View Full Version : Desensitizing Film?

18-Apr-2008, 13:28
I came across the following in a book dated 1948:

"Desensitize the plates by one minute's immersion in 1:2000 Pinacryptol yellow. Alternatively proceed in darkness"

It then goes on describe tray processing of the plates.

I took this to mean I can desensitize film and process in daylight, or not desensitize and process in darkness. Otherwise, why would I desensitize the film if I have to process in darkness anyway. Am I reading this correctly? What is Pinacryptol yellow? Does it mean to process in blue light and the Pinacryptol yellow blocks it?


18-Apr-2008, 14:33
You can desensitize film to develop by inspection, so your interpretation may be correct - if you desensitize you can proceed UNDER SAFELIGHT (not daylight).

Pinacryptol Yellow acts as both an anti-fogging agent (restrainer) and a desensitizer. It makes the film not sensitive to red-yellow.

You can also use Pinkryptol Green, which makes the film insensitive to green - and so you'd need green safelight.

18-Apr-2008, 15:37
Thanks. I just read the instructions for Amidol at the Photographers Formulary site, where it's stated that this dye can be used for DBI under a 40-60 watt series 3 wratten safelight. That's quite bright. I wonder how much time the film can be exposed to such light. The instructions read 1:200 rather than 1:2000.

18-Apr-2008, 15:43

Proceed under a dim safelight ... perhaps safer yet, proceed in darkness till you are near the point where you really need to see the film to see the results. A dim safelight, very dim is quite usable. There's a good article on developing by inspection at: www.michaelandpaula.com/mp/devinsp.html which is a bit more liberal about safelighting during DBI.


Glenn Thoreson
19-Apr-2008, 12:23
The data I have from 1943 says to not use the green kind for panchromatic film. It doesn't say why. It seems after desensitizing, you can develop by inspection under your normal safelight for brief periods. The light must be no closer than 4 feet to the film. 60 watts ??? That sounds like development to destruction to me.