> I want my images to be true to what they would have looked like in
>the 1860s.
My use of sepia is aimed at getting a warm tone. The Civil War and turn of
the century work I have done, I used a split tone, first a light selinimum
tone, then the etch and sepia. The selinium toned areas will stay blackish,
while the lighter tones will go toward the browns, but will be light. After a
little experimenting (I was using Oriental Seagull, which is no longer
available), I was able to get the effect I wanted. Note I said the effect "I
wanted," not necessarily exactly correct, but what I felt like the picture
needed.
I have not spent the three months (that it took in the begiinning with the
Seagul) experimenting with other papers to get that same tone effect. All I
now is that I have not found a paper that duplicates it (yet).
Someone else may give you a scientific or other esthetic answer. That was
mine.
Don