Contrast control: bleaching prints before development

Some time ago I saw a thread, either her or on the large format photography forum, about bleaching prints before they went into the deveoper to help control extreme contrast. I can't remember where I saw it, so if anyone does, please point it out to me. I need to try it before telling the photography students where I work.
Thanks
Mike

Mike, I think that technique is in Mr. Rudmann's book The master's printing course I believe the title is. If you have it, give it a browse. My copy is on loan and I haven't tried it but I'm pretty sure it's in there.
regards
Erik

I can't see what bleaching would do before development. Is this photographic bleach or chlorine you're referring to? I have known chlorine to be fairly effective in reducing contrast in color prints. right about to zero i'd say.

Try it. Can't hurt.

From what I remember, it allows the shadow detail to fully develop without blowing out the highlights in very contrasty negs
Mike

Hi, here is the link to latent image bleaching:
http://unblinkingeye.com/Articles/LatentImageBleach/latentimagebleach.html

Jon

Yes. TR says it was used to downgrade graded paper. He calls this 'contrawise' bleaching. Quote: "When used on the formed image, ferri acts as a bleach, attacking highlights first, then the other tones. But when used on the latent image it does the opposite...". He says he's done it on multigrade as well, and says that in either case, potassium ferricyanide diluted to as little as 0.001%.

Selective Latent Image Manipulation Technique

tiberiustibz said:

I can't see what bleaching would do
before development.

Click to expand...

Or SLIMT. Search this NG for more info. The
article already pointed to at unblinkingeye
details well.

A EXTREMELY dilute solution is used after
exposure but before development. Cuts what
otherwise would be overly dense areas so
allowing highlight print down. Dan

Jon, Thank you for the link. I knew I'd seen it somewhere, but couldn't remember where.
Mike

It works for B&W negs as well.

vaughn

It's called the Sterry process and can be carried out before exposure, greater contrast reduction can be obtained using a Potassium Dichromate bleach.

Ian

The great thing about latent image bleaching, is that the highlights retain their high contrast sparkle (or very close to it), whilst the contrast in the midtones and shadows is reduced.

snallan said:

latent image bleaching ... the contrast in ... shadows is reduced.

Click to expand...

Shot to hell, I'd say...

I found it very hard to control.

The very dilute 0.01% ferri solution doesn't last more than a few minutes. I made up new bleach for each print. A transfer pipette is useful - I dispensed a 0.5 ml of 10% stock in 0.5 liter of water just before use.

It is an easy technique to play around with and good for getting rid of a rainy Sunday afternoon.

Here's David Kachel's take on it, where he calls it the New Sterry Method (for paper) and SLIMT (for negatives).

http://web.archive.org/web/20070205141750/www.codemastersworkshop.com/frontdoor/nw_strry.htm

I've never used it for paper, but it's a wonderful technique for negatives.

Murray

Nicholas Lindan said:

Shot to hell, I'd say...

I found it very hard to control.

The very dilute 0.01% ferri solution doesn't last more than a few minutes. I made up new bleach for each print. A transfer pipette is useful - I dispensed a 0.5 ml of 10% stock in 0.5 liter of water just before use.

It is an easy technique to play around with and good for getting rid of a rainy Sunday afternoon.

Click to expand...

On the contrary, if I have needed to use it, I have found it a reproducible technique. But, I have been using LIB with a restricted range of papers (Ilford and Kentmere), I know Tim Rudman in his book on darkroom techniques says some papers are prone to streaking or splotching.

I prepare a 0.1% stock solution (which is pretty stable stored in dark brown glass bottles), I then use this for preparing my latent image bleaches, and use from 5ml - 20ml of this stock per litre for my working bleach (i.e. between 5 and 20 times more dilute than with your trials). The working solution I use once, and then discard. During the bleaching I agitate gently, and continuously.

For this image (there was a url link here which no longer exists)(part of the "Let's all print one negative" thread) I wanted to print at grade 4 to keep the sparkle in the snows highlights, but from my trial contacts of the negative, I knew anything much above grade 2½ made the river very dark. To get the effect I required with latent image bleaching needed three small trial prints. I started with 10ml/l for one minute - too strong an effect, so I went to 5ml/l for one minute - too little of an effect, then tried 5ml/l for two minutes which gave me the effect I required. For the final prints I used the 5ml/l bath for two minutes, and got the same effect. This was on Ilford MG FB Warmtone.

Other papers do behave differently when bleaching the latent image; some may require continuous, vigorous agitation; others may prove unuseable. It is definitely not a one size fits all technique, and must be tested for the papers you use.

snallan said:

(there was a url link here which no longer exists)

Click to expand...

