How to mix Benzotriazole

[simgrant]

When you dissolve BZT in IPA how long can you expect it to keep in solution?

 

[Truzi]

I'm way out of my league commenting on this thread, but I think I remember a thread about bleaching-back a print to help ameliorate the fog. I think David Lyga may have suggested it.

 

[simgrant]

I have bleached back fogged papers for this reason and also to alter the look of the paper after toning. It works but greatly increases highlight separations, which may or may not be a look you want. Once you bleach and fix the paper reacts differently in selenium toner, giving a warmer tone.

FWIW I have also tried BZT in fogged paper and have not found it to be useful. I found if I developed long enough to get even development in the shadows with good density then fogging would happen anyway. If I reduced development I got weak and uneven shadows, where I could see the mark left by my tongs in the shadows. I only use the fogged paper for experiments or unusual toning effects.

Regards, Simon.

 

[David Lyga]

Yes, Truzi.

You might find that for SERIOUSLY age-fogged paper it is best to do what you can with the restrainer (either benzotrazole or potassium bromide) and then, after fixation, to run the print through a mild dilution of Farmer's Reducer. To do this it is best to have overexposed your print slightly so that your print density is sufficient to withstand the dunking in the Farmer's Reducer long enough to attain brilliant hightlights. This also slightly increases print contrast.

This 'double approach' does wonders to revive age-fogged paper. - David Lyga

 

[bence8810]

David - thank you!
If you live in a place where Farmer's reducer isn't available on the shelves what would you do? I think I can get pretty much all the chemicals to mix my own.

Thanks,
Ben

 

[David Lyga]

Just get potassium ferricyanide. Even B&H sells it as it is both very common and VERY useful. There is a reason that Farmer's Reducer is called 'liquid gold' by old time photographers.

I make my reducer as follows: First make the bleach: (I use volume, not mass): 3 mL of potassium ferricyanide in water to make 100 mL of bleach.

For fixer, use fresh film strength fixer.

Now mix two parts bleach plus one part fixer to make a very strong reducer. You can dilute this mixture up to about 20 times (!) (to make the reduction less and less fast acting.) Test, using accurate measurements. Mixed together, the mixture's life is short: anywhere from 15 minutes to one hour or longer for the higher dilutions. But, alone, the bleach lasts forever and the fixer lasts months, if not years.

The reason that Farmer's Reducer acts to slightly INCREASE print contrast is because the lower densities (shadow detail and paper fog) are attacked more than the darker densities are. That is why it becomes necessary to somewhat increase the shadow density on the paper so that that density will not be obliterated when the fog is. Farmer's Reducer cannot tell the difference between unwanted density (fog) and wanted density (shadow detail).

Somebody in Tokyo has to sell standard darkroom chemicals. - David Lyga

 

[RattyMouse]

Somebody in Tokyo has to sell standard darkroom chemicals. - David Lyga

Yodobashi sells all kinds of darkroom chemicals.

 

[bence8810]

I make my reducer as follows: First make the bleach: (I use volume, not mass): 3 mL of potassium ferricyanide in water to make 100 mL of bleach.


For fixer, use fresh film strength fixer.


Now mix two parts bleach plus one part fixer to make a very strong reducer. You can dilute this mixture up to about 20 times (!) (to make the reduction less and less fast acting.) Test, using accurate measurements. Mixed together, the mixture's life is short: anywhere from 15 minutes to one hour or longer for the higher dilutions. But, alone, the bleach lasts forever and the fixer lasts months, if not years.
a

Thank you David!
I managed to find the Potassium Ferricyanide locally.
I don't have a measuring vehicle to measure 3ml's of the powder, would I be okay with 3 gramms instead? Water is easy to measure.


If you mix it with Fixer 2:1 like you say above I won't have to refix the print just like it would be with the Farmer's Reducer?
I read that if a print is bleached with Potassium Ferricyanide it needs to be refixed as the Silver is re-activated.


If bleaching an already dried print I should just soak it for a while in water before attempting to bleach?


And finally - can RC and FB both be bleached or it only works for FB?


Thanks,
Ben

 

[Anon Ymous]

Ben, farmer's reducer removes metallic silver from any medium, be it prints (FB/RC) or films. There's also another kind of bleach, the rehalogenating bleach, which converts metallic silver to a silver halide salt. These are the same photosensitive salts used in films - papers. When using these bleaches a second step is needed. The print (or film) can be either fixed (practically equivalent to what farmer's reducer does), or redeveloped. It is a reversible process, unlike the one mentioned by David. Redevelopment can either be done by a typical developer, or by other chemicals, like sodium sulfide. That's the way indirect sepia toners work. If you wish to make a rehalogenating bleach you will typically use potassium bromide with potassium ferricyanide.

Oh, and a presoaking the print before bleaching (or toning) is a good idea, as it will ensure uniformity.

 

[bence8810]

Anon, this was very educational, thank you.

So I guess if I mix the Potassium Ferricyanide into water and use it I'll have to fix at the end. If I use what David mentions (2/3rd Potassium Ferricyanide and water mix + 1/3rd Fixer) I can just wash the bleached print and be done with it?

I am also thinking about bleaching some prints at a particular place (white of the eyes etc) and for that I read the straight bleach is better (without the fixer part) so perhaps that's the way I'll go at first and see where I get.

There's so much to learn!
Ben

 

[David Lyga]

bence: either RC or FB is fine with this procedure.

With potassium ferricyanide one gram equals one mL. That is not the case for different chemicals but grams are equal to mL with potassium ferricyanide.

You take one part of film strength fixer solution and add it to two parts of the bleach. THAT will reduce but it might be too strong. If you want a slower reduction, simply add water (up to twenty times as much if you want VERY VERY slow reduction.) Experiment. Since you are adding fixer to the bleach NO re-fix is required.

You do not have to resoak a dry print, but it might help to even out the reduction if you use a stong reducer.

Anonymous is correct with bleaching ONLY being able to allow the print to be re-developed. But with adding fixer to the bleach you eliminate that altermative and get a direct reduction that is NOT reversable. That is why you have to watch your print carefully and stop just BEFORE it is as you want it to be.) Have a tray of water handy for stopping this reduction.) You can always resume the reduction process.

I want three yen for my trouble. - David Lyga

 

[MattKing]

I am a cautious sort. I would recommend that you refix the print . Just in case your reducing solution isn't completely uniform.

 

[Photo Engineer]

David, g=ml is only approximately true and then only if you grind the material to a fine powder. Potassium Ferricyanide comes in a variety of crystal forms including chunks larger than 1 ml in size (1 cc actually for a solid measure).

PE

 

[Gerald C Koch]

What David describes is called Farmer's reducer. This reducer is usually mixed up by color anywhere from a pale yellow to a darker yellow. This is what old-time photographers did. Speed of reduction is controlled by concentration of the ferricyanide. Therefore the darker the solution the faster the reduction. Experiment a bit with reject prints or old film. After a bit of practice it becomes very easy. Farmer's reducer can be use either with the ferricyanide and thiosulfate mixed together or used sequentially with the ferricyanide used first. Once the two are mixed together the life of the solution is rather short.

 

[bence8810]

Thank you all!

David - 3 yen over to you - a very good investment on my end.

I think I am getting a handle on this thing slowly.

One more question about the life of the solution.
You say if I mix it with the Fixer, the solution will expire soon (up to an hour or so)

If I leave the bleach pure as in NO fixer mixed in, how long can I keep it?
I was thinking of trying to mix up the 3% bleach and then diluting it down to a pale yellow to give me a weaker solution and keep it like this. Once I start bleaching - can I recycle this diluted solution and use later? Or I am better off mixing the 3% strong bleach and always only dilute as much as I need for a session and then discard?

The reason I am asking is that I have a large stash of fogged paper I want to use this on. Some are 20x24 so they'll take 2Liters at least at a time. If I make one print and then bleach it, I don't want to throw all that solution unless it is absolutely necessary.

Thanks a lot,
Ben

 

[David Lyga]

David, g=ml is only approximately true and then only if you grind the material to a fine powder. Potassium Ferricyanide comes in a variety of crystal forms including chunks larger than 1 ml in size (1 cc actually for a solid measure).

PE

Very interesting, PE, as I was not aware of this difference. The ONLY potassium ferrycyanide I have ever acquired was that of the standard 'powder'.

Of couse you are correct in stating that there is no substitute for mass measurements when accuracy is vital, but when with such measuring that need not be so perfect, as is the case with Farmer's Reducer, my 'error' is certainly within acceptable bounds. - David Lyga

 

[David Lyga]

Again, 'alone' the bleach lasts forever (just don't store is so it is always in sunlight).
Best to do these things 'one shot' so there is no possiblity of contamination. Leave the original bleach at 3% and dilute a specific amount of the fix/bleach as needed. You will probably modify my recommendations a bit when you see how things work for you. Water changed the quickness of the reduction process. Don't change the ORIGINAL stock solutions or you will get so confused that I will have to up my fee to FIVE YEN in order to set you back onto the right road.

