The Dictionary Of Photography

A True Historic Record Of The Art & Practice Of Photography 100 Years Ago.

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Pinholes Pizzighelli's Printing-out Platinotype Process
Pinholes. Minute transparent spots making their appear-ance on the plate in the fixing bath. They are chiefly due to air bubbles, or particles of dust adhering to the film whilst in the developer, and thus preventing the action of the developer on the film at these spots. To obviate these the film should be brushed with a soft camel's-hair brush whilst in the developer, but where pinholes are in existence recourse must be had to retouching or painting them out with some non-actinic colour.
Pins. Convenient steel pins with glass heads can now be obtained from most photographic dealers ; these being very useful in fastening up prepared paper or prints to dry. The steel portion of these pins, as indeed all pins used in photo-graphic work, maybe usefully coated with thin sensitive bitumen varnish (see Clips and Asphalt Processes). Ordinary pins may be coated in large batches by dipping and collecting on a strainer; after which they may be exposed to light for a few days.
Pizzighelli's Printing-ont Platinotype Process. Rives or Saxe paper may be used, either glossy or with matt surface. The following solutions are required : -
No. i Solution, Gum Arabic.
Gum arabic (finest white lumps) ... ... 770 grs.
Distilled water         ............ 27 drms.
No. 2 Solution, Arrowroot.
Arrowroot ............... 30 grs.
Distilled water ............ 27 drms.
Mix the arrowroot into a paste with a little water, add to the remainder of distilled water whilst boiling, and keep the tempera-ture up for five or ten minutes. No. 1 solution gives the best effects.
No. 3 Solution, Ammonia Ferric Oxalate.
Ferric oxalate          ............308 grs.
Oxalic acid............... 8 ..
Ammonium oxalate            ......288 or 308 ..
Distilled water ............ 27 drms.