Ed Huntress fired this volley in
:

It depends on what kind of mortar you're using. 'Better follow the
supplier's instructions.

Most lime mortars cure well wet or dry, but tend to effloresce if kept wet
after curing, about like plasters do, but not nearly so badly. Do as
block/brick/stone masons do. Put it on as wet as will sustain the load of
the stone/brick/block, and just let it cure until cheezy enough to strike
the joints -- then leave it be.

Lloyd