Technical Study and Treatment of an Early Battery Assemblage

May 08, 2023

The evolution of batteries parallels our advances in both chemistry and materials science. They have served as a portable power source allowing continuous innovations in aerospace technology and have been utilized since the origins of aviation. One example of this evolution is the set of batteries seen below. These are part of the Museum's Samuel Langley laboratory experiments, providing power to Langley's later aviation and scientific experiments.

Langley lived from 1834 to 1906 and was an aviation pioneer. He became known for his rubber-band powered models and aerodromes and competed against the Wright brothers in the race to develop the first functional flying machine. Langley also served as the third Secretary of the Smithsonian Institution and built some of his early experimental aircraft behind the Smithsonian Castle.

The batteries pictured provided around 1.4 volts and 12-16 amperes, which is much improved from the earlier forms of this type of battery cell. These particular batteries were manufactured by the Samson Battery Company/Electric Goods Manufacturing Company in Boston, Massachusetts, around the end of the 19th century. Sampson jar batteries, such as these, were used to power doorbells, telephones, early electric lighting, and small electronics. They represent a period when batteries were undergoing a technical revolution and becoming more common in American lives.

The series of five battery cells are composed of rectangular aqua blue glass jars with lids. On the top of each lid is a central positive terminal and a negative terminal off to one side. Hanging from the lids are zinc rods surrounded by carbon-manganese cylinders. Each cell would have been wired to the other in series, thus forming a "battery." When in use, each jar would have been filled with sal-ammoniac (ammonium chloride) and water that would act as the electrolyte solution.

These batteries suffered from extensive corrosion on the zinc rod that forms the positive terminal. The outward force of the corrosion broke several of the ceramic insulators where the rod meets the lid. Additionally, the loose zinc corrosion product had spread across the surface of the lids (as seen in the image above). The copper and ferrous components of the terminals and wires had also developed corrosion.

Analytical techniques were used to gain a deeper understanding of the various components before conservation treatments took place.

Ultraviolet (UV) photography is used to help identify surface features not detectible under visible light and to characterize materials.

The UV light showed two particularly interesting features: a bright fluorescence on top of the lid, and the green hue of the glass.

It is typical for zinc corrosion to fluoresce a light blue-green. The UV induced fluorescent green hue of the glass jar was likely caused by an additive to the glass. One theory is that the fluorescence could be caused by the use of uranium in glass. This was a common glass production practice between the 1880s and 1920s.3 However, this theory was disproven by both the XRF analysis (see section below) and the testing of glass for radiation with a Geiger counter. Another explanation for this eerie glow is the addition of manganese to the glass. This has been a practice for centuries to help remove the dark green color of glass caused by iron impurities undergoing an oxidation-reduction (redox) reaction during production.

To confirm this theory, we used X-ray Fluorescence (XRF) — a technique used to non-destructively identify inorganic elements within a material— on several components of battery "A". The glass jar showed copper and manganese elements, which may contribute to the aqua blue color of the glass. The presence of manganese is consistent with the green fluoresce seen in the UV photographs.

We also collected and analyzed loose pieces of material using Fourier-Transform Infrared Spectroscopy (FTIR). This technique creates an infrared spectrum of the material's absorption. We analyzed a sample of waxy material found inside the jar and on the top of the internal components and found it to be paraffin wax. This is consistent with a report found in the 1901 edition of "Electric Gas Lighting."2 The paraffin wax was used as a protective layer on the top of the jar and lid to repel any of the electrolyte solution that may have spilled during use.

We also conducted analysis on a curious textile addition found wrapped around the copper wires between each cell and we determined it was silk. While silk may seem to be an odd choice as an insulating material for copper wire, 19th century English scientist Michael Faraday was a proponent of this method with his experiments involving galvanometers.1 The elasticity of the silk allowed it to move with the wire when it was bent without exposing the underlying bare metal. This sort of textile wrapping is an early version of the plastic wire coverings we use today.

The goal of the treatment was to retain and preserve any historical information and all original materials within the batteries. This was balanced with the need to protect and stabilize areas of deterioration. Battery treatments can be difficult as the inherent vice of the materials can make it difficult to retain certain components without compromising others.

The first step in the treatment included carefully removing all the loose zinc corrosion product from the lids. This was completed with soft brushes and light vacuum suction. The outsides of the glass jars were cleaned with cotton swabs dampened with deionized water. This was carefully undertaken so the paraffin wax on the shoulders of the jars was not disturbed.

While the exterior of the glass began to look less dusty and more transparent after cleaning, the interior had a mix of dust and deposits of sal ammoniac on all four sides. We tipped the sal ammoniac crystals out of each jar so that the internal sides of the jar could be cleaned in the same way as the exterior. This greatly improved the optical clarity of the glass. We then removed foreign debris from the sal ammoniac before placing it back into the jar. After making clear inserts from thin mylar, we placed them between the bottom of the jars and the crystals to protect the glass from the acidic nature of the sal ammoniac and prevent the development of glass disease.

After cleaning the glass, we treated the zinc electrode and positive terminal for corrosion, removing the unstable corrosion from the zinc, passivating any exposed metal surface using a mild acid, and giving the surface a clear protective coating. We then addressed the corrosion of the exposed copper wire, mechanically reducing it and coating it with the same protective layer. This layer helps to minimize the risk of further corrosion developing.

The goal of this conservation treatment was twofold: to stabilize the batteries for storage and to enhance the curatorial record with accurate material characterizations. With the reduction of the zinc corrosion and a low relative humidity environment, further corrosion development is unlikely. Similarly, the separation of the sal ammoniac electrolyte from the glass jar will assist in keeping both elements stable into the future.

Sources

1. Mills, A. 2004. The Early History of Insulated Copper Wire. Annals of Science, 61:4, 453-467.2. Schneider, N., 1901. Electric Gas Lighting. 1st ed. New York: Spon & Chamberlain.3. Emery, K., 2021. Gunson's Glowing Glass: History and Archaeology of Uranium Glass. [Blog] Michigan State University, Available at: <https://spartanideas.msu.edu/2016/03/17/gunsons-glowing-glass-history-a…; [Accessed 19 October 2021].

Meredith Sweeney was the Engen Conservation Fellow from 2019-2021. This blog was written as a component of her research into the care of historic batteries.