Developed film not transparent

[Glen Brownson]

My first go at home developing 16mm film.

Three types of film snip tested, developed using Dektol, fixed using a solution of water and sodium thiosulphate. 

Very old Svema B/W reversal film - exposed image developed ok, however on fixing the film remained virtually opaque, some slight improvement in transparency, but negligible.

Suspecting that the fix was not working properly, tried different concentrations and soak times, still no improvement.

Tried with two other old B/W film; Kodak 7231 Plus-X negative, and Ilford FP4.

The FP4 behaved as I expected, black areas of development and clear areas. So it looks like the developer an fix are both working OK.

The Kodak stayed opaque black both sides.

Question 1:  What Is the reason for the opaqueness of the Svema film? Was it due to it being very old? A visible image was present on the emulsion, but not visible from the reverse side.

Question 2: What is the reason for the opaque black of the Kodak film? I thought Rem-jet was only used on colour film - was I mistaken and there is rem-jet present?

Many thanks

[Simon Wyss]

You developed simply to negative, didn’t you? Reversal films need to be reverse processed which imcludes bleaching and dissolving the just developed negative image out the film. The remaining silver halides must then be exposed to light and blackened in a second developer bath, finally fixed and washed.

True reversal films have an anti-halo undercoat between the base and the photographic layer(s). Agfa Scala has a manganese dioxide AHU, Fomapan R has a pure silver AHU. Svema supposedly has a manganese dioxide subbing, I don’t know their films well. After simple development the undercoat is still in place, opaque.

Kodak reversal films have no subbing since 1957 but rather a grey or blueish base plastic, dyed in the mass. They’re not true reversible films as the older ones were, Panatomic-X, Super-X, Super-XX. Like a negative film such as Ilford Pan F you can develop them to negative or invert to positive. Maximum density will not be comparable, though.

[Glen Brownson]

Hi Simon. Yes I developed to negative. I knew that the other steps were required to produce reversal film, but thought the final fix after initial development would clear the film. So, its good to know what the issue is.

The Kodak film is negative not reversal, so I was expecting that clear as normal. 

Thank you for your help.

[Charles MacDonald]

5231/7231 is a negative film, and will have a grey base.  SHOULD be clear enough to print from. (it actually was a nice film, I still have a couple of 36 exposure still rolls of 5231 stashed away)  perhaps the sample you tested was fogged?

[Glen Brownson]

Hi Charles, I don't think the film is fogged, it just looks black before development and after. I can see the matt coating after development on the glossy film, but no colour change. I'm awaiting some permanganate to make a bleach solution - I don't think that will help with this negative film, but I'll give it a go.

[Martin Baumgarten]

If using a B&W Reversal film that has that internal antihalation layer, it's usually dissovled in the Bleach stage.  Processing it as B&W Neg, I would first wash/soak the film for 1-2 minutes minimum, the Bleach preferably with a Dichromate Bleach formula, but you could also use an E-6 Color Reversal process Bleach.  The bleach only affects black metallic silver which has not formed yet, since the film has not been developed.  Rinse the film well, at least 3 to 5 minutes in running water, or at least a dozen water changes with agitation per change lasting 1 minute minimum.  Then go about processing the film as a Negative normally.  Since the antihalation layer has now been broken down by the Bleach, the exposed silver halides will convert normally to black metallic silver, and all soluables will convert out in the Fixer and then be removed by the final wash.  This is exactly what has to be done for those wanting to Negative Process the FOMAPAN R-100 Reversal filmstock.  FOMA does make a Negative version which would be easier to use, but I'm not sure if they are offering that in movie film formats.

[Glen Brownson]

Thanks Martin. I have been using a potassium permanganate / sulphuric acid bleach - do you think this is likely to work?

I did find some processing info for Svema reversal film:

https://www.filmkorn.org/super8data/database/accessories_list/tanks_docs/processing_svema_bw.htm

I tried this using desktol developer, permanganate bleach and hypo fix, as substitutes for the given chemicals. I don't have sulphite so could not carry out the clearing step. Although the dektol (first development) did develop a negative image ok on the emulsion, the subsequent steps removed this. No reversal image was present on second development. Is the lack of sulphite step the problem?

Neither bleaching nor fixing cleared the film. (excess bleaching eventually removes all emulsion and antihalation coating leaving clear film with no image).

[Martin Baumgarten]

The Sodium Sulfite returns light sensitivity to the remaining unexposed Silver Halide crystals which is needed for the reversal exposure (which I'm assuming you gave it via a strong light source).  The Potassium Permagenate Bleach is weaker than the older traditional Potassium Dichromate/Sulfuric Acid Bleach, so it might need longer bleaching times.....you can tell via visual inspection if the emulsion surface looks like a creamy light very light tan type color without any black metallic silver image remaining.  No need to waste film in testing, just use small short lengths and use a still film processing tank such as a Nikor or Patterson tank.  I still think as long as you washed the film well after the Bleach step and gave it enough light exposure, it should still react with the 2nd Developer and yield an image.  Various film formulations react differently, and old film which has already lost emulsion speed will not behave nominally.  Any existing Svema was definitely manufactured prior to 1992, and while it was a pretty good film in it's day, I don't think it has the sensitivity longevity of western mainstream films: Certainly a significant quality loss for modern usage after over 3 decades since it was made.

Dektol is a paper developer, but can be used for film, either straight or in various dilutions.  For your use, if used straight full strength, it should've yielded an image.  It's a strong fast working developer, thus its formulation for the processing of B&W photographic paper.

Svema is old school silver rich film, such as is Fomapan, thus the longer bleaching time on that chart.  But it also has to do with the mixing strength.   You can't really over bleach, but if the bleach is getting older, it is possible to stain the film yellow.  It's really important to do the Clearing Bath step.  I fully rinse the film well between all steps, and washing well after the Bleach step minimizes wear on the Clearing Bath. 

If you can't get the Sodium Sulfite at your local chemist, you might be able to get it from a swimming pool supplier.  All kinds of chemicals are used to maintain pool water PH.  I'm sure though it's available in England, since I lived over there and we used both KODAK and ILFORD chemistry.  I know how difficult it is getting analog materials from modern High Street camera shops that seem to cater to the digital world.  Just contact a film lab and ask where they get their chemistry from, or perhaps they'd be willing to sell you a small amount for personal use since they tend to buy in bulk anyhow.  Hope you can sort something out.

[Glen Brownson]

Thanks Martin, I'ver ordered some Sulphite and will see if I get a result.

Thanks for your help.