Some very interesting conclusions were included in the latest Archaeological Report of the Excavations at the Wistarburgh Site. The actual digging took place in April and November of 2001, but the report was just released in June, 2004. In all, there were over 100 shovel test holes, one ten foot square trench in the field, and a three foot by six foot trench near the house. The report included many artifacts found on the surface of the target field and across Commissioners Pike. In addition, many bottle closures and bottle bases previously found on the surface were studied. Some interesting conclusions follow.
The most prolific artifact found at the site of the Wistarburgh Glass Works is flat glass or window glass. Over 40 % of all artifacts retained from the various excavations, shovel tests or trench, were flat or window glass. The colors ranged from blue green, to pale green, aqua to light aqua as listed in the Archaeological report by Hunter Research Inc. of June 2004. Not listed was any flat glass in undisputable clear glass.
The importance of flat glass to the Wistarburgh Glass Works can be seen in the specific stipulation of the Casper Wistar Will. Richard Wistar, son of Casper, was given the Glass Factory, but Richard was required to supply his brother Casper, who was residing in New York City, with an amount of glass from the factory, which included some bottles and much flat glass. The Will stated that Richard was to supply 900 boxes of several sizes of flat glass, and 10 dozen bottles every year. The boxes of flat glass contained about 60 panes of glass. A box of glass panes of this type sold for $7.00, or $0.12 per pane in 1797. In 1752, the price may have been a little lower, but at the 1797 prices, Richard had to supply flat glass panes valued at nearly $6300, every year. The total value of the bottles in the Will requirement was about $5.00 per year. So, Casper Wistar placed much more importance on the flat glass business than he did on the bottle business. To make an equitable split of his possessions, he relied on the flat glass, which Casper Jr. was able to sell in New York. While this volume of glass to be shipped to Casper Jr. seems like a lot, it couldnt have presented much of a burden on Richard and the Glass Factory. If this amount of glass was one eighth of the yearly production, then Richards gross income may have been $44,000 per annum for just flat glass. Although the plant operation, raw materials, and wages would be deducted, this is still a good sum for 1753 It is becoming very clear, with the help of the Archaeological investigations and reports, that the Wistarburgh Glass Factory was very successful due to the production of flat glass, and not so much the bottles and occasion tableware or whimsy items which are so highly desired.
The June 2004 Report contains good information about bottle openings and bases. This includes the common chestnut type bottle with the rolled lip. These bottles were found in a medium aqua to a medium green, but no blue The size may be less than a quart, but not quite as small as a pint, to the larger two quart size similar to the Heston bottles. There was some variation to the rolled tops, as seen at the top of page 4-28 of the report. There was also some variation to the base of the chestnuts. Some had a rather conical pontil, while others had a small push-up with a ¾ to 1 inch pontil scar. Both types of bases have been found as artifacts and as examples, although the conical pontils are usually on the larger chestnuts.
Also studied in this report were the many so called black glass string lips. These included those found during this investigation, along with those previously found. A few of these tops are shown on page 4-28 of the report. The most significant being the left hand example on the bottom row.
This is a malformed, dark olive green, tooled string lip. This bottle top was discarded while still hot, showing that it was manufactured on site. In chapter four, the report explains the logic of black glass being made at the Wistarburgh Glass Factory. Earlier researchers have assumed that any black glass found at the site, was brought in as cullet. They also assumed that it was not possible to make black glass with wood as a fuel. Chapter four makes the case that black glass actually was made at the Wistarburgh Glass Works. This is a gigantic change in the view of products from the factory. Black glass mallets have not previously been accepted as products of the Wistarburgh Glass Works.
On page 4-17 of the report is a section on Glass Items of Interest. These items have the most interest for collectors. On page 4-19 are pictured a few of these items, including a triple knop knob, or handle; twisted sugar bowl handle with rigaree; hollow stopper; pieces of a broken ribbed, pattern molded pocket bottle; and several different size tubes from scientific ware or whimsical horns.
The glass colors found were pale green, various shades of aqua, dark green (black), amber, clear/uncolored, amethyst and blue. These colors were consistent with previous excavations at the site. Mentioned later will be an analytical report by J. Victor Owen, which found that some blue glass contains between 3 and 17 % lead.
There were also many rolled lip or folded lip artifacts from bowls, in aqua and clear glass found, both in the excavations and on the surface. The tableware and whimsical items were not part of the regular production of the glass factory. These items were made after hours or on Saturday. Glass factories have always allowed the glass workers to make items for themselves, sometimes to use at home, or to give to a special friend. There apparently existed this same custom at the Wistarburgh Glass Factory. These non-production items draw a lot of interest in the world of collectors. It has only been recently that enough artifacts have been unearthed to establish that many items attributed to later glass factories could have been made at Wistarburgh.
There have been a few items found recently that have been authenticated as being made at the Wistarburgh Glass Works. This authentication sometimes comes with written documentation that has accompanied the item through its 250 year life, or possibly by family authentication, which is verbal, but has been handed down through many generations of Wistar family.
J. Victor Owen
Another method used recently has been a destructive chemical and instrument analyses using an electron microprobe. This requires a very small piece of an item to be submitted for analyses. This piece is usually obtained from the pontil scar. This destructive analyses is much more sensitive and accurate than the previously used non-destructive x-ray fluorescence analyses. J. Victor Owen reports his findings, in the Canadian Journal of Earth Science #41, June, 2004, from 15 glass factories in New Jersey and Connecticut. This report Geochemistry of Wistarburgh Glass indicates that it is possible, with this analytical process, to distinguish glass of Wistarburgh from other 18th and 19th century glass factories in Southern New Jersey. Although the access to this analytical procedure may be limited, this report acknowledges identification is possible