Welsback Company Lit-Up Nineteenth-Century America and Leaving Behind New Jersey’s Biggest Radioactive Superfund Cleanup Site

Note: All items pictured on this website are in Frank W. Reiser's personal collection. Please contact if you wish to discuss exhibiting the collection at your institution or need additional information about the topic.
A section from a Welsbach mantle shows the weave of its thorium-impregnated fabric. The slide holds Welsbach mantles are the brightly glowing element that makes the bright light of a gas lamp.  When cool, they look like a small net-like bag covering the flame. The mantle cloth is infused with metal salts, primarily thorium nitrate, a process developed by Carl Auer von Welsbach (1858 – 1929), an Austrian chemist, in 1884. When the treated cloth is heated, it glows brightly, providing a strong light. Once burned, the mantle becomes fragile and collapses into a white powder if touched or shaken, but if handled carefully, it can be used repeatedly. Thorium is a radioactive element, but it is not particularly dangerous to the general public since it emits low-energy alpha radiation. Its slow decay rate, a half-life of about 14 billion years, sounds impressively radioactive, but the type of radiation it emits can be blocked by a sheet of aluminum foil. Nevertheless, it should not be ingested or inhaled. 

The Welsbach factory, located in Glouster, New Jersey, was not only a manufacturer of mantles for gas lighting but also a refiner of thorium. The raw material, monazite sand, was mined in South Carolina and processed by Welsbach in rotating furnaces to extract thorium. Welsbach was also a supplier of thorium to other gas-light mantle manufacturing companies. The residuals left over after thorium extraction, along with the factory’s other mantle manufacturing waste, were dumped over several acres surrounding the Welsbach factory. (Cleary 2020)

Welsbach thorium infused mantle fabric before burning off the cotton.
Walsbach Mantle. Woven thorium nitrate and cesium oxide impregnated cotton thread. The specimen has yet to be burned off, a process that will carbonize the cotton, leaving a skeleton framework of mineral salts that glow brightly when heated. prior to using in a lamp. 100x Stacked from 50 images, top stage illumination.

 Before the advent of electric lighting, gas flames equipped with Welsbach mantles flooded city streets with light of intensity never before seen.
The best mantles were made using Ramie. It is a natural fiber obtained from the stem of the ramie plant Boehmeria nivea, also known as China grass or rhea. These fibers are recognized for their strength, sheen, and exceptional ability to withstand heat compared to other natural fibers. However, due to their stiffness and brittleness, they present challenges during processing. As a result, cotton was used instead to speed up assembly lines. 

The manufacture of thorium mantles involves a series of meticulous hand operations that have remained essentially unchanged despite the steep reduction in demand over time. Coleman has taken over mantle manufacturing but has eliminated radioactive components. An absorbent thread that is knitted into a tubular fabric known as a stocking. This fabric is then soaked in a solution composed of thorium nitrate with a small addition of cerium nitrate to enhance brightness and salts of aluminum and beryllium to strengthen the mantle. After drying, the fabric is briefly ignited. This ignition burns away the fabric, leaving behind a delicate, self-supporting skeleton made of thorium and cerium nitrates. Called “hard” mantles, they were very fragile and had to be coated with Collodian before being shipped and installed in gas lights. They were attached to a base that enabled them to be installed without touching the mantle material itself.  In some variations, a supporting wire frame was also attached to the base for additional protection. Hard mantles were commonly used in both domestic and street lighting from the late 19th to the early 20th century.

A set of three postcards issued by Welsbach at the turn of the century. 

A series of postcards was issued by the Welsback company to advertise the manufacture of their mantles. These postcards are of the early design introduced by the Post Office in 1860 and did not have a divided back to allow for both a message and an address. Information from the sender had to be crowded in the margins on the picture side of the postcard. The Wesbach postcards were mainly used by the company’s sales personnel.  The first divided-back postcards were not authorized by Congress until 1906,

Welsboch mantles superfund site
Welsbach thorium nitrite purification
Welsbach rotating furnaces for thorium production
The ore was mined in South Carolina and processed in rotating furnaces to extract the element, which Welsbach used and supplied to other gas-light mantle manufacturing companies.
Welsbach mantle production line.
Inspecting and trimming mantles before “burning off” to make the hard mantles used during the turn of the century.

 

 

Welsbach Inverted Mantle
Welsbach Inverted Mantle. After the cotton framework was burned off, a fragile mesh-like dome remained. It was attached to a porcelain base and coated with collodion to support its installation in gas lamps.
Lindsay mantle and Reliable mantle were two competitors with Welsbach
Lindsay and Reliable were two mantle competitors with Welsbach.

 

Lewis Woolman (1841 – 1903), an amateur geologist interested in microscopy, was employed by New Jersey in 1889 to study mineral layers in water well drilling. Alongside his professional work, he independently examined specimens from various sources in nearby states. Most of Woolman’s microscope slides, created during this period, focused on these geological samples. There is no evidence that Woolman sold his slides, indicating they were likely made for personal study or shared within his professional network. (Stevenson 2016, Available at: http://microscopist.net/WoolmanL.html)

How to footnote this page:   Reiser, Frank W. (2024). Welsback Company Lit-Up Nineteenth-Century America. Available at: https://antiqueslides.net/welsback-mantles-superfund/

References

Albert, Roy E. (1966). Thorium: Its Industrial Hygiene Aspects. Academic Press, NY

Cleary, William. (2020 )The Cleanup of Gloucester City’s Superfund Sites Continues: $384 Million Spent So Far. Gloucester City News, NJ. January 26.