A number of authors have on the basis of experiments determined that pressure and gas density can have an influence on bubble formation size. Usually this influence is attributed to the gas momentum force, generated by gas flowing into the bubble during its formation. In this article the theoretical bubble formation model of Tan and Harris has been used (and slightly altered) in order to demonstrate (by comParing model calculations with literature experimental data) that gas properties and pressure can have a considerable influence on single-bubble formation even for conditions where the gas momentum force is still negligible. Finally, these results are also used to explain some observations that have been made in bubble columns.