Ken writes:
>Why would you want mortars to be softer & more plastic when wet?<

Brick doesn't really expand/contract all that much with changes in
temperature - the linear coefficient of thermal expansion is relatively
low. But it does expand and contract significantly with changes in moisture
content. When bricks are being wetted and undergoing relatively rapid
volume change, mortar which is more plastic can accomodate the change, with
minimum stress to the brick. That seems like a good thing to me.

Mike Edison