Soil Chemistry Explains Crumbling Ceramic Sherds
Julie:"While excavating out at the Market Master’s House site, we have noticed the very poor preservation of the ceramic artifacts. Many of the 18th and early 19th century ceramic fragments flake apart in layers as they are removed from their context. We suspected the poor preservation may be a result of the alkaline soil. This morning I stopped at the local hardware store and picked up 4 pH soil test kits for $1.50. I tested three strata in Test Unit 6 and found that the soil pH was very alkaline; the only neutral stratum was the 19th century layer that was filled with ash, coal, and artifacts. Based on our soil test, we found that the poor preservation of our 18th century ceramics was the result of the high alkalinity of the soil. Although this pH level is not good for the preservation of ceramic, glazes, lead, glass and fabrics, the alkaline soil seems less destructive to bone, lithics, shell, plaster, iron, and copper-alloy artifacts. "
Here is an interesting resource that desribes the effects of different soils on the preservation of artifacts:
The Discoveries of the Week Mike:"It was our second to last day at the site today. We finished all but one of the four test units we set out to complete this week. Our last week of fieldwork left us with some interesting finds. Postholes popped up in the bases of several units around the house, up to three feet below the surface. This suggests several things. First of all, the historic living surface of the Market Master’s House is much lower than the present surface level. A careful examination of our artifacts and fieldnotes will indicate to us, in coming months, how well preserved these early historic strata are. It also suggests that the historic landscape around the house was crowded with architectural features such as fences, awnings, and smaller impermanent wooden buildings. I now see the lone solid frame of the Market Master’s House differently, imagining it surrounded not by grassy lawn and gardens, but by a very different landscape of dense domestic, industrial, commercial and agricultural activities and their respective constructions.
Another interesting discovery made this week resulted from the shovel test pits we excavated below the asphalt of Market Lane, to the north of the house. The recovery of deeply buried artifacts from the 18th and 19th centuries suggests that some intact resources from that part of Lot 37 survive below the blacktop. All this suggests that, despite the long hours of work spent out at the Market Master’s House and the Magruder House, much remains to be learned about these resources."
Stay tuned for more at this blogsite as we report on the washing and analyzing of artifacts and the results of the architectural and deed research that is being conducted of the sites. We’ll also announce public events of the Bladensburg Archaeology Project and other local organizations, and report on what else is happening in archaeology around the region. The University of Maryland team will begin a small excavation at the Bostwick House starting Friday.
Here are some photos of the day including some of the delicious celebratory banana cream pie we ate from Clement’s in Bladensburg: