The Effects of Gamma Irradiation on Historic Pigments

Author: Valentina Bakša
Mentors: Associate Professor Zvjezdana Jembrih, MA; Associate Professor Vladan Desnica, PhD

Academy of Fine Arts, Zagreb (Croatia)
Study programme: Conservation and Restoration of Works of Art
Specialization: Sculpture (5th year of study)

Baksa VAbstract

It is common to subject wooden objects to some sort of desinsection, before treating and storing them in the depot, in order to prevent the activities of microorganisms and other pests and contamination of the nearby wooden objects. The most common desinsection method used in recent times is radiation with intensive gamma rays, e.g. using radioactive cobalt 60. The dose can vary depending on the type of pest. Thus, a sculpture infected by microorganisms requires a higher amount of gamma radiation than a sculpture infested by worms.
In order to examine the possible impact of radiation on discoloration of sculptures, we submitted different paint layer samples to various amounts of gamma radiation and compared them after exposure. The investigation focused on the pigment types identified on the sculpture of the Blessed Virgin Mary from Hromec chapel (which had also been exposed to gamma radiation), but the investigation also included other frequently used pigments. Four types of priming were applied to a cardboard and overpainted with pigments mixed with different binders. To ensure an objective characterisation of colour and its visual alternations, the fibre optics reflectance spectroscopy (FORS) was used.

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Short biography

VALENTINA BAKŠA was born in Zagreb, in 1992. In 2010 she enrolled into the Department of Conservation and Restoration of Works of Art of the Academy of Fine Art, Zagreb, specializing in  conservation of polychromed sculpture. During the course of her studies she has worked on the sculptures of the Suffering Christ and Blessed Mary with Jesus from Hromec, under the guidance of Assoc. Professor Zvjezdana Jembrih,  and on the decorative frame of the painting Immaculate Conception, under the guidance of Assoc. Professor Tamara Ukrainčik. In 2013 and 2014 she participated in the conservation treatment of several wooden polychromed sculptures at the Restoration Centre Ludbreg,