Use of cobalt siccative in contemporary oil painting: a study of its behavior after accelerated ageing

Abstract

The present paper presents the results obtained after a study of the behavior of oil paint after addition of cobalt siccative in various ratios. This is a procedure particularly used by artists taking part in fast painting competitions, which require fast drying of their work, but also by many artists who shorten drying times of their works by using this substance. The study focuses on analysis of color alteration in pictorial layers after being subjected to ageing cycles in a climatic and photo-oxidation chamber. Particular emphasis has been placed on the study of color alteration as it is one of the factors that can affect conceptual aspects of contemporary works. For this reason, a survey was held among many artists, which yielded interesting data on ratios, use, and artistic intentions. After ageing (exposition to UV radiation for 900 hours and a temperature ranging between 10 and 50º C, with humidity also ranging between 60 and 90% for 500 hours), and having studied behavior through microphotography and colorimetry, it was concluded that UV radiation causes fading in pictorial layers, with most impact on blue tones, and that humidity and temperature ageing slightly darkens colors, placing stress on the priming layer and in tension areas close to the paint.