Sense-Sifters were instruments used in Sanctaphrax which detected the emotional undertones of the weather. Small, silver boxes mounted on tripods and inlaid on each of their sides with material made from the wings of emotion-sensitive Woodmoths, Sense-Sifters changed color according to the mood they detected in the atmosphere. Joy turned Sense-Sifters pink, rage turned them red, sadness turned them blue, fear turned them yellow, and madness turned them purple. Usually any emotion in the atmosphere was too mild to do anything but turn Sense-Sifters a very light shade of pink or blue, but they were known to go completely haywire during Mind Storms. There were only two Sense-Sifters in Sanctaphrax: one in the Loftus Observatory, and the other in a run-down Viaduct school, the Department of Psycho-Climatic Studies.