Very nice, maybe I will give it another go. All I got was too much, too little and WTF!? It took a while for me to realize how quickly the ferri went off. IIRC, capacity was around one 8x10 print per 500ml.

Nicholas Lindan said:

Very nice, maybe I will give it another go. All I got was too much, too little and WTF!? It took a while for me to realize how quickly the ferri went off. IIRC, capacity was around one 8x10 print per 500ml.

Click to expand...

Yes, the bleaching bath does seem to have the life expectancy of a gnat in a blast furnace. Mind, it is practically pure water!

snallan said:

Yes, the bleaching bath does seem to have the
life expectancy of a gnat in a blast furnace.
Mind, it is practically pure water!

Click to expand...

Practically pure? Is that good enough? Ferricyanide
is an oxidizer. As little as is used a trace of organic
or other oxidizable material will kill it. I'm about
to give the technique a go and will use distilled
and store in amber glass boston rounds. Dan

Ian Grant said:

It's called the Sterry process and can be carried out
before exposure, greater contrast reduction can be
obtained using a Potassium Dichromate bleach.Ian

Click to expand...

Much more recent is David Katchel's work and his
introduction of Potassium Ferricyanide as bleach.
He seems to have dropped out of site. No more
Front Door.

www.unblinkingeye.com will have to do. Dan

Thankyou all for your help and information. I'll be trying this out next time I'm in the darkroom
cheers
Mike

dancqu said:

Practically pure? Is that good enough? Ferricyanide
is an oxidizer. As little as is used a trace of organic
or other oxidizable material will kill it. I'm about
to give the technique a go and will use distilled
and store in amber glass boston rounds. Dan

Click to expand...

That is what I was suggesting. At 10 ml/l of my LIB stock, there is only 10mg of potassium ferricyanide in the bleach bath, in other words the bath is 99.999% water

dancqu said:

Practically pure? Is that good enough? .... will use distilled and store in amber glass boston rounds. Dan

Click to expand...

That's probably another of the reasons I found it intractable - the organic load in Cleveland water is very variable - and I don't remember using distilled water.

I don't think it can be stored. I found it had to be mixed just before use - right then and there.

For the 50 mg of ferri in it isn't expensive to dump. A teaspoon of ferri at 0.01% will make 50 liters. The distilled water would be the expensive part - oh, what the heck it's 10 cents a pint for distilled, that's a third or less the cost of a sheet of paper.

dancqu said:

Much more recent is David Katchel's work and his
introduction of Potassium Ferricyanide as bleach.
He seems to have dropped out of site. No more
Front Door.

Click to expand...

Pssst...look at post #13 on the previous page

edit: (easier for you) (there was a url link here which no longer exists)

Murray

P.S. The article has a link for SLIMT as well.

MurrayMinchin said:

Pssst...look at post #13 on the previous page

edit: (easier for you) (there was a url link here which no longer exists)

Murray

P.S. The article has a link for SLIMT as well.

Click to expand...

Yup, that's what I do. Though I came to it indirectly via Tim Rudman.

snallan said:

That is what I was suggesting. At 10 ml/l of my LIB stock, there is only 10mg of potassium ferricyanide in the bleach bath, in other words the bath is 99.999% water

Click to expand...

DOH!!! I meant there os only 1mg of the pot ferri!

Serves me right, typing when I should have been sleeping!

I first saw it in Darkroom...Techniques. I tried it. The print had to be exposed much longer. I had another technique that I compared with it which worked as well and was much easier to use. I have an easel spotmeter (my own design) with which, once calibrated, I can set the Zone at any part of the projected image that will show after the print is developed. I use it typically to check the ends of the scale. If I find that the scale of the negative image does not match the scale of the printing paper at hand, I will set the exposure for the highlight using the enlarger to control time and intensity. The other half of my equipment is a very dim, diffused, controllable flood lamp. With the negative still in place, I flood the image with uniform light and adjust it until the shadow exposure is just equal to that required for Zone 1. This does not, as you might think, add a uniform density to the printing exposure. In fact, I can measure the resulting highlight exposure and find that it has not significantly changed. The result of this method was not measurably different from the successful applications of the bleaching method, and a lot easier to control and predict.

How is it possible? Only because exposure is a logarithmic business. You will see the same effect on film in a camera with a pinhole in the bellows--loss of contrast. If you really analyze it, you will see that uniform exposure to add density to underexposed shadows degrades the image no more than subtracting halide uniformly to reduce overexposed shadows.