per "Kodak Photographic Retouching" CS is both a retouching medium and a doging dye. Since most papers only sensitive to blue (not really with MG papers) adding red dye holds back exposure just like silver grains. Diluted to a pale pink wash it can be used to lighten shadows, and even intensify highlights. Looking though a green wratten 68 filter lets you see how the print will see the effect. It is very water soluble so it is easy to remove.
add dye to the base side, since use on the emulsion side can cause the emulsion to swell. only small inticate areas should be dyed on the emulsion side. To dye a large area pre-moisten with a solution of one drop photo flo 200 per oz of water. this allows the dye to flow smoothly and evenly. Apply dilute dye, and build areas up.
To reduce and area quickly, use a 5% household ammonia soultion (one without detergents). Alternately use 5% solution of soduim dithionite, aka sodium hydrosulfite, (oth of which I have never heard of elsewhere). To remove dye everywhere, wash for 10 minutes, then phot flow bath, and hang to dry.
The full work flow summary for retouching a b&w neg is given as :
1) Clean the neg
2) make a proof print
3) premoisten the emusion side with dilute photo flo
4) reduce the neg areas locally as necessary with chemical reducers 1-3 min
5) wash thoroughly 10 min
6) dry dust free area
7) etch locally small areas
8) treat etched areas with abrasive reducer- a paste that softens the edge of etched areas
9) add CS or neutral dye to the base side. Use frisket (liquid maskoid) if necessary to confine the are the dye is to cover, then remove frisket
10) dry 15-20 min below 100F
11) add retouching fluid to the emulsion side and buff until dry and smooth, to keep film cleaner from wiping the retouching pencil off at a later printing stage. Not needed with Portra line, which has tooth for pencil retouching on both sides.
12) use stylus to remove pinholes
13) use pencil to retouch locally
14) sleeve neg until printing to protect your work.
