Question on Paper Image Latency

[Mackinaw]

I don't always have time for a full-blown darkroom session, meaning trays and such, and, at times, use a daylight drum to process my prints. This has always worked well and I've always gotten good results, until now. This morning, I didn't have time to both expose and process the paper (Ilford Multigrade RC Warmtone) so I exposed a sheet of paper and stuck it in the drum. I ended up processing the paper about 5 hours later and, to my amazement, when I removed the paper from the drum, the image was so faint I could barely see it. I immediately exposed and processed another sheet of paper and the print came out great. All I can figure is that this paper (which I really like) has a very short latent image and should be processed ASAP.

Is this unusual? I've done the exact same thing (expose and develop later) with other papers, specifically Forte Polygrade V RC, with good results, sometimes waiting as long as ten hours before processing.

Just curious if other folks have seen this.

Jim Bielecki

 

[RalphLambrecht]

This is not uncommon. Actually, with some papers, the resulting density goes up at first (within a few minutes) and then drops. The chemical reaction is known and well explained but too involved for me to post here. Basically, the exposure creates a vulnerable change in the silver halides, if not developed soon, it fades away. The only company, I know of, publishing this data was Agfa. This is very critical with test strips. A precise test strip must have a consistent time from exposure to development. Paper should be developed within minutes of exposure, or at least with a constant 'waiting' time to get constant results. I measured density changes of up to 0.1 within 10 minutes of variation.

 

[Photo Engineer]

Having such poor latent image keeping as you describe is unusual to say the least.

If you have a lot of prints to make, say 100 or so, you may expose them in one session and then process them in another lasthing quite a while as you develop individual prints. Therefore, the LIK should be quite good over several hours.

Photofinishers often do 100 - 200 ft rolls of prints and then process them. On such a roll, the first print may be an hour to several hours older than the last print made. They should all match.

So, as I said, this is unusual. However, paper LIK is not as good as film LIK for the most part. Film LIK has to be stable over a year or so where paper LIK is stable over a day or so in general.

PE

 

[RalphLambrecht]

PE

Define 'They should all match'. What is the tolerance? My experience with Agfa, Ilford and Kodak papers is quite different. Even a 10 minute delay, causes measurable density differences. Yes, you need to have the prints next to each other to see it, but the differences are easy to measure.

 

[Photo Engineer]

IIRC, the Kodak LIK goal was to have identical prints from about the time it took to get from the printing station to the developer tray and a print made several hours earlier. This would be about 5" to 2 or 4 hours time for matching prints. I don't remember the longer time. It may have been 24 hours AAMOF. I have simply forgotten.

Photofinishers would often get orders for 100 or so prints, and it was a requirement that the starting and ending print be identical for either machine made prints or enlarger prints.

This included both contrast and speed effects with respect to LIK.

Having made hundreds of prints in a day and having basket processed them in a 3.5 gallon tank in batches of 25 - 50 sheets, and having printed sensitometry on each sheet, I can say that the B&W and color products I worked with had much less than a 0.1 log E change, probably on the order of 0.05 log E with no contrast effect evident. I would print for 4 hours and process after lunch in a normal day. My first print therefore would have 5 hours LIK and the last would have 1 hour. Sometimes I would print then process giving a total LIK of about 10" to 4 hours.

The B&W prints went through a Pako processor as rolls, the color went through a Calumet processor in 16x20 baskets holding 8x10 prints in a 4 part basket or an EK basket process holding 8x10 baskets.

I have not made this comparison since about 1970. Things change, but that was the goal then.

PE

 

[RalphLambrecht]

PE

'I can say that the B&W and color products I worked with had much less than a 0.1 log E change, probably on the order of 0.05 log E with no contrast effect evident.'

Did you measure and remember this, or are you guessing? My experience and measurements are quite different for the times you quoted, but I'm happy to repeat my test with current materials.

 

[Photo Engineer]

PE

'I can say that the B&W and color products I worked with had much less than a 0.1 log E change, probably on the order of 0.05 log E with no contrast effect evident.'

