigned to certain manufacturers based on their form. We weren't lucky enough to find any pipe bowls, which were sometimes lavishly decorated, but we did find one pipe stem that was printed with the name of its manufacturer.

-Ceramics can be readily dated and cataloged according to their form, material, and decoration. The ceramic sherds we found include many pieces with printed or hand-painted decoration, as well as a few maker's marks. Ceramics can provide insights into the domestic practices, diet, and social class of the people who owned them, as well as the networks of trade that connected them with ceramic manufacturers.

-For lithics (stone artifacts) we want to know what kind of tool it was or, in the case of the one chert flake we found, what kind of flake (there are multiple types of flakes, produced by various preparatory techniques). Stone artifacts are notoriously difficult to date but it may be possible to assign them to a broad time period based on their form or through their stratigraphic level or association with other artifacts.

-For bones, we may ask what animal it was, what part of the anatomy is represented, how it was butchered, and the age of the animal at the time of its death. The answers may provide insights into the diet and animal husbandry practices of the local population.