I worked in a biology lab in college… we had this stuff called Picric acid that was used as a reagent in certain experiments and stains.
Its somewhat explosive when not wet.. you need to store it in water…
Mix Picric acid into latex paint, paint on door frame, let dry.
Next time they close the door it will likely blow the thing off the hinges.
This is probably a really bad idea… I shouldnt have mentioned it ^_^;; I dont think you can get the stuff without a permit anyway… because of its properties.
There was also another lab reagent called phenolphthalein that when consumed would turn your urine bright pink (it is a PH indicator solution). It is a common ingredient in laxatives so I believe its safe for consumption. Not sure where you could get this in it’s straight form however.
I miss that job.. was a college work-study thing