Save your bleaching for ALL the prints at one session, after they ALL have been fixed. No need to waste. Understand that doing 20 X 24 is going to require a yeoman's effort to get consistency. You will learn new curse words in the process, I promise you.

Just remember that you must know, in advance, how much density you must have in that print before you go wasting all your chemicals. Test with small prints and small mixtures of what I said. Become, first, a 'pro'. You will find that that extra density I said to have in your print will be needed once that reduction process proceeds. - David Lyga

Thank you all!

David - 3 yen over to you - a very good investment on my end.

I think I am getting a handle on this thing slowly.

One more question about the life of the solution.
You say if I mix it with the Fixer, the solution will expire soon (up to an hour or so)

If I leave the bleach pure as in NO fixer mixed in, how long can I keep it?
I was thinking of trying to mix up the 3% bleach and then diluting it down to a pale yellow to give me a weaker solution and keep it like this. Once I start bleaching - can I recycle this diluted solution and use later? Or I am better off mixing the 3% strong bleach and always only dilute as much as I need for a session and then discard?

The reason I am asking is that I have a large stash of fogged paper I want to use this on. Some are 20x24 so they'll take 2Liters at least at a time. If I make one print and then bleach it, I don't want to throw all that solution unless it is absolutely necessary.

Thanks a lot,
Ben

 

[bence8810]

David - thank you for your valuable post. Really much appreciated.
Tomorrow I'll buy the chemical and will try bleaching this weekend.

I have tested the BZAT solution I had originally trouble with yesterday and got some surprisingly good results.

The paper is Forte Bromofort BN-4 which was a normal grade paper (3). This pack is from the early 90's. I've printed the below shot in normal developer (top photo) and then with 30ml of 2% solution added per liter (bottom photo)
For the BZAT development I had to expose a little longer (7sec as opposed to 4sec) and developed for 2 minutes both. The BZAT paper started showing the image around the 1minute mark whereas the straight developer started at 20seconds.

You tell me what you think, I can see a contrast increase while the boy remains more or less the same on both image. The negative is very contrasty, pushed Eastman 5222 @400 in Rodinal 1:50 for 11minutes.

Thanks,
Ben

Edit:

I then tried two more in the same BZAT developer.
Same as the 2nd photo but developing for 3 minutes which I thought was a little dark so for the next try I reduced exposure but kept the 3 minutes developing.

Top: f16 7sec / 180sec
Bottom: f16 6.5sec / 180sec

 

[David Lyga]

Of course, the lower pics show cleaner whites. (But I have to laugh: in the USA this picture might get you arrested!!!) - David Lyga

 

[bence8810]

That's my son - hope that makes it okay

So you think I am better of developing for 120sec or should go for 180 and expose less?

 

[David Lyga]

I am confused: the data you give says you developed both for 180 seconds. The real test is getting enough contrast. Even the top one could have been rectified with Farmer's Reducer as long as you had enough density to withstand the reduction.

Your paper is probably not that fogged, so you are flexible with what you do. But with VERY fogged paper (coin test reveals more than 50% density in unexposed area of coin) you are best advised to develop until that 50% is reached (in order to acquire as much contrast as is possible), and not beyond, because if you go much beyond that you will end up with a situation whereby the reduction will not leave anything left of the image: little differentiation as everything will be dark!!!) Structure your development so that it does not go BEYOND that 50% coin threshold. THAT determines how much you develop.

This is a bit strange to understand, perhaps, because with fresh paper you have no such threshold to worry about. But with age-fogged paper, you want as much contrast as you can get, so you want to develop as long as possible. But since contrast begins diminishing after you reach that 50% threshold, so you must hold back when that point has been reached.

Two more yen added to the tally. - David Lyga

 

[bence8810]

I am confused: the data you give says you developed both for 180 seconds. The real test is getting enough contrast. Even the top one could have been rectified with Farmer's Reducer as long as you had enough density to withstand the reduction.

Hi David,

I posted 2 photos each in the 2 submissions above - that's 4 sheets of paper.

From top to bottom:

1: Straight developer / f16 4sec / 120sec
2: BZAT added dev / f16 7sec / 120sec
3: BZAT added dev / f16 7sec / 180sec
4: BZAT added dev / f16 6.5sec / 180sec

You explained the coin test already in PM which I didn't fully understand so I keep reading it again and again.

Thanks,
Ben

 

[David Lyga]

You place a coin, held down firmly, so that THAT area is not exposed. THAT indicates whether the UNexposed paper is fogged after development. You TIME the development so that you want all the possible contrast, but WITHOUT, WITHOUT, WITHOUT, BEN, undue density on the coin area. If you send a few yen I will show you how those yen coins do the job!

Since your paper seems to not be so fogged, EITHER the 120 or 180 timing works for you, as you do attain adequate contrast. But if it WERE very fogged, the development timing WOULD make a difference in contrast achievement. -David Lyga

 

[bence8810]

You place a coin, held down firmly, so that THAT area is not exposed. THAT indicates whether the UNexposed paper is fogged after development. You TIME the development so that you want all the possible contrast, but WITHOUT, WITHOUT, WITHOUT, BEN, undue density on the coin area. If you send a few yen I will show you how those yen coins do the job!

Since your paper seems to not be so fogged, EITHER the 120 or 180 timing works for you, as you do attain adequate contrast. But if it WERE very fogged, the development timing WOULD make a difference in contrast achievement. -David Lyga

Hi David,

This is most interesting yet to every answer you give I have more questions. I'll end up owing you like 15 yen by the time we are done with this...

Really appreciate your time!
I perhaps scared the others away with my son's photo - can't edit it out anymore as the time for editing is up. APUG has some sort of limits.

Anyways, I'll try this coin test for sure. I sort of understand, I take a strip of paper I'd like to test or perhaps two, put a coin on each of them and turn the lights on for a few seconds. I then develop them, one for 120 seconds and the other one for 180.

The question is what am I going to be looking for? How to tell where's 50% density?
I assume if I have fog the paper developed shorter will show more difference between the exposed and unexposed areas than the one I developed longer?

I also feel this paper isn't badly fogged and that BZAT has already done a fine job in recovering it. However, I have a lot of older paper too so I'd like to get this fully understood. I can't get myself to throw paper away...

Slightly different thing - was there ever a FB paper by ilford that wasn't white based but cream? I have two boxes of 20x24's and it is sort of yellow not only on the emulsion side but the back of it too - so this tells me the yellowing I see isn't because of age but by default there.

Thanks,
Ben

 

[David Lyga]

First, about the photo: I have a 1942 Leica manual, the official version, that has a few pictures in it that would get me banned from APUG if I dared to scan them. We are living in a politically correct world that 'creates' danger out of little substance. Back in 1942 I PROMISE you that those kids in that manual did not get 'molested' because of their lack of full clothing. But by NOW 'creating' such danger we, in fact, PUT kids like those in danger. In fact, this affirmation just might get me in trouble with APUG. We will see. I will herald apug for not becoming terrified and deleting your son's pictures. I probably would not have posted them but, when all is said and done, this 'fear' is really augmented by political correctness rather than substance. There is no sex appeal toward your innocent son: in fact, I find German cockroaches a bit more enticing!

When you do the coin test do not be foolish and use a large piece of paper. Just use about one square inch. (People who waste paper are jerks.) HOLD the coin on the paper so light does not creep underneath. It can. You 'tell' 50% by using your brain: the halfway distance between white and black under that coin area, simple as that. You don't HAVE to attain 50% but that is your LIMIT.

Sometimes using Farmer's reducer to too much of an extent will impart a yellowing on the paper, even if it was not made with a cream base. The trick is to not HAVE to reduce too much. I assume your 'BZAT' is Benzotriazole stock solution? I told you that I also add a gram or two of baking soda: this seems to augment the reduction effect to my liking.

Do not throw paper away but, rather, use it to LEARN how to do this. This is not a lazy man's job: you do not have the luxury of it not really mattering how much the paper is developed like you do with fresh paper. Just remember that with age-fogged paper, before you even make an exposure, you MUST determine how much that paper can withstand development. THAT has to be determined first, not later, After that maximum development time has been determined, you now KNOW that you have to conform your exposure to fit into this paradigm: and this paradigm is to develop it as much as the 50% threshold or, in the case of not so fogged paper, even less so that you have less reducing to do. It is a bit like reverse engineering (but don't ever attempt that with David Lyga's feeble brain!)

Don't start with large prints: you will become dismayed by having to police two events at one time (and, doing so, without a gun!). LEARN how to deal with age-fogged materials first, then deal with the 'MAC trucks'.

You have learned when I come online: it is probably close to midnite now in the Tokyo area, when it is 9 AM in Philadelphia. - David Lyga