The discovery of brain tissue during Mount Vesuvius’ 79 CE eruption at Herculaneum enabled the transformation of such tissue into organic glass through vitrification. Human brain preservation in archaeological sites is rare, with standard methods including dehydration, saponification, tanning, and freezing, but vitrification was previously unknown until this discovery. The researchers analyzed human skull remains from Herculaneum to identify the brain tissue that had turned into organic glass.
The research investigators utilized Differential Scanning Calorimetry (DSC), Raman spectroscopy, and physical and chemical tests to establish that brain tissue formed organic glass structures during high-temperature relaxation. Researchers documented this transformation occurring between 420°C and 510°C, marking a previously unrecorded process in human tissue preservation. Raman spectroscopy analysis showed increased order patterns in the carbonaceous tissue part, providing crucial evidence regarding the transformation into glass.
The materials underwent different analytical tests, including micro-imaging and density and porosity assessment, ts in addition to chemical composition evaluation. Research permits regarding human sample analysis were acquired through the Ethics Committee for Biomedical Activities, AOU Federico II, Italy, Naples, and Protocol N. 101/17. The analysis of uncoated samples C1, C2b, C102, and C117 occurred using a Zeiss Sigma 300 Field Emission Scanning Electron Microscope (FE-SEM) while operating in variable conditions, including accelerating voltage under different imaging points. These tests occurred at the Department of Science, University of Roma Tre. The same department used a hydrostatic balance to measure the sample densities of C1 and C7. The Nikon XT H 225 ST Tomograph equipped with a Perkin Elmer 1620 (Remet S.A.S) produced the 3D microtomographic image of C1. The device used for determining chemical composition was Energy Dispersive X-ray Spectroscopy (EDS). EDS System Quantax was used for elemental analyses featuring XFlash detectors at the Department of Science at the University of Roma Tre.
Vitrification occurred before the volcanic deposits entombed the body because the annealing of glass would not occur during the gradual volcanic cooling process. The determination of glass transformation temperature at volcanic cooling requires the melted viscosity data across temperature conditions. Information about the glass transitions enables researchers to establish cycles between heating and cooling processes at known speeds for extracting the unknown cooling rate.
During the experiments, structural relaxation of the glass material was observed at Tf temperatures ranging from 420°C (25 K min⁻¹) to 510°C (1000 K s⁻¹). These conditions enabled the investigation of the heat conditions surrounding the quenching process. The experiments have limited uncertainty while providing restrictive evidence to determine that 510 °C and 1000 K s− 1 accurately represent both the glass transition temperature and cooling rate of the sample.
According to the research findings, the vitrification process started when the hot ash cloud enveloped the body at temperatures exceeding 510°C. A quick cooling occurred after the ash cloud when environmental air replaced the high temperatures and allowed the brain to transform into glass. Scientific research indicates that the brain tissue survived destruction due to skull and spinal protection, which enabled the preservation of vitrified remains.
The primary constraint is the temperature of the pyroclastic deposits surrounding the vitrified brain fragments, which have been analyzed by paleomagnetism and charcoal reflectance and indicate deposition temperatures of 315 °C to 465 °C. These high temperatures suggest two important points: first, the pyroclastic material must be cooler than the Tf of the brain to retain the glass; otherwise, the brain would have turned back to soft tissue. Second, brain vitrification must have happened before entombment by pyroclastic material since glass formation cannot happen through the slow cooling of these deposits.
Scientists now possess evidence of human brain tissue vitrification, which provides valuable research opportunities for extreme condition biological material preservation. The researchers documented the initial case of human brain tissue existing as organic glass because of rapid freezing in volcanic materials with high temperatures.
References: Giordano G, Pensa A, Vona A, et al. Unique formation of organic glass from a human brain in the Vesuvius eruption of 79 CE. Sci Rep. 2025;15:5955. doi:10.1038/s41598-025-88894-5
