Monday, August 23, 2021

Shining a Light on Radioactive Uranium Glass

This week’s blog focus is uranium glass (also called Vaseline or canary glass). Although seemingly non-descript under incandescent lighting, these objects fluoresce brilliantly when viewed under an ultraviolet black light. The glow produced by these objects is a result of the colorant used in the vessels – uranium. Uranium glass was widely popular and was produced by several Pennsylvania glass manufacturers. While using uranium glass for food consumption is not recommended, they usually pose little danger to people.

Photo by Melanie Mayhew (private collection)

The hidden properties of uranium glass are revealed under a black light.

Uranium was formally discovered over 220 years ago by German chemist Martin Klaproth. Klaproth named this element “uran” after the planet Uranus. As with the discovery of other brightly colored compounds and elements, uranium soon became a popular pigment. The first documented use as a glass colorant was recorded in 1817 (Lole 1995). Its popularity as a colorant in Europe later spread to the United States and Japan. Natural uranium was used to color glass, enamels, and ceramic glazes until the 1940s when the onset of World War II resulted in a production gap of uranium-containing housewares. Depleted uranium was made available for use beginning in 1959. Although uranium use as a colorant has decreased dramatically in recent decades, some contemporary objects claiming to contain uranium can still be found for sale online.

Photo by Andrew Silver, USGS, Public domain, via Wikimedia Commons

The natural yellow to green color of uranium ore led to the widespread use of this material as a colorant.

Uranium glass is most frequently associated with yellow to yellow-green colors, but fluorescent objects were later made in a range of colors. There is a lack of awareness around the widespread use of uranium colorants (Strahan 2001), possibly because without a black light or specialized knowledge of uranium colorants, identification by archaeologists can be easily missed. Archaeologists use several observational methods to identify and classify artifacts, and a UV light is a useful tool to assist with the identification of objects containing radioactive colorants. The Corning Museum of Glass identifies several other components used in glass manufacture that may also fluoresce, such as antimony (light pink or pink-orange), manganese (yellow), and glass with a high lead content (bluish white).

Photos by Wombat1138, Public Domain via Wikimedia Commons

Glass objects containing radioactive material have been made in a range of colors, making their identification more difficult.

Pennsylvania's rich resources, including sand, coal, and flint, contributed to its importance as a glass manufacturer. By the time of the Civil War, Pittsburgh, Pennsylvania was the premier city for glassworks in the United States. Many glass manufacturers in Pittsburgh produced a range of uranium glass housewares to satisfy consumer demand at the turn of the 20th century.

For those with a fondness for these objects, the Environmental Protection Agency (EPA) indicates there is usually little health risk involved with keeping antiques containing radioactive materials, if they are in good condition. Moreover, an additional source indicates little health risk unless objects are stored in a small area, are used to store and consume large quantities of acidic or alkaline foods, or if the object must be drilled for conservation work thus creating a dust from the removed material (Strahan 2001).

We hope you have enjoyed this blog on the hidden properties of uranium glass. We invite you to explore related objects by searching for the popular term “Vaseline glass” in the Pennsylvania Historical and Museum Commission’s online collections database.

Argonne National Laboratory

N.D.       Uranium Quick Facts. Depleted UF6 Guide., accessed August 10, 2021.

Corning Museum of Glass

N.D.       Conservation Laboratory. Conservation., accessed August 10, 2021.

Environmental Protection Agency (EPA)

N.D.       Radioactivity in Antiques. Radtown., accessed August 10, 2021

Heinz History Center

N.D.       Glass: Shattering Notions. Exhibits., accessed August 10, 2021

Lole, F. Peter

1995      Uranium Glass in 1817- A Pre-Riedel Record. Journal of Glass Studies 37:139-140.

Strahan, Donna

2001      Uranium in Glass, Glazes and Enamels: History, Identification and Handling. Studies in Conservation 46(3):181-195

For more information, visit or the Hall of Anthropology and Archaeology at The State Museum of Pennsylvania .

Tuesday, August 3, 2021

Henry William Stiegel - Manheim and Stiegel-type Glass

This week we are taking a departure from ceramics and pottery to look at some interesting glass that was found at Fort Hunter during the 2020 field season. Though only a few small fragments were recovered, this type of glass has an interesting history in Pennsylvania. Hand painted enameled pieces such as these found in the United States are known as Stiegel-type glass due to their association with ironmaster and glassmaker, Henry William Stiegel.

Stiegel-type enamel painted tumbler from two views. Photo from the Community and Domestic Life Collection, The State Museum of Pennsylvania.

