a solargraph is a pinhole version of what Nicéphore Niépce, one of the early inventors of photogrpahy,
called a retina print. he used a camera and lens rather than a pinhole.
solargraphs, unlike lumen prints, are more of a silver stain, not a chemical reaction.
with lumen prints the emulsion sweats, the plants sweat as they are left in the sun compressed onto the paper,
so there is a reaction. lumen prints can be fixed and toned. people use gold or selenium or other things to tone them
and a weak hypo bath to fix the images. from what i understand they print them darker than what they want
because the fixer bleaches the image and makes it faint ....
with the retina prints / solar graphs fixer removes the image entirely. it turns the paper completely white.
i plan on using a super saturated salt solution with my own retina experiments. talbot used a supter saturated
salt solution to fix/stabalize his images before hypo was suggested, and people here on apug, and elsewhere have used
salt solutions to fix film, so it is worth a try
the thing about using a scanner, is that it fogs the image so you only get 1 or 2 tries, it is pretty tricky.
what i usually do is scan the image barely tweak it in PS.
i can't speak for anyone else .. who knows maybe they boost it a bit, but probably not ...