reversal processing

[Paulo Roberto]

is possible reversal processing without bleach ?

 

[nworth]

I don't know of any method using ordinary film, but there are special films and papers that produce a positive image (often with high fog levels) using ordinary processing.

 

[Jordan]

Traditional B&W reversal is not possible without bleach. Without it, there is no way to chemically separate the negative and positive "images".

 

[glbeas]

I don't know of any method using ordinary film, but there are special films and papers that produce a positive image (often with high fog levels) using ordinary processing.

Graphic arts materials, there were some direct postive films and papers for lithography and halftone production. They were high contrast materials processed in the regular litho developers. As far as I know about them they were pre exposed to the solarizing point so any more exposure resulted in a loss of density, or some chemical equivalent. Maybe PE knows something about how they did it.

 

[Ian Grant]

As has been said no, but EFKE make a Direct positive paper Freesyle sell it. Kodak made a Direct reversal coping film it had an SO number, I still have some in the UK, it's developed in a normal print dev and gives full tones.

I guess I have over 30 different B&W reversal formulae and they all use a bleach. Some bleaches are worse (more hazardous) than others, but they include Bichromate/Permanganate/Persulphate/Quinone.

There are various formulae in the articles section.

Ian

 

[AgX]

Agfa too has such copying film on offer.

 

[Paulo Roberto]

I am trying to process a new microfilm from agfa ( ecopos 305 ). what kind of developer should I use ? the same first developer from the full reversal processing can be used as developer with the convencional fixer or I have to use a new kind of developer ?

tks

 

[Ian Grant]

Back in the early 1960's Dr Arne Arenberg & Leon Witten introduced the "The Arneleon System" for Reversal processing, this used 5 stock solutions allowing the first developer to be varied for different films. There were far greater differences between films in the 60's, thin emulsions like ADox KB14 (Now known as Adox/EFKE KB 25), and Pan F behaved quite differently to thicker emulsions, and particularly the very heavy coatings of Kodak Royal X.

Perhaps the most important feature is that Hydroquinone in the first developer is used to control the contrast of the final positive, it's the B&W Reversal processing equivalent of Dr Beers famous Variable Contrast print developer.

For a High Contrast films like Pan F the system used a Soft working Metol only developer, so you might have to use a similar approach to tame the contrast of a copying film.

Ian