Research teams have developed a new approach to identifying the chemical composition of preservation fluids in historic jars without opening them.

The teams were from the Science and Technology Facilities Council (STFC), Natural History Museum and Agilent Technologies. The study was published in ACS Omega on 21 February 2025.

The role of historical specimens and artifacts cannot be overstated. They serve as tangible links to our ancestors, offering a wealth of knowledge and insights into our past.

These items collected throughout our history are invaluable to education and our cultural heritage, enlightening us on past civilizations, biodiversity and climates that help inform our current scientific understanding.

Non-invasive methods

This analytical capability is critically important in the curation of historical fluid specimens.

In some cases, these originate from Victorian times, where the composition of fluids could be poorly documented, or the specimen has lost one or more of its components by evaporation due to an imperfect seal.

The characterization of these fluids poses significant challenges as non-invasive methods are preferred to avoid opening jars and compromising specimens.

SORS

This proof-of-concept study investigates the feasibility of using a handheld Spatially Offset Raman Spectroscopy (SORS) device to determine the chemical composition of preservation fluids through their original glass containers.

SORS performs chemical analysis by shining a laser light into a container and inspecting the changes in wavelength that occur when the light is reflected.

These changes indicate the presence of different chemical components within it.

SORS, which was originally developed at STFC’s Central Laser Facility and is celebrating its 20th anniversary this year, is used in airport scanners all over the world through Agilent Technologies.

Results demonstrate that SORS can non-invasively verify the chemical identity of dominant substances in these fluids measured through a historic glass jar.

The method was also able to differentiate between different concentration points of components in water within the same type of preserving fluid.

Valuable new application for this technology

Sara Mosca, Raman spectroscopy scientist at STFC CLF, said, “It has been a privilege to contribute to this innovative research, applying our SORS expertise to help uncover a valuable new application for this technology within the heritage science community.”

Chelsea McKibbin, senior conservator at London’s Natural History Museum, said, “After many years of seeking an appropriate analytical approach, it is exciting to be part of this enthusiastic project.”

Applying this technique in practice to historic fluid preserved collections where minimal intervention is paramount, will not only be invaluable to collection knowledge, but also inform future care considerations.