Bubble formation in a single sample of pure water, held in the sample holder of our automated lag-time apparatus, is shown to lead to accelerated liquid-to-crystal heterogeneous nucleation. This phenomenon shifts the entire probability distribution for heterogeneous nucleation, together with the average lag-time , to significantly warmer temperatures. In the linear supercooling experiment analyzed here, this is equivalent to reducing the average time to nucleation. Using a single assumption tested in previous work, the entire 'nucleation curve' is extracted from a single experiment. (C) 2002 Elsevier Science B.V. All rights reserved.