Dig Diary #11 March 2007

by Stefan Woehlke 

Mixing my PEG solution!

In 2004 a well was located just ten feet from George Washington’s Distillery. According to documentary sources it was built in 1798 in order to supplement the high demand for water created by both the Gristmill and Distillery. The excavation of this well in April and May of 2006 yielded a wealth of organic remains because the waterlogged environment aids the preservation of this material. Among these organic remains was a large amount of wood – both natural and worked.

Pine plank before conservation.

Mount Vernon's archaeologists are fortunate to work with Alexandria Conservation Services whose president, Lisa Young, is one of the premier archaeological conservators in the region, and she specializes in waterlogged archaeological artifacts.  Lisa was as excited as we were by the presence of so much organic material.  We are also fortunate to work closely with Justine McKnight, our archaeobotanical consultant, who identified the wood species in this project.  Beginning in February of 2007 working under Lisa's guidance, I began to clean and conserve nine samples that were selected because they were architectural fragments possessing worked elements. These samples were gently rinsed with water and a soft bristled brush daily for about two weeks in order to prepare them for an infusion treatment of Polyethylene Glycol (PEG). The purpose of the PEG treatment is to replace the waterlogged H2O molecules with the stable polyethelyne glycol molecules that bond to the cell walls of the wood so that it does not break down or collapse when the water is removed through slow or freeze drying. As the water evaporates out of the solution the wood will slowly be exposed to higher and higher PEG to water ratios, allowing the PEG to infuse the wood all the way to the core.

Beveled end of floor board with nail hole visible.

Before the samples were submerged in the PEG and water mixture, each piece was carefully traced, recording all marks on the wood. These included nail holes, beveling, cracks, excessive rotting, saw and cut marks, as well as unworked portions. I weighed each piece and performed a pin test where a straight pin was pushed into each sample in order to estimate the state of decay. These measurements were taken because different types of wood, as well as different amounts of decay require adjustments in the percentage of PEG required for conservation.

After all that, it was finally time to prepare my PEG mixture and start the actual conservation. This process was slightly abbreviated from the most preferred methods that calculate the best ratio of water to PEG based on specific gravity and state of decay of each individual sample. We used a 4:1 ratio, or 80% water and 20% PEG mixture. Lisa has found that this is a good average for similar pieces and she has conserved hundreds of waterlogged wood samples from Philadelphia. These nine samples are now resting in their solution.

From left to right: unworked cedar post; long worked pine post; short worked pine post.

In addition to the nine samples previously mentioned, there were three more fence posts, which were kept submerged in water, while conservation options were weighed. Two are prepared pine posts and one cedar log was not shaped into a post yet.  Lisa suggested that we could let them air dry in the lab and use dry silica to help prevent moisture build up while the wood dried slowly. These three pieces were cleaned thoroughly for a number of days in a row, and then notes were taken on the wood’s dimensions and state of decay. Tracings onto mylar paper were made so that there was a good record of the wood’s preconservation conditions. Dry Silica Gel-Crystals were then divided into pouches and distributed around the wood pieces as evenly as possible.

Daily checkups on the wood specimens revealed that mold was growing on one of the posts. I rotated it, trying to help it dry evenly, instead of having the bottom remain so moist. Lisa provided a few options to fight the mold. I decided to carefully brush ethanol on the mold in an attempt to kill it, and it seemed to take a rapid effect. Much to my surprise, after a long weekend the mold was back and in full force. I again gave it an ethanol treatment, and continued it regularly until the samples were air dried. This was after they started to visibly dry out, but the small pine post in the poorest condition suffered from a large amount of warping and cracking during this process. The well preserved pine post suffered from a little cracking and mold growth, but nothing too destructive, and the cedar post is doing best of all, and has maintained its good condition throughout the process except for a small amount of mold that was easily dealt with.

I’ll keep you posted on the trials and successes of the conservation process. I also plan to post pictures of the wood after it is conserved.

Dig Diary #10 November 2005

Eleanor simultaneously digs and supports her hometown baseball team (the new Washington Nationals).

We’ve been back out at the distillery site on a limited basis since the beginning of October. Digging in the fall in Virginia is an archaeologist’s dream – the temperature is perfect, no humidity, the leaves are changing, the sun isn’t too strong… Remind me I said this in February when I’m cold, muddy, and cranky! Our goal back out at the distillery is to conduct limited excavations in advance of the waterline construction that will begin at the modern millrace and end at the southeast corner of the building. You can see the square hole in the wall where the water will enter the building. The supports holding up the waterline nearest to the building’s corner will impact the historic soils and features.

Map of the distillery done in GIS. Our 5x10’ unit is located in the bottom, left hand corner of the site. Note the large ditch feature south of the foundation.

From previous excavations, we actually know that a large ditch feature runs parallel to the south wall of the distillery. We hypothesize that this feature represents an outflow ditch to carry water overflowing from the millrace down the hill to the creek.

North wall of the excavation unit with reconstructed distillery in the background. Dense, orange clay and brown loam fill layers are visible.

After removing about 2’ of fill (a clay layer dating after the 1930s and a brown loam layer dating to the 19th century), we came down on a line representing the fill of the millrace outflow. So far, we’ve exposed the feature in a 5x10’ area. We only have the southern edge of the ditch; the northern edge still lies buried under the fill. The fill of the millrace itself seems to be stratified into two major episodes – the upper, loamy, artifact-rich layer and the lower, sandy, clean layer.

Sample of artifacts excavated from upper layers of millrace outflow. Clockwise from the top left: painted pearlware; painted Chinese export porcelain; glass bottle; and brown stoneware.

In the upper fill of the millrace, we’ve found ceramics that indicate a 19th-century filling episode. We plan to explore this area with additional test units in the coming weeks. We believe that this excavation should provide enough of a buffer for the construction crew to complete their work without impacting any of the archaeological resources.

DIG DIARY #9 October 2005

Part of what’s fun about working at Mount Vernon is hearing from people who like George Washington, or have memories about their visit to Mount Vernon. This is one reason we added the American Mecca and Democratic Architecture pages to our website, to encourage folks to tell us how they’ve been influenced by Washington, or his home.

Casey Shive and his history project.

The other day we received a letter from Casey Shive, a high school student at Ritchie County High in Pullman, West Virginia. Mount Vernon is Casey’s grandmother’s favorite landmark, but he has not had a chance to visit. For history last year, Casey had to construct a project from the Revolutionary War era. While researching, Casey read about George Washington’s Distillery and he decided to recreate Washington’s still.

It took him about six weeks to fabricate the still, furnace and worm. The bricks for the furnace are roofing shingles; the copper still was an old tea kettle he found at a flea market. He used scrap wood to make the worm tub and “learned quite a bit about barrel making” in the process. The fire in the furnace is one of those bowls with fake fire they sell around Halloween. Casey reports that “the class enjoyed seeing the still as well as hearing about George Washington’s Distillery.”

He received a 97 on the project and he tells me that he enjoys history a lot, as well as computers. We sent Casey a book about Washington’s Mill and Distillery and invited him to visit the reconstructed distillery. If you’ve got a story, memory or question about Mount Vernon, please send them to us.