If a conditioned room is not available, maintain the humidity by means of a saturated solution of ammonium nitrate contained together with the solid salt in a wide dish, and placed in a tightly-closed cabinet. Keep the air in the cabinet moving over both solution and plaster.
Fill a ring mould made from a rigid material, 100 mm internal diameter, 25 mm internal depth with the paste under test. Rest the mould on a non-porous plate, fill it by using a flexible palette-knife in about ten increments in such a manner as to eliminate voids or air-bubbles. Smooth off the surface of the paste level with the top of the mould.
Drop a 25 mm diameter methylmethacrylate ball of weight 9,8 ± 1 g from rest from a height of 250 mm measured from the bottom of the ball to the surface of the paste, so that it falls approximately into the centre of the ring. Record the penetration as the distance from the lowest point of the ball to the level of the original surface of the material.
The appearance of the product shall be examined for changes in e.g. colour, texture, shape and for the appearance of cracks, fissures etc. If changes in appearance are not reflected in the results of the examination of the other properties given in 188.8.131.52.3.2, possible consequences of the changes in appearance, on durability, should be assessed on a case by case basis.