Black and white reversal film, safer bleaching

fert

Member
Joined
Oct 2, 2023
Messages
36
Location
china
Format
35mm
name cas weights
60 per cent sulphuric acid
30ml
High cerium sulfate 13590-82-4 30g
ferrous sulfate 10028-22-5 20g
A total of 200 ml of concentrate is prepared, which can be diluted to 1 litre of working solution. The time is 3 to 5 minutes.
In the bleaching directly after the use of film stopping solution or sulfuric acid solution to clean, cleaning after the start of water washing, more water washing several times, to ensure that the cleaning is clean. Later you can start the second exposure and the second development.
 

DeletedAcct1

Member
Joined
Sep 24, 2020
Messages
869
Location
World
Format
35mm
halfaman said:
The problem with potassium permangante is its stability being so reactive. No major issues with safety compared with dichromates.
Click to expand...

If you store a potassium permanganate solution in bottle A and a sulfuric acid solution in bottle B I assure you that this configuration is stable even after 4 years. I'm currently using a Foma reversal kit that is two years overdue (and was manufactured in 2019 - I bought it before the pandemic) and the bleach works perfectly as of august 2024.
As an added precaution you can add 20gr per liter of sodium hexametaphosphate in bottle A.
 
OP
OP

fert

Member
Joined
Oct 2, 2023
Messages
36
Location
china
Format
35mm

I agree with you that potassium permanganate is safer, but he can't go to anticipate the damage to the negative, for example, bleaching in a certain amount of time after the bleaching is completed after picking up the negative to find out if there is any bleached clean black material on it, when you are bleaching again may be he bleached clean, but you will find that he has also caused damage to your negatives such as de-moulding. Potassium dichromate bleaching, he has a very good performance in a shorter period of time to complete the bleaching, and has a reinforcing effect on the negative. But it is very dangerous. In China both potassium permanganate and potassium dichromate belong to the tube products ordinary people can not get and sulfuric acid high cerium, belong to the general chemical supplies, including the above said sulfuric acid and iron sulfate, he can make the negative in three to five minutes to complete the bleaching has the performance of the bleaching of potassium dichromate, and will not cause damage to the negative, despite the time again, he will not go to the destruction of the negative. Please correct me if I am wrong about anything. I will listen to your comments carefully. Thank you very much for your reply.
 
  • fert
  • Deleted
OP
OP

fert

Member
Joined
Oct 2, 2023
Messages
36
Location
china
Format
35mm
halfaman said:
The only quotation I was able to find of Cerium (IV) sulfate is 50 € for 100 grams in tetrahydrated presentation. That makes this bleach quite expensive...
Click to expand...

This is something I did overlook, buying chemicals in the West can be a real headache.In China, the price of homocerium sulphate is 500 grams, 176 RMB.It's about 23 euros.Buying it from China and shipping it back home seems to have a whole lot of trouble waiting again.It seems to be a dead end.
 

DeletedAcct1

Member
Joined
Sep 24, 2020
Messages
869
Location
World
Format
35mm
I've found that using 4g per liter of potassium permanganate plus 55g sodium hydrogensulfate (NaHSO4) at precisely 18°C prevents all sorts of subbing layer damage, retaining a good bleaching acion. Add also 20gr per liter of sodium hexametaphosphate to prevent the MnO2 redeposition during bleaching. Store the permanganate plus the hexametaphosphate solution in bottle A and the hydrogensulfate solution in bottle B. Mix just before use 1:1 ratio.
Sodium hydrogensulfate being a powder is much safer than handling caustic concentrated sulfuric acid. Make sure that both permanganate and hydrogensulfate are reagent grade because any trace amount of chlorine iodine etc will interfer with bleaching action.
 
Last edited:
OP
OP

fert

Member
Joined
Oct 2, 2023
Messages
36
Location
china
Format
35mm

Regarding reagent-grade potassium permanganate, it is very frustrating that individuals in China can no longer purchase reagent-grade potassium permanganate, which has been placed under controlled substances.It seems that a lab at a university blew up because of improper handling of potassium permanganate.
 

DeletedAcct1

Member
Joined
Sep 24, 2020
Messages
869
Location
World
Format
35mm

You're dealing with chemicals and you oughta know how to safely handle them, no matter what you're using.
Study permanganate and its reactivity and all the substances it does not have to come in contact with.
Read carefully all the sds.
Using gloves certainly helps.
Keep your workbench clean, have a comfortable space where to work.
Chemistry is not dangerous if you know what to do and how to do it.
 

Romanko

Member
Joined
Sep 3, 2021
Messages
889
Location
Sydney, Australia
Format
Medium Format
fert said:
it is very frustrating that individuals in China can no longer purchase reagent-grade potassium permanganate
Click to expand...
Not only in China but in most of the world. Potassium permanganate is a precursor in the manufacturing of a common drug. You might be able to legally obtain it in small concentrations from a pharmacy. There are other options but I'd rather not discuss them here.
 

koraks

Moderator
Moderator
Joined
Nov 29, 2018
Messages
23,516
Location
Europe
Format
Multi Format
Romanko said:
You might be able to legally obtain it in small concentrations from a pharmacy.
Click to expand...

Potassium permanganate is used to treat infections in koi. I've come across koi pond suppliers who sell small quantities of permanganate, no questions asked. Prices seemed reasonable for small quantities, although I didn't bother and just filled in the declaration required around here to buy larger quantities. I think it does require a business registration though.
 

Ausar

Member
Joined
Oct 12, 2024
Messages
18
Location
China
Format
35mm
Did you test if it will damage the film?

like, bleaching for 10min or 20min, and see if the film still lives?
 

DeletedAcct1

Member
Joined
Sep 24, 2020
Messages
869
Location
World
Format
35mm
Ausar said:
Did you test if it will damage the film?

like, bleaching for 10min or 20min, and see if the film still lives?
Click to expand...

There's absolutely no need to bleach for that long. Neither with Foma 100 R which does have a stubborn Ag "rem-jet like" layer that can be removed only in the bleach...
Some supplier of permanganate:

POTASSIO PERMANGANATO Ph.Eur. 0,25 kg, Farmaceutici Labotech2000

POTASSIO PERMANGANATO Ph.Eur. 0,25 kg, Farmaceutici
www.labotech2000.it
Suvatlar
 

Ausar

Member
Joined
Oct 12, 2024
Messages
18
Location
China
Format
35mm

I can get KMnO4, I just want to know if this bleach will damage the film easily, like KMnO4 do if you over-bleach for just a few min
 

DeletedAcct1

Member
Joined
Sep 24, 2020
Messages
869
Location
World
Format
35mm
Ausar said:
I can get KMnO4, I just want to know if this bleach will damage the film easily, like KMnO4 do if you over-bleach for just a few min
Click to expand...

If you use it at 18°C for max 5 minutes it won't harm the film. Halve the Ilford suggested concentration
8 minutes max for Foma 100 R.

Bottle A:
potassium permanganate 2g
sodium hexametaphosphate 20gr
water to 500ml

Bottle B:
55,6g sodium hydrogensulfate

Mix 1:1 just before use and then discard.
 

lamerko

Member
Joined
Oct 27, 2022
Messages
759
Location
Bulgaria
Format
Multi Format
Until recently, I thought it was impossible to order potassium permanganate in Bulgaria. It turned out that it is actually quite affordable - in pharmacies and agrarian stores it is available in sizes from 5 to 100 grams. And quite cheap. It seems to be widely used in agriculture and animal husbandry, so it is available in stores with such a focus. The interesting thing is that there are two formulas printed on the packages, but with one CAS number. One is the familiar KMnO4, and the other - HMnO4.K. It seems to be about the same thing. The bigger problem is hydrogen sulfate - it's cheap, but in 20 kg bags. I'm not too sure if I'll be able to beg a small amount.
 
OP
OP

fert

Member
Joined
Oct 2, 2023
Messages
36
Location
china
Format
35mm
We certainly know the safety of potassium permanganate, but because of his unstable play, we can not help but look for other methods, compared to potassium dichromate, toxicity is too large, hydrogen peroxide will produce high temperatures, need to be properly handled, high cerium sulphate is also in a website to see, in the beginning of the processing speed is relatively slow, you need to soak for more than 10 minutes, and now can be achieved within 5 minutes.But the raw materials are again more expensive compared to others.Black and white bleaching shows an impossible triangular situation.There may be better solutions in the future.
 

DeletedAcct1

Member
Joined
Sep 24, 2020
Messages
869
Location
World
Format
35mm

No, there isn't any alternative to a permanganate bleach, otherwise don't you think that Adox and Foma would have implemented it?
 

Donald Qualls

Subscriber
Joined
Jan 19, 2005
Messages
12,326
Location
North Carolina
Format
Multi Format
Alessandro Serrao said:
No, there isn't any alternative to a permanganate bleach, otherwise don't you think that Adox and Foma would have implemented it?
Click to expand...

Well, there is, and it was used for decades before permanganate became the common method, but dichromate bleach is very much not going to fly in the EU (hexavalent chromium, last I heard was completely banned). I can still buy the stuff in the USA, but given it's a known carcinogen, I'd prefer another method.

I still want to try a (dilute) nitric acid bleach; if I can convert the developed silver directly to silver nitrate, it'll come out clean as it does with dichromate bleach. Even if it's slower, that's a plus.
 

DeletedAcct1

Member
Joined
Sep 24, 2020
Messages
869
Location
World
Format
35mm

Historically permanganate bleach was the first bleach to be discovered by an italian chemist, professor Roberto Namias at the very beginning of the 1900.
It wasn't dichromate the first bleach used and it's not an alternative in most parts of the world anymore.
  • Namias, Roberto, “Reversed Negatives”, British Journal of Photography, 47, 679 (1900).
  • https://unblinkingeye.com/Articles/PBR/pbr.html

  • History

    The PBR story resembles a detective novel, in which clues are provided at various intervals in the tale. The use of permanganate bleach was first reported by Namias in 1900, in conjunction with an oxalic acid clearing bath, in the first practical process for reversal of a negative photographic image to a positive one. In essence, the film was first developed to a silver negative image, the silver removed by bleaching, excess permanganate and manganese dioxide removed with an oxalic acid clearing bath, followed by a second exposure to light, and second development of the remaining silver halide to a positive image. It became the basis for the Lumiere Autochrome technique, the first practical color diapositive process, and its Dufaycolor successor. John G. Capstaff of Kodak, in US Patent 1,460,703, was apparently the first to report PBR in connection with the original technique for processing amateur black-and-white motion picture prints by reversal. Following permanganate bleaching of the exposed and developed negative, and clearing with sodium bisulfite, the film was submitted to a controlled diffused light second exposure to correct for errors in the first exposure, given second development, and fixed in hypo, resulting in a positive suitable for projection. Capstaff reported that if the film was initially underexposed, and given a limited second exposure, re-reversal often occurred, leading to low, rather than expected high density shadows. However, when a small amount of silver nitrate was added to the bleach, or a light fogged leader strip of film initially bleached, or if the film was initially bathed in dilute sodium hydroxide, re-reversal was prevented (Capstaff 1926, Kodak 1926). It was speculated that added silver ion precipitated traces of chloride ion present in tap water used to prepare bleach solution, and that chloride ion was somehow the culprit. In this regard, Glafkides indicated that tap water for photographic solutions often contains 10-50 mg/l of chloride ion. Similarly, bromide content for a variety of US water facilities averages around 50 mg/l (Amy).

I can't stress more the use of all reagent-grade chemistry and distilled (perferably double-distilled) water because of the risk of chlorine presence also in trace amout that will increase the risk of permanganate bleach re-reversal effect.
 
Last edited:
You must log in or register to reply here.
Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…