Am I "throwing money away" by not being more anal about separating
my smaller fine silver scraps from my sterling scraps? (Right now
there does not seem to be a whole lot, but as my business grows I
would imagine and hope, that I will be producing more.
You are doing just fine. If you compose your alloy with precisely
925 parts of fine silver, out of 1000, some of the alloy may actually
be bellow the standard. Edges of an ingot usually contains less
silver than middle part. Difference is minor, but enough to warrant
practice of using slightly more fine silver than required. This is
caused by pouring at higher temperature than necessary, which is
almost unavoidable in small shop practice.
Additional benefit is that sterling crystalline structure can be
damaged if brought to temperature necessary to work with hard
solders. (See Brepohl for more explanation) Alloy of 950 part of
fine silver is much better choice. But even if your alloy is less
than 950, any increase from 925 is beneficial.