nip 28 to increase the dwell time of the web 26 in the nip 28 increasing the nip width is accomplished by making the compliant cover 32 softer however if this is done with a single layer of soft material two problems with soft calender rolls are aggravated the first is that the cover is more likely to separate from the inner metal shell 30 because of the greater shear stress at the interface between the cover and the metal shell the second problem is that the greater deflection in the thickness of the cover results in greater hysteresis heating the soft cover compliant roll 24 overcomes this problem by using multiple layers 34 36 38 40 which are progressively softer as distance from the metal shall 30 increases the first layer 34 has a very high hardness 0 4 pusey and jones the second layer 36 is slightly softer with a hardness of 5 to 10 pusey and jones the third layer 38 has a softer layer with a hardness of 10 15 pusey and jones and the final layer 40 has a hardness of 15 to 30 pusey and jones by using a series of layers with increasing softness the shear at the interface between each layer is reduced so that separation of the roll cover 32 from the metal shell 30 is reduced because the last layer 40 is relatively thin it can be softer thus allowing for a greater nip width and so greater calendering effect ideally the hardness or durometer of the roll cover would vary continuously from the shell 30 to the surface of the roll cover 32 however practical considerations suggest that separate layers be used to develop the roll properties materials suitable for achieving the properties required for the.