Introduction
Magnetic Fractioning, since its development by Henry Unglik in the 1980’s, has been used to determine percentages of microscopic metal fragments. The goal of this website is to relate the initial findings during the Spring 2002 investigation of the blacksmith shop at the Van Winkle Site (a late nineteenth early twentieth century sawmill/grist mill complex in Northwest Arkansas) in an effort to determine the placement of the anvil relative to an identified forge feature. Also, the process is presented in an easy to follow (and, hopefully, equally easy to duplicate) step-by-step description.
Location & Brief History
Van Hollow is located approximately 15miles east of Rogers, Arkansas in the Hobbs State Park - Conservation Area. Highway 12 and its embankment cuts through the site (obscuring at least one homestead) and the northern portion of the site has been inundated by the creation of Beaver Lake. The mill owned by Peter Van Winkle, and the surrounding community of worker, occupies a unique role in the history of Arkansas. Lumber produced at the mill was used extensively for late 19th century construction across northwest Arkansas (including Old Main at the University of Arkansas). The remains of the mill and other elements of the 19th century community are co-managed by Arkansas State Parks and the US Army Corps of Engineers. The Arkansas Archaeological Survey has conducted ongoing excavations at the park since 1997.
Principles & Theory
This technique has a single purpose, to determine the locations of various metal working regions within a single area. Magnetic fractioning seeks to determine the percentage of hammer scale and iron shavings present in soil samples. Hammer scale is simply the scatterings that result when a hammer strikes a piece of molten iron (the single most recognizable activity of any blacksmith or farrier). Iron shavings result during the finishing process of metal working when the blacksmith or farrier uses a file to shape the steel. These two types of residues are quite small (samples are often microscopic). The process of using the percentages to understand which parts of the shop were used for metalworking as opposed to other activities (such as horseshoeing, commerce, eating, etc.) is a fairly straightforward process. The higher the percentage of hammer scale and iron shavings in a sample, the higher the likelihood of metal working in the area of that sample.
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| Hammerscale | File |
Techniques
The physical source for sampling hammer scale and the iron shavings comes from soil samples taken from a site. In the case of the blacksmith shop, samples were collected across a 10 by 10 meter section that is believed to contain the shop. This area definition is based on the previous examination of Van Hollow during 2001 conducted by Jamie Brandon, James Davidson, and Brynn Berry. This examination identified the location of what was believed to be a forge, a conclusion supported by excavations that same year. This discovery, combined with remote sensing data obtained by Jamie Lockhart from the Arkansas Archaeological Survey, defined what is believed to be the boundaries of the shop.
The first step was to secure a series of soil samples from the site. Traditionally, this has meant obtaining samples after a site has been completely excavated down to the occupation level. This collection strategy at Van Hollow was modified due to the fact that a full-scale excavation has not yet occurred at the blacksmith shop. At Van Hollow, soil was collected from a column sample, each column was dug to approximately 30 cm (below the occupation level), and a soil sample was collected from the entire column. This is justified by the discovery of a gravel lens located a few centimeters throughout the site below any occupation levels (as shown from subsequent excavations). The affect this had on determining magnetic fractioning percentages was to lower the percentage, since the inclusion of soils above the occupation level were also incorporated within each sample. However, as will be shown below, the reduction of percentages has not stopped some clear work zones from appearing once the percentages were mapped across the site.
Collecting Samples
Samples-a-Plenty! (27 in total)
The collection of samples from a staggered series was believed to give the clearest and most unbiased representation from across the site. In the case of this shop, we took samples from columns spaced 1.5 meters apart and rows 1 meter apart, and for the purpose of control samples two samples were taken 2 full meters outside the defined collection area (samples A-3 and A-5).
Grid Point Locations
The laboratory work consisted of five phases.
Phase 1 involved screening the samples through two decreasingly sized screens (.5-inch followed by a .25-inch screening) to remove the largest rocks and plant matter.
Phase 2 consisted of the samples being dried in an oven for 8 hours at 100 degrees Fahrenheit.
Phase 3 was a third screening through a .125-inch screen to remove all remaining pebbles.
Phase 4 involved weighing and mixing each sample in water with a magnetic stirring bar. The first step is to weigh each soil sample and the clean stirring bar, and place them inside a cylinder with water. Then, each sample is mixed for 1 hour, and the magnetic stirring bar is removed and weighed, which now has the hammer scale and iron shavings attached to it. This phase provide the raw data used during the fifth and final phase.
Phase 5 uses the data obtained in the previous phase to calculate the percentages of magnetic fractioning of each sample. The formula used is:
(magnetic bar after stirring - magnetic bar before stirring)/soil sample weight * 100
This provides a simple percentage that can then be mapped across the site.
Findings
Below are two maps that show the results of overlaying the samples on the
map of the site. The second map has been overlaid on the remote sensing data
collected by Jamie Lockhart. Three major zones have been defined by the magnetic
fractioning percentages. Zone 1 is defined as the regions most likely being used
for heavy metal working, the region to the west of the forge (represented by the
blue square and black area in the remote sensing that represents no data, we
were unable to collect remote sensing data here due to previous excavations) is
exactly were one would expect to find the anvil, and subsequently the largest
percentages of magnetic fraction. Traditionally, the anvil would have been
situated within a step or two of the forge, and the sample D-6 (which provided
the largest sample percentage by far of the entire shop) is in such a position.
Excavations in this area would most likely turn up the stand of an anvil
(usually taking the form of a tree stump), but probably would turn up relatively
few large artifacts as this area would not have been used for storage. Zone 2 is
defined as regions were some metalworking took place, these zones represent the
possible locations of workbenches, were the blacksmith would have finished
working pieces of steel. Zone 3 represents areas that had little to no
metalworking, and most likely represent storage or commerce areas. Blacksmith
shops have a long tradition of being meeting places for community, and in the
cold winters of northwest
| Samples and Zones | Samples and Zones with Remote Sensing |
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The region excavated during Spring 2002, represented by the red rectangle, helps to support these zones. The artifacts recovered from this region are mostly large, finished industrial artifacts. These include horse and mule shoes, a large industrial crank, and horse and buggy parts. Column B may in fact represent the approximate western wall of the shop. This is clearly shown by the excavations during 2002, see photo below.
Conclusions
The use of magnetic fractioning at the Van Hollow Blacksmith Shop has clearly defined three different types of zones related to metalworking that occurred at the site. These three zones have been partially substantiated by excavations conducted during 2001 and 2002. I suggest that further excavations would continue to illuminate these zones, and that a full series of soil samples taken at 1 or .5 meter intervals from the occupation level would clearly define work spaces within the shop itself. Samples taken from the occupation level would allow the creation of a detailed map of specific features, such as the forge, location of bellows to power the forge, and fuel storage area. These archaeologically verifiable features could then be combined with magnetic fraction percentages to illustrate the inner arrangement of the shop, as it would have been over 100 years ago, an illustration that would prove very useful for the construction of an interpretive representation of the shop for the future.
Bibliography
Light, J. D.,
and Unglik, H. 1984 A Frontier Trade Blacksmith Shop: 1762-1812. Studies
in Archaeology, Architecture, and History. National Historic Parks and Sites
Branch, Parks