ABSTRACTThe functioning of a conventional heated platen laboratory press for paper or board press dry experiments is considered analytically and in the light of experimental results from the literature. A press dry sample dries so that the evaporation zone recedes from the edges toward the center. Since the dwell time of the web within a certain moisture content range influences the resulting strength characteristics, a conventional press dry experiment will not produce a uniformly strong web. To study the possible distribution of the strength deviation, a strength development function is generated and used in computer simulation of a web being press dried. The results emphasize the importance of dwell time as a factor in press dry strength devel oprnent. Finally, basic principles are reviewed or evolving an improved press dry laboratory device, and a model is proposed.