Abstract: An apparatus that is capable of continuously measuring the weight loss of a light weight, porous sheet material during drying while in constant contact with a heated surface. The resulting data may be converted to drying rate curves suitable for analyzing the effects on drying rate of furnish additives and processing conditions. The testing device is particularly useful for evaluating grades of paper or paperboard having basis weights greater than 50 g/m.sup.2. The device includes an electrically heated arcuate plate maintained at a constant temperature. The paper sample to be tested is brought into good heat transfer contact with the plate by means of a tensioned fabric that exerts a normal load on the sample but does not interfere with mass transfer of the vapor away from the drying sample. An air ventilating system provides a low turbulence flow of air uniformly over the fabric covering the sample.