Photoflash lamps

Claim 1

A flash lamp comprising, in combination, a borosilicaTe glass light-transmitting envelope consisting essentially of the following constituents in ranges by weight of 60 to 75% SiO2, 10 to 25% B2O3, 1 to 10% Al2O3, 4 to 10% total alkali oxides and 0 to 5% BaO and having a coefficient of thermal expansion of about 40 to 50 times 10 7 per degree C and a volume of less than 1 cc, a quantity of stranded combustible material consisting essentially of hafnium distributed within said envelope in an amount from 28 to 52 mgs, said strands being minutely kinked into bends at a multiplicity of closely spaced points along the lengths of the strands corresponding to about 20 to 40 bends per 4-inch length of strand, a quantity of a combustion supporting gas at a pressure of from 10 to 26 atmospheres within said envelope and in an amount from about 80% to 150% of the stoichiometric quantity required for chemical reaction with the combustible material, and ignition means for igniting said combustible stranded material mounted within said envelope by means comprising a metallic member having a coefficient of expansion substantially matching that of the glass and being sealed to the glass envelope, said flash lamp upon flashing generating a total integrated light output of from 14,000 to 32,500 lumen seconds per cubic centimeter of envelope volume at approximately 40 milliseconds after ignition.