sentences:  The SF 1 fuze was constructed of glass and wood and contained a detonator and booster charge.Pressure of approximately 330 pounds (150 kg) on the pressure plate caused the plate to shear off from the mine casing, collapsing down on the glass head of the pressure fuze.The glass head was driven downwards, crushing two glass vials of chemicals, which reacted together causing a flash, initiating the detonator, booster and finally the main charge of TNT.