[en] The data expression was received for calculation of hydrodynamic force acting upon a vapour bubble. Investigated was also the character of the bubble growth and its break-away from a heated surface. The photographic investigation of water boiling on flat heated surface was made at atmospheric pressure in conditions of natural convection, the surface being situated horizontally and vertically. It is shown, that bubble break-away is not conditioned unambiduously by gravitational force only, but is the consequence of steadiness losses of phase interface in its base. The dynamic wetting angle THETA and contact area of the bubble with a heated surface are connected with hydrodynamic force, acting upon a vapour bubble. The bubble break-away from the heat trasfer surface occurring at angles of THETA > 70 deg. The suggested new calculation expression for hydrodynamic force calculation, acting upon a vapour bubble is in a good agreement with the experimental data