A novel technique has been developed for measuring heat pulses in liquid helium without disrupting the beam of excitations. Bolometers are made with a thin film of superconductor (Zn) evaporated onto a 20 mu m diameter glass fibre. The authors describe a method for reliably producing Zn films, and for subsequently mounting the fibres in the experimental cell. A model is developed to explain the measured DC characteristics of the bolometers. It suggests that in the resistive transition region the superconducting film has an inhomogeneous structure. From these measurements a value of the Kapitza conductance H_K=130 W m^-2 K^-4 is estimated. This is in reasonable agreement with values reported by other authors.