The temperature stability of cylindrical domains in a hexagonal array in basal cobalt foils has been investigated theoretically and experimentally. Minimisation of the total energy shows that below a critical value of the anisotropy constant the magnetization begins to tilt from the c‐axis, Lorentz micrographs vindicate this prediction and show that the spin distribution in a bubble changes symmetrically to produce a Bloch line in the centre. It is thought that the results of these experiments indicate possible nucleation mechanisms for bubbles.