Show for secret writing most invisible inks inias are made with paste drier as a base and one of the mineral salts baits its a coloring medium cleat Is used to develop the printing and moisture to make it disappear 0 0 the chemicals pos possessing gessIng this pr property are cobalt chloride barlum barium sul sulphate barium nitrate copper chloride dilute sulphuric sulp hurle add acid potassium nitrate and equal parts of 0 alum and garlic juice another form of invisible ink to la made from a mixture of transparent tint base end paste drier it Is invisible when dry but shows up clearly when rubbed with an ordinary lead pencil |