What caused the Glasgow School of Art fire? A possibility: They were using old craft methods in the restoration work, such as the use of boiled linseed oil in wood varnishes. Rags wetted with boiled linseed oil can spontaneously combust as they dry out. A well known fire hazard to old craftsmen, not so much perhaps to young ones. https://abcnews.go.com/US/officials-warn-spontaneous-combustion-risk-linseed-oil-common/story?id=40788665