Study of the influencing effect of fire effluents on the proteinaceous paint layers

Fire disasters can pose a great threat to cultural heritage objects. The consequences of fire flames
and fire effluents (FE) are almost always disastrous and still represent uncertainty regarding how and to
what extent they affect the environment. Furthermore, their negative effect can continue long after the fire
has been extinguished. The fire behaviour can nowadays be monitored by different devices, such as cone
calorimeter (ISO-5660), smoke density chamber (ISO-5659), etc.
In this work, we employed bench-scale test in order to study the influence of FE on the
proteinaceous paint layers. Two sets of model samples (one containing lead white-egg yolk tempera paints
and the other pure egg yolk binder applications) were prepared to follow and to better understand the overall
fire impact (i.e., effects of temperature and FE). Untreated spruce was selected as burning material. Model
samples were placed in special chambers (influence of FE) and in a special designed holder mounted on
top of the cone calorimeter stack (influence of FE and increased temperature) during the exposure to FE.
Overall experiment lasted approximately 20 minutes, while the temperature on top of the stack varied
between 200 and 400 °C. Furthermore, the design of the experiment allowed the investigation of exposure
time. Molecular changes of exposed samples have been investigated by non-invasive reflection and
conventional FTIR, and Raman spectroscopy, while the colour change was evaluated by colourimetry. The
latter increased in relation to time of exposure due to either paint degradation, adsorption of effluents and/or
deposition of soot. The most significant changes were determined for the samples, exposed for longer
times. The appearance of additional IR band placed at 1,529 cm–1 suggested the presence of iminium ion,
which can form when protonated formaldehyde, generated by burning process of wood, react with protein
amine group [1]. Moreover, other alteration products such as lead oxide, were also detected.