Our research on the formation of craquelure patterns in the painting layer requires a study of the mechanical properties of its components. Thus, this week we have been measuring the fracture toughness of the gesso. During this experiment, we have been following the crack propagation using a video extensometer together with acoustic emission, which enabled us not only to see but also to hear the crack!
Measurement system for fracture toughness determination. 
Recording of the video extensometer during the measurement.
This research is a part of the GRIEG project (2019/34/H/HS2/00581) financed through the National Science Center Poland from the Norway Grants 2014-2024.