Did you measure and remember this, or are you guessing? My experience and measurements are quite different for the times you quoted, but I'm happy to repeat my test with current materials.

Ralph;

I have no Kodak data in my posession since I have retired.

I am doing the best I can to remember our aim specs and tests from over 30 years ago, but I can say this, that if a photofinisher made a long run and found the first print, done 2 hours earlier, underexposed by some obvious amount and the last print normally exposed, but just done about 2 minutes previously, there would be a huge outcry in the industry! I think you would agree.

A difference of about 0.05 log E is just noticeable IIRC in a run like that.

So, I am trying to remember data from years gone by and also to suggest that if there were such large changes in product, there would be an industry wide outcry from the photofinishers.

In all liklihood, people see more variation from temperature, exposure time, developer variations, agitation, voltage fluctuations and combinations of these than they do from LIK. I know that I have.

With B&W and color both, I use Jobo tanks with 4 - 5 prints. My average exposure is 12" and with setup time that means that I rarely have more than a 15 minute span from first to last print in a run currently. I have often made batches of 5 prints this way and see no difference over a few seconds LIK to 15 mins. This is hardly in the range of what I used to test for, so I cannot speak for current products, but I rely on the lack of huge complaints from the industry.

I'm completely open to reexamining the issue though if you really feel that it is needed. We can both run some tests.

PE

 

[RalphLambrecht]

PE

I remember having a similar conversation with Dave Valvo from Kodak a few years back, when he was making a set of prints for Photokina. Do you know him (or are you him)? I must say that my experience with poor image latency refers to former Ilford papers. At the time, they were confirmed by Mike Gristwood of Ilford. Maybe it is time to do a test again. It's easy enough to do. Let's agree on a design for the test, and you do it with one paper, and I do it for another.

 

[Photo Engineer]

PE

I remember having a similar conversation with Dave Valvo from Kodak a few years back, when he was making a set of prints for Photokina. Do you know him (or are you him)? I must say that my experience with poor image latency refers to former Ilford papers. At the time, they were confirmed by Mike Gristwood of Ilford. Maybe it is time to do a test again. It's easy enough to do. Let's agree on a design for the test, and you do it with one paper, and I do it for another.

I have heard the name Dave Valvo, but I don't know him, nor have I met him.

I am willing, but all I have right now is some Kenmere, Luminos (old) and MGIV.

I can actually run all 3 papers with no severe problem, and I might even have some old EK Polycontrast IV.

The test I have in mind is an exposure at about 7 PM on Day 1.

On day 2, an exposure at 6 PM, 6:30 PM 6:45 PM and 6:59 PM. Then process all 5 sheets. Something like that gives you 24 hour, 1 hour, 1/2 hour etc... LIK data. It may be that we would need one at 5 PM for 2 hour and etc. This is TBD. Open to your suggestions.

I would like to add that there has been a lot of work on LIK addenda for emulsions at EK, Ilford and other companies so that this kind of variation is minimized. Addenda are also there for raw stock keeping and reciprocity failure, and often the same ingredients control several things at once.

PE

 

[gainer]

I have no experience to share except that I have used bleaching of the latent image in some experiments to control contrast. It was not my idea, and I do not use it anymore, but I do remember how utterly weak a solution of ferricyanide can be and still bleach some of the latent image. What possibility might there be that an individual darkroom would have some atmospheric contaminant that would bleach the latent image without kiling the operator?

 

[Photo Engineer]

I have no experience to share except that I have used bleaching of the latent image in some experiments to control contrast. It was not my idea, and I do not use it anymore, but I do remember how utterly weak a solution of ferricyanide can be and still bleach some of the latent image. What possibility might there be that an individual darkroom would have some atmospheric contaminant that would bleach the latent image without kiling the operator?

Patrick;

What bleach that is a vapor do you have in mind?

I can't think of one offhand, but I'll give a try at coming up with one.

I can think of quite a few silver halide solvents that are gases.

PE

 

[RalphLambrecht]

I like the test proposal in general. Do it for Kentmere, I'll do it for MGIV.

Let's do 2m, 4m, 8m, 15m, 30m, 1h, 2h, 4h, 8h, