Cherry Kino

Cherry Kino

Monday, 1 July 2013

New way of developing b/w reversal film - without sulphuric acid! Hooray!

Hi everyone!

I've just watched a test strip of film that I developed using an alternative to sulphuric acid for the bleach part of the black and white reversal process! I'm totally thrilled! It has come out beautifully. I have always avoided using sulphuric acid to mix my own bleach because I'm quite freaked about how utterly volatile and dangerous it can be. I know there are safe ways of working with it, including loads of ventilation and goggles and lots of protective gear, but I didn't fancy having to spend loads of cash on stuff like that. And sometimes, when I have a real aversion to something, despite assurances it's all ok, I like to listen to my gut. So, for a few years, I've mostly been developing colour film, or else developing b/w film as a negative process, or using a fomapan reversal kit (which isn't brilliant for Tri-X - it makes footage shot on a sunny day look like it was really overcast, and it's pretty pricey too).

So I found out about an alternative solution on the website which involves using 65 g/L sodium bisulfate and 10 g/L potassium dichromate. For photographic / cine developing purposes, this is almost identical to the sulphuric acid bleach, because the resulting solution is chemically identical to an equal mixture of sodium sulfate and sulphuric acid, and the sodium sulfate is photographically inert! Genius!

It's basically R9 bleach!

Because sodium bisulfate is a powder, and behaves differently to how acid behaves, it is so much easier and safer to use. Of course the potassium dichromate, the other powder used, is seriously dangerous to health and should absolutely never be inhaled, and spillages should be cleaned up promptly otherwise they dry and the powder gets into the air and can be inhaled, but at least cutting the sulphuric acid out of the equation means there's one less thing that could go wrong!
A little extra info about potassium dichromate, courtesy of Florian Cramer (thanks Florian for flagging this up). It is seriously nasty stuff, so utmost care people!!

"But as you write in your original posting, people should be aware of the health risks of Potassium dichromate which according to Wikipedia is "one of the most common causes of chromium dermatitis; [...] especially of the hand and fore-arms, which is chronic and difficult to treat. Toxicological studies have further illustrated its highly toxic nature. With rabbits and rodents, concentrations as low as 14 mg/kg have shown a 50% fatality rate amongst test groups. [...] As with other CrVI compounds, potassium dichromate is carcinogenic and should be handled with gloves and appropriate health and safety protection. The compound is also corrosive and exposure may produce severe eye damage or blindness.[9] Human exposure further encompasses impaired fertility, heritable genetic damage and harm to unborn children."

Here are the timings I used for developing my test strip of Tri-X b/w reversal Super 8 film:

first developer - D-19, 7 mins
bleach - 65 g/L sodium bisulfate (NOT bisulfite!) and 10 g/L potassium dichromate, 3 mins
clearing bath - 50 g/L sodium sulfite (NOT sulfate!), 1 min
re-exposure to light
second developer - D-19 (same as first dev), 4 mins
fixer - non-hardening (only because I intend to tone the film), 4 mins
rinse - 15 mins

Et voila!

Very pleased. Has really worked brilliantly. Off to process 3 full Super 8 films now, and get on with making that music video for 'Kiwi', the single by Leeds band 'Just Handshakes'.

The developing is only a tiny first step - then comes toning by hand using brushes on each individual frame. Not to mention the editing! I have so much work to do at the moment, better go and get on with it!

Thursday, Friday and Saturday were spent teaching children Super 8 filmmaking in Cambridgeshire. It was ace fun. I spent a day with 6 year olds on Thursday! They were so sweet, and really focused on the filmmaking, I was totally impressed. The next day I spent with 9-13 year-olds doing b/w filmmaking with caffenol and applying colour by hand, and the day after that was shooting colour reversal and cross-processing it, with 8-14 year-olds. I slept for England afterwards!

My friend Marko from Bristol also sent me an email about how mac laptops are totally influenced by the design of Braun Nizos! It was a revelation - but one that makes perfect sense when you think about it! That brushed steel look - total winner.

Enough film geekery for now...


x Martha


  1. Hi,
    This is Peter from Sydney.
    Found this via Frameworks.
    That's great info about the bleach sans sulphuric acid.
    You know to be super careful with the Potassium Dichromate as well. It's nasty stuff.
    Look forward to seeing the results. Will you post here?
    Seems we're doing similar things and at similar stages!!
    All the best.

    1. Hi Peter from Sydney!
      Yes, I know the Potassium Dichromate sucks big time. Florian Cramer sent me a similar email with full details of all the nastiness it's capable of causing in the human body, so am just about to add that to the post too. I knew it was awful, but not just quite how awful. Here's hoping someone comes up with an alternative to that soon too! :) Thanks for your message! x Martha

  2. Hi

    Sounds great. Can you use caffenol as the dev instead of D19?


  3. I'm experimenting with Caffenol developer and Hydrogen Peroxide / Citric Acid bleach to avoid the whole toxic chemical issue. Still developing it but early tests with old expired Kodak 7241 (E4 process) seem promising. See my video, with formulas and times here:
    So far its much slower than other bleaches but I'm hoping increasing the temperature will reduce the time. 7241 has to be developed at low temp or the emulsion slides off (even with prehardener), so I'm now moving on to Kodachrome which should be OK at 38C

    1. Having a look at your video just now, I like the sound of it as the acid based bleach thing worries me greatly and having a pet around, (cats are curious), it worries me further now I don't have a dedicated darkroom.

  4. Wonderful post. This is nice post and gives in depth information.

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  5. This is really interesting.
    I'm a stills photographer and have gotten into the videography side of thing due to Youtube and started using Hi8 onto MiniDV and finally digital as most who started youtubing before decent SSD digital became viable but that aside, i'm more and more attracted to the beautiful look of super8 footage, Having borrowed a camera and gotten an old roll of Boots, (I think), colour reversal I'm itching to have a go but being a film photographer who used to have a full darkroom, (I kept the basics and still shoot film and develop my own negatives), I want to develop my own, I bid on a LOMO tank on ebay and am awaiting that BUT...........
    Finally to my question, do you do classes or groups on using developing and such with super8?
    I'm in the Highlands but often travel to yorkshire to catch up with family and friends and would really love to join a group of like minded super8 newbies who are keen to get more knowledge and info.



  6. I used a Kodak kit for reversal B&W. That was long ago. I don't know what was in the kit, but I doubt it contained sulphuric acid. I had a long career in photography as a pro. This included E-4 and E-6. Now, I want to mix my own, and use it with Ilford Poly F. I am not concerned about hazardous chemistry because I know how to be safe. I hope to continue to follow this, and get a 100-foot roll of Poly F ordered. Cheers

    1. Ilford motion picture film is lovely, but they stopped producing it in 2003, where are you ordering it from - I'd love to get my hands on some?

  7. Hello Martha, can I use this technique with the Super 8 b/w Adox please?
    Thank you,

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  10. prof prem raj pushpakaran writes -- John Brown Francis Herreshoff, the great metallurgical chemist who invented process for making Sulphuric Acid was born on February 7th 1850!!!