Thin strip casting of steel through a twin‐roll caster demands the production of a perfectly homogeneous strip. This requirement is often not fulfilled due to non‐uniform heat contact between the solidifying strip and the rolls in the pool, which leads to temperature inhomogeneities visible at the strip behind the rolls (spottiness). The effect of spottiness is described from experimental observations in terms of contrast between dark and hot spots and of the mean diameter of the hot spots. The contrast is found to depend on roll material, surface roughness and roll velocity. A general dependence on the temperature difference between melt and rolls is observed.Calculations of heat transfer in the liquid and solid pool explain the hot‐dark‐temperature differences. The spottiness visible on the strip after leaving the rolls is initiated in the liquid pool, but it is enlarged by rolling contact differences in the solid pool. A model consideration based on thermally caused bending of the solidified material layers leads to a good coincidence with experimental data of the heat transfer coefficient at hot spots.