PIZZIGHELLI'S PROCESS In this is used a print-out platinum paper invented by Capt. Pizzighelli, of Vienna, in 1887. The exposure may be judged as accurately as with ordinary P.O.P., and development of the paper is unnecessary. Any good plain paper may be used,, and the sensitiser may be as • follows : A. Potass. chloroplatinite 734 grs. 168 g.
Distilled water . To oz. 1,000 ccs.
B. Ammonium ferric oxalate. 3i Oz. 412 g.
. Powdered gum arabic 31} „ 412 „ Potass. oxalate (5% sol.) 7 „ 700 ccs, Glycerine . . 100 mins. 21 „ Heat the potassium oxalate solution to about 115° P. (46° C.), and dissolve in it the ferric salt and glycerine; then add to the gum and stir well.
C. Solution B . . 3i oz. 1,000 ccs. Potass. chlorate (1 in 20 sol.) . . . 135 mins. 8o „ D. Potass. oxalate (5% sol.) drms. 535 ccs. Merc. chloride (5% sol.) 338 mins. 200 „ Gum arabic (powdered) 370 grs. 242 g. Glycerine • 34 mins. 20 ccs, C and D are sensitive to light and should be kept in the dark. For black images, sensitise the plain paper with the following :— A solution (platinum) . loo mins. 100 ccs.
B solution (iron and gum) 120 „ 120 „ C solution (gum and chlorate) . . . 4o „ 40 „
For sepia prints use— A solution . . . l00 mins. Ico ccs.
C solution . . . 8o „ 8o „ D solution . . . 8o „ 8o „ Day the paper on a sheet of glass, working in a yellow light, and apply the sensitiser with a pad of cotton-wool. Dry quickly and preserve in a calcium tube. Print under a negative in daylight until the image is fully out, and then dear by passing through dilute hydrochloric acid (, in 8o) ; finally wash for from fifteen to twenty minutes in clear water.
The time of printing Pizzighelli paper may be shortened if, after the deepest shadows have appeared, the prints are developed in a cold 5 per cent. solution of potassium oxalate or common washing soda. The following bath has also been recommended in place of the hydro chloric acid bath : Copper sulphate, 154 grs. ; water, 34 ozs. The Pizzighelli process cannot be depended upon for regular tones.
Pizzighelli also invented a paper of the " Pellet " type. (See " Pellet Process.")