This experiment is designed to investigate the fundamental mechanisms for pool boiling on a horizontal surface. The unique feature is the combination of an artificial re-entrant cavity and a multiple sensor conductivity probe located above it. With this arrangement the bubble size and frequency were measured. Furthermore, the number density of the nucleation sites is prescribed (i.e. the single re-entrant cavity built into the heater surface). These basic data were not previously available for liquid metals with magnetic fields. The most striking result is the suppression of boiling at high values of the magnetic field. Good agreement between the data and a mechanistic model were obtained provided that the bubble frequency was known. The effect of the magnetic field on the bubble frequency needs to be resolved for closure.