Henry William Stiegel was a German born immigrant who arrived in Philadelphia in 1750 with his mother and brother. Here he worked for two years as a clerk for ship merchants, Alexander and Charles Stedman, before taking work with ironmaster Jacob Huber, in Lancaster County. Within the year, Stiegel married Huber’s daughter Elizabeth who passed away shortly after the birth of their second daughter in 1758. Also in 1758, Stiegel along with his partners the Stedman’s, bought out Huber, becoming the new owners of the iron furnace, which was renamed Elizabeth Furnace after Stiegel’s late wife. Shortly after, the partners purchased an additional furnace near Lancaster County, named Charming Forge, to help expand Stiegel’s ironworks. 

Cast-iron right-side stove plate made by Jacob Huber at Elizabeth Furnace. Photo from the Ephrata Cloister Collection, The Pennsylvania Historic Museum Commission.

By this time, Stiegel had become a prominent member of the community and Lutheran Church and was well known as a great ironmaster, best known for his cast iron stoves. In 1762 Stiegel with the help of the Stedman brothers planned the town of Manheim. It was here that Stiegel built his mansion and in 1764 opened his newly built “glasshouse”, which the town was built around. Later called the American Flint Glass manufactory, Stiegel continued to expand on the glasshouse, hiring highly skilled workers from Europe’s prominent glassmaking centers. Beginning with window glass and utilitarian bottles, Stiegel’s glassworks later produced colored glass pitchers, wine glasses, dishes and bowls as well as scientific items. The American Flint Glass Manufactory also produced decorated pieces, some etched and others hand painted enameled in the traditional German red, yellow and blue motifs. Due to the lack of makers marks or signatures on the pieces produced by Stiegel’s glassworks and the similarity in design to European pieces of the time, it is near impossible to know for sure whether unmarked pieces were made here in Pennsylvania by Stiegel’s company or if they were imported from Europe, as many were. 

Stiegel-type eight-sided panel bottle from Conestoga Indian Town site, 36La52. Photo from the Section of Archaeology, The State Museum of Pennsylvania.

Eventually Stiegel became the sole owner of Manheim. He built schools to educate the children of his employees, donated the land for the Manheim Lutheran Church, and supported a musical band in Manheim. Stiegel has often been referred to as Baron Von Stiegel, the founder of Manheim, Pennsylvania. Unfortunately, just before the Revolutionary War, Stiegel found himself in financial collapse and unable to pay his debts. In 1775 the glassworks ceased production and Stiegel had to sell off all his land. After spending some time in debtors’ prison, Stiegel came to rely on family for support and did some work as a bookkeeper and a teacher. Stiegel died in 1785 and since the glassworks had closed, Manheim was left to struggle as a small town with a low population and in 1838 was incorporated as a borough by the Commonwealth. Though Manheim is not the great metropolis Stiegel had planned for, he did build the town leaving a lasting impression on Manheim and iron and glassworks in the United States and Pennsylvania.

As mentioned above, the glassware produced by Stiegel’s company was not marked in any way to indicate when or who produced it. With new technologies, such as laser ablation, it may be possible to identify trace elements within the glass made by Stiegel to distinguish it from those of European origin, but limited research has been done at this time. Since there has been limited testing done with laser ablation and other new technologies in relation to glass identification it is currently unknown if glassware in this enameled hand painted style was produced by Stiegel or imported from Europe and is therefore called Stiegel-type glass. These fragments found at Fort Hunter are a great example of Stiegel-type glass that is found on archaeological sites today.

Stiegel-type glass found at Fort Hunter, 36Da159. Photo from the Section of Archaeology, The State Museum of Pennsylvania.

We hope you have enjoyed this brief history of Henry William Stiegel, Stiegel-type glass and Manheim, Pennsylvania and how they are related. It is interesting how even the small artifacts can evoke the rich history of individuals and their mark on the world we live in. We invite you to explore additional examples of Stiegel-type glass and other artifacts via Pennsylvania Historical and Museum Commission’s online collections database.



Corning Museum of Glass, Glass of H.W. Stiegel: Accessed July 19, 2021.

Greenough, John D. and J. Victor Owen

2018      A Laser Ablation Study of Glass Samples from Three Eighteenth-Century Germanic-American Glassworks: Amelung, Stiegel, and Wistarburgh. In The Journal of the Society for Industrial Archaeology, pp. 5-24. Society for Industrial Archaeology, Houghton, MI.

Hume, Ivor Noel                                                                                              

1969      A Guide to Artifacts of Colonial America. University of Pennsylvania Press, Philadelphia (reprint)

 Manheim Historical Society, Revealing Manheim’s colorful past: Accessed July 19, 2021.

The Hershey Story, Henry William Stiegel – Ironmaster and Glass Maker: Accessed July 19, 2021.



 For more information, visit or the Hall of Anthropology and Archaeology at The State Museum of Pennsylvania .