One should distinguish between scratches
-) on the emulsion side
-) on the base side
(In case the base has a dulling layer refer to the first case. Antistatic surfaces on the base should be of no interest I assume.)
The refractory index of gelatin is said to be 1.51 (with listings going from 1.465 to 1.550)
A coating of some thickness (with the same ref.index as gelatin) on the emulsion side could reduce contrast but could also make image details visible again.
(Tri-) Acetate has a refractory index of 1.48
Polyester of 1.64
a) Coatings in order to fill the scratches:
Glycerine has a refractory index dependend on the amount of water absorbed covering the range given above.
Tetrachlorethylene: 1.50 (very volatile though)
A mixture of 9 parts Toluol an 1 part 1,1,2 Trichloro-1,2,2-Trifluoro-Ethane: 1.50
Oil of cloves*l: 1.55
*could be mixed too
(the tolerance between emulsion or base and the coating should be within 0.02 .
b) Coatings just to give a dulle surface in order to countereact the refractory effect,
c) dulling by another means,
d) Smoothening the gelatin, and thus the scratches, by repeated swelling and drying
I got all these ideas from a publication of our fellow member Gigabitfilm, who once made a factor-1000 enlargement of a pictorial negative and thus looked into film-surface problems.
Last edited by AgX; 12-22-2007 at 04:25 PM. Click to view previous post history.