Uncategorized Archaeology, Big Bend Maritime Center, Canoes, conservation, Dugouts, Florida, Florida Public Archaeology Network, Gainesville, Lake Munson, Native American, Newnan Lake, Panacea, Preservation, Tallahassee 1 Comment
Have you ever seen an ancient wooden artifact on display at a museum and wondered how it was preserved in such great condition? I sure have! I have a compost pile at home and it doesn’t take long for wooden or other organic
material, to rot and turn into soil. It may seem strange that a wooden or organic object can last long enough in the ground for it to be uncovered by archaeologists hundreds or thousands of years later. Well, it turns out that it takes a very specific set of environmental circumstances for organic material to be preserved in the ground, and many times those conditions do not exist. And it may seem strange, but it is actually a wet environment that leads to good preservation! Organic materials, such as wood, are far more likely to survive the test of time if they are quickly buried in mud and muck. This creates an anaerobic environment, where a lack of oxygen prevents organisms that degrade wood (bacteria, worms, etc) from living and subsiding. As a result, the organic material is preserved until it is again exposed to oxygen. Within the last couple of years I have had the opportunity to see, first hand, how environmental conditions affect preservation of dugout canoes found in here in Florida.
You may recall a few years ago that a dugout canoe was recovered from Lake Munson in Tallahassee. The city had drawn down the water and a dugout was discovered lying at the bottom of the lake bed, only partially exposed. Archaeologists from various state organizations delicately recovered the dugout and brought it to the state conservation facility where it was properly cared for and conserved. After over a year of conservation it is now on display in the lobby of the R.A. Gray Building in downtown Tallahassee. This dugout is believed to be between 800 to 500 years old and was found in an excellent state of preservation. You can even see the tool marks were Native Americans carved out the wood to create the dugout! The state of preservation varied at different portions of this dugout, probably because different portions were exposed to differing amounts of oxygen throughout time. The higher edges are far more degraded than the lower sections and the hull because these would have been exposed to aerobic (oxygenated) conditions for longer periods of time. Overall though, the dugout was found in excellent condition. When the Lake Munson canoe was removed from the lake bottom care had to be taken by professional archaeologists and conservators to ensure that the wood did not dry out too quickly. After hundreds of years underwater, the material has reached equilibrium with its surrounding environment, and removing it from that environment can cause it to deteriorate to a point that it is destroyed if it is not done so carefully and correctly. If the wood were to dry out too rapidly it would cause it to shrink and crack. Wood is anisotropic, which means that it doesn’t expand or contract equally along its three dimensions. Evidence of this can be seen in many wooden objects that have been removed and stored incorrectly in what is called check cracking (it looks like lots of tic-tac-toes) and splitting.
During periods of drought many times partially exposed dugouts are found in lakes around the state. The most notable of this instance is of course, Newnan’s Lake near Gainesville. Here the largest concentration of wooden (both pine and cypress) dugout canoes in North America were recovered in 2000. They had become exposed due to extreme drought conditions. Frequent burial and reburial due to environmental conditions in a lake or other water body, can have a huge impact on the condition of the wooden object. In the event that a canoe is not entirely buried and lake levels fall due to drought, one can expect rapid deterioration of the wood as a result of it drying out too fast and exposure to the bleaching effects of ultra violet light from the sun.
Another concern with organic objects is storage. A dugout canoe was recently donated by the state to the Big Bend Maritime Museum in Panacea. Prior to its time at the state collections facility, this dugout had been found by a
private individual and was stored inappropriately on the ground outdoors for a number of years. As a result, it made the perfect home (and meal) for many different insects, including ants and termites. Pests are very problematic for organic archaeological collections, and care must be taken to ensure a collection is free from bugs. In many institutions, when an organic object is acquired –be it paper, ethnographic, wooden, etc – it is quarantined for at least 30 days. Proper storage and care of this particular dugout would have prevented the structural and surface issues that it has. Again, it goes back to the age old concept of context. If you do find a dugout, or any other artifact for that matter, it is best to leave it where it is and notify a professional archaeologist who will know how to best care for that particular object. The Big Bend Maritime Museum plans to have this dugout on exhibit and plans to include a panel discussing such preservation issues.
Typically a water-soluble wax is used to preserve extremely waterlogged wooden material. The idea is that through soaking the wax impregnates the cell walls that have been destroyed by water and degraded by bacteria, so that when the object is eventually dried out it retains its original shape. The Lake Munson canoe was not waterlogged to the extent that rendered this time-consuming procedure necessary. Instead, it was wrapped in plastic and allowed to dry very slowly in controlled conditions over the course of a year. The plastic functioned as a very basic humidity chamber that prevented any drastic change along any one of the three dimensions of the wood. As a result of this there are very little visible signs of checking on the surface of the wood. In order to achieve such wonderful preservation results it took over a year’s work by very knowledgeable professional conservators to monitor the progress of the Lake Munson canoe. Thanks to the work of professional conservators, who work behind the scenes the majority of the time, we have a great wealth of knowledge of our state’s history. If it was not for their careful efforts we would have only part of the story and only part of the artifact assemblage would have survived the test of time.