Soft emulsion from permanganate B&W reversal

Gerald C Koch · Jun 8, 2016

Not remembering much in the way of caution labeling for Cr(III) I looked up a couple of MSDS for the sulfate salt. They mention the salt being irritating to the skin, eyes and mucous membranes. Interestingly there was little in the way of toxicological information One MSDS did give an LD50 of 3000 mg/kg of body weight. Both forms listed environmental concerns as "Not available."

Photo Engineer · Jun 8, 2016

The equivalent of about 50 g/l of Sodium Sulfate is needed to reduce or prevent swell.

PE

Athiril · Jun 8, 2016

Okay, I think I've managed to get a working bleach from 'household'/supermarket chemicals.

Athiril · Jun 8, 2016

Alright I made a new thread for the topic, it appears to work on the first try:
(there was a url link here which no longer exists)

Rudeofus · Jun 10, 2016

Photo Engineer said:
The equivalent of about 50 g/l of Sodium Sulfate is needed to reduce or prevent swell.

If you have 40-50 g/l Sodium Bisulfate in your soup, it will be very acidic, and all that anti-swell action may be counteracted by the ridiculously low pH your soup ends up with.

Rudeofus · Jun 10, 2016

Alessandro Serrao said:
I don't have a damn clue of how much bisulfate is needed to anti swell the gelatine...

Alessandro Serrao said:
Sodium sulfate NOT bisulfate

Sodium Sulfate is fine. Based on your previous statements I thought you wanted to add enough Sodium Bisulfate to get the equivalent of 50 g/l Sodium Sulfate in Sulfate ions.

Photo Engineer · Jun 10, 2016

Whatever you do, the pH of an aldehyde (pre)hardener or a swell reducing version should be about 9.0. And you must wash before and after this solution.

If added to a bleach, then the pH should not be altered from the working strength of the bleach, but bleach times will increase - probably substantially.

PE

iandvaag · Jun 11, 2016

Thanks for all the responses.

A point on sulphate :
Na2SO4 • 10H2O : 322.20 g/mol (decahydrate)
NaHSO4 • H2O :138.07 g/mol (monohydrate)
H2SO4 : 98.079 g/mol

I'm presuming that when we talk about sodium sulphate, we mean the decahydrate. Let's see what concentration of sulphate ions that would be:
50g L-1 / 322.20 g mol-1 = 0.155 M

My recipe calls for 55g of sodium bisulfate :
55g L-1 / 138.07 g mol-1 = 0.398 M

Using Ilford's bleach, which calls for 10mL of conc. sulfuric acid, which contains about 18 mol L-1 :
18 mol L-1 * 0.01L / 1L = 0.18 M

If I assumed correctly that the figure of 50g/L sodium sulphate is referring to the decahydrate salt, then it does seem that the sulphate concentrations in the bleaches would have an effect, and the bisulphate bleach would have a stronger effect than a sulfuric acid one (as more sulphate ions are added to solution to produce the same drop in pH). As Rudi said, the anti-swell effectiveness of sulphate is counteracted by the very low pH, so this is all probably irrelevant.

In order to avoid increasing the bleach time due to the hardener, could the hardener be used later in the process, perhaps after the clearing bath, after a thorough wash? If I used formalin, how much would I need?

Photo Engineer · Jun 11, 2016

The pH is a critical aspect here.

PE

Photo Engineer · Jun 11, 2016

I've always said, "do what works for you" as there are so many possible combinations and outcomes.

PE

pepo007 · Oct 7, 2017

Hi,
I went through the post to determine formula for bleacher. So far for main components:

1, KMNO4 is strong oxidant, also leaving nasty marks on equipment. Also I found the eg. Ilford PANF 50 always get emulsion disolved. There are some way to soften strength,
but it is complex formula

2, K2Cr2O7 is pretty toxic, reason I'm trying to avoid

I read the is possible to use combination H2O2 (Hydrogen peroxide) and Citric acid. it is appear to me, since is easy wash after bleach.
Formula is 175mL water + 125mL 35% H2O2 + 8g Citric acid. Can be consider as right option?

Thx

Photo Engineer · Oct 7, 2017

It works, but can be slow.

PE

Rudeofus · Oct 8, 2017

I have never seen emulsion go away with Permanganate, but several times saw emulsion get damaged with Peroxide, and that was properly hardened color emulsion. The bleach formula you posted looks very, very concentrated.

Gerald C Koch · Oct 8, 2017

pepo007 said:
Hi,
I went through the post to determine formula for bleacher. So far for main components:

1, KMNO4 is strong oxidant, also leaving nasty marks on equipment. Also I found the eg. Ilford PANF 50 always get emulsion disolved. There are some way to soften strength,
but it is complex formula

2, K2Cr2O7 is pretty toxic, reason I'm trying to avoid

I read the is possible to use combination H2O2 (Hydrogen peroxide) and Citric acid. it is appear to me, since is easy wash after bleach.
Formula is 175mL water + 125mL 35% H2O2 + 8g Citric acid. Can be consider as right option?

Thx

Thirty five percent hydrogen peroxide is a very dangerous chemical. Contact with organic materials can cause explosions. Many rocket designs were powered by kerosene and 35% peroxide. The average person would have difficulty obtaining it. Even if you could find it there would be a stiff hazmat charge. The highest concentration of peroxide available over the counter is 6% used as a hair bleach.

railwayman3 · Oct 8, 2017

Years ago a friend and I tried to process some ancient Dufaycolor reversal films (basically a B&W emulsion on a ruled coloured base). We used the exact official formulae, time and temperature. but, when it reached the bleach stage (permanganate), the emulsion almost always stripped badly.

studiocarter · Oct 9, 2017

If anyone does successfully reverse 7266 16mm in a LOMO tank using Permanganate bleach, if so please post how to do it.

Anon Ymous · Oct 9, 2017

Rudeofus said:
I have never seen emulsion go away with Permanganate, but several times saw emulsion get damaged with Peroxide, and that was properly hardened color emulsion. The bleach formula you posted looks very, very concentrated.

I don't remember the exact experiment I did, but I splashed some 3% peroxide in a solution that had a film clip in it. Forgot about it, came back about 30' later and the emulsion looked like it was melting. I agree that so much peroxide will likely wipe the emulsion off the support.

studiocarter said:
If anyone does successfully reverse 7266 16mm in a LOMO tank using Permanganate bleach, if so please post how to do it.

I assume that Tri-X 7266 reversal film is not the ordinary 400TX, but I've successfully bleached 400TX using a permanganate bleach. I used half the amount of permanganate (1g/l) and 55g/l sodium bisulfate. Permanganate was dissolved in advance in half the volume of water needed and filtered with a coffee filter. The other half of water was used to dissolve bisulfate. These two solutions were mixed just prior to bleaching the film and were mixed with deionised water. This bleach needs a metabisulfite clearing bath and is one shot.

Gerald C Koch · Oct 9, 2017

After much wailing and gnashing of teeth it comes down to three choices. Switch to the dichromate bleach, use another film or try a prehardening bath.

As far as the copper sulfate bleaches they are far worse than the permanganate one. I used the copper bleach once with an Ansco film. I noticed almost immediate that the emulsion was frilling along the edges. At the end of the bleaching the emulsion slid right off the base.

lantau · Oct 11, 2017

Gerald C Koch said:
Thirty five percent hydrogen peroxide is a very dangerous chemical. Contact with organic materials can cause explosions. Many rocket designs were powered by kerosene and 35% peroxide. The average person would have difficulty obtaining it. Even if you could find it there would be a stiff hazmat charge. The highest concentration of peroxide available over the counter is 6% used as a hair bleach.

Because the world is full of terrorists and because our politicians watched too many episodes of Macgyver there is a legal limit within the EU that bans not only sale but also possession of H2O2 at concentrations >12% for ordinary private people. It came into force a few years ago and the transition time for possession of old stock is over. There is a possibility to get up to 35% using a registration regime, but I don't know what the requirements are for private persons. There are not that many substances that are restricted in such a strict way. The others are a few (per)chlorates, nitromethan and nitric acid. Each having a concentration limit.

So anyone in Europe should be aware of the, IMHO, unusual ban on possession, just in case someone with access kindly offers you a bottle of the good stuff.

studiocarter · Oct 11, 2017

Anon Ymous said:
I assume that Tri-X 7266 reversal film is not the ordinary 400TX, but I've successfully bleached 400TX using a permanganate bleach. I used half the amount of permanganate (1g/l) and 55g/l sodium bisulfate. Permanganate was dissolved in advance in half the volume of water needed and filtered with a coffee filter. The other half of water was used to dissolve bisulfate. These two solutions were mixed just prior to bleaching the film and were mixed with deionised water. This bleach needs a metabisulfite clearing bath and is one shot.

It is 200 daylight and 160 tungsten 16mm movie film. Sounds like I need to try it out. Thanks.

Gerald C Koch · Oct 11, 2017

The reason for the EU ban is that 35% peroxide is used to make trii-aceton triperoxide (TATP) a powerful explosive. There is a scene in one of the Terminator films where Sarh Conor's future husband comes back with supplies from the bigbox store. Among them are bottles of hydrogen peroxide. The EU regulation bans possession of hydrogen peroxide in strengths greater than 12%. As with many things the EU gets it wrong, 12% is just a capable of making TATP as the 35% version. Doesn't anyone in government consult an expert before enacting a law?

pepo007 · Oct 13, 2017

Regarding emulsion coming down, specifically Ilford PANF 50 was always bad guy, I read article that if you store film in freezer and trying process reversal, emulsion will go down, at least for Ilford Delta 100 and PANF. So I brought fresh batch and on PANF I got the same result. So kind of give up on it. If I will use pre-hardener, what formula should I use? I know about post-hardering (fixer) but about "pre" , that is new for me....

Photo Engineer · Oct 13, 2017

There are two types, one using formaldehyde and the other using chrome alum.

Chrome alum 5% in water, soak film for 5 minutes at 20C then wash 5 minutes, and then develop.

Formalin 37%, 5 - 10 ml, 50 g Sodium Carbonate, 50 - 100 g /l Sodium Sulfate (NOT Sulfite), and pH at 10. Treat film for 5 minutes at 20 C, wash 5 minutes and then develop.

PE

studiocarter · Oct 14, 2017

I reversed Foma R100 regular 8mm using the Foma reversal kit successfully, but at the time did not take note of the color of the bleach. It may have been purple. It was not orange. Could it be made with permangate? If so, it worked just fine, so, it CAN work.

Anon Ymous · Oct 14, 2017

Foma's reversal kit has a sulfuric acid and permanganate bleach according to the mods.

Soft emulsion from permanganate B&W reversal

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