Experiments are performed on bubble detachment from an artificial cavity in a plane wall of a vertical rectangular channel. Mean upward velocity is varied. Steam bubbles are generated by local heating of the cavity, nitrogen bubbles of about the same size by injection. The experiments show a difference in take off direction between vapor and nitrogen bubbles. Steam bubbles take off into the liquid, while nitrogen bubbles more or less slide parallel to the wall. The bubble detachment radius decreases for increasing bulk liquid velocity, in a way that merely depends on the detachment radius without convection. Nitrogen bubbles, coming from a capillary with approximately the same radius are larger than water vapor bubbles. A force coefficient fit is performed on force components perpendicular to the wail. By analyzing flow- and non-flow experiments separately, some of the forces are quantified. By combining the results of nitrogen bubble and steam bubble experiments, a force due to the temperature difference at the bubble foot is studied. Such a force could explain the observed differences between steam and nitrogen bubbles. It is found that either a vorticity lift force of the type found by Pluton [The dynamics of bubbles, drops and particles in motion in liquids, Ph.D, thesis, University of Cambridge (1983)] is negligible, or this temperature difference force may be important. A commonly used criterion to predict detachment radii is found not to be satisfactory.