A thermographic method has been developed, in order to study in-plane non-uniformity during through air drying of paper tissue products. Non-uniformity in drying of paper is unavoidable, due to the heterogeneous nature of the product. It can be detrimental to the quality of the product, and significantly lower production capacity. The method utilises the endothermic nature of the drying process to quantify non-uniformities. The temperature varies with amount of remaining water. The method is here applied to through air drying of tissue paper, but could also be used for conventional contact drying of other paper grades.