Unsigned paintings by students from the school of the Danish flower painter J.L Jensen (1800-1856) may be become forgeries by addition of a false signature. In such cases it is difficult to tell whether or not they are authentic as almost all aspects of the paintings may be the same: the same motifs, the same colours, the same materials and so forth. Using a brushwriting analysis may be one method to establish authenticity. Brushwriting is defined as the traces which the brush has created on the painting. The brushwriting of J.L. Jensen has been established by studying the surface of a selection of his paintings of reliable provenance. A number of brushstroke patterns were found. The signature of J.L. Jensen was also identified. Subsequently the brushstroke patterns were compared to those in flower paintings by other painters in a negative control analysis, in order to examine the extent to which J.L. Jensen’s brushstroke patterns are unique to him. This comparison provides indicatio