The LIGO (Laser Interferometer Gravitational-wave Observatory) has remote sites at Hanford, Washington and Livingston Louisiana. At these sites laser beams traverse 4km long 1.2 meter diameter beamtubes in vacuum to make the gravitational wave detection. The vacuum requirements are pressures less than 10^-8 torr of hydrogen and smaller pressures for heavier and more polarizable gases. The talk will describe the science and techniques developed, including: outgassing models, outgassing measurements, optical properties, material preparation, surface cleaning, bakeout and leak detection.