Hello Jim,
I have followed this thread with interest and would like to suggest
that maybe the forging of ingots and the effect of the surface
crystal structure on re-crystallisation is metallurgy 201? 
But
seriously, particularly for small scale, chill cast ingots the
forging techniques demonstrated by Leonid where he works the surface
at 45 degrees to the direction of casting will have a beneficial
effect on the subsequent re-crystallisation of the surface grains
when they are annealed. For those that want a more technical
explanation, in addition to the two books recommended by Jim, 'The
Plastic Deformation of Metals by R W K Honeycombe gives more detailed
about grain structures and the effects of annealing and
different working processes.
Where silver alloy sheet is produced commercially by continuous
casting, the ‘surface skin’, which the forging process that has been
discussed effects, should be removed by a scalping or a milling
operation prior to rolling commencing to ensure good surface quality
in the finished sheet. In addition, the commercial rolling mills
used for sheet production allow the centre of the cast strip to be
worked due to the significantly higher roll pressures that can be
applied compared to those available using ‘silversmiths’ rolling
machines. In all of this discussion I would highlight two points that
have made to help with quality sheet production; get a significant
reduction into the cast bar/strip (at least 50% reduction in
thickness) before annealing and also get the annealing correct. It is
important to heat the metal for long enough to get proper
re-crystallisation of the grains occurring, not just a drop in
hardness.
Charles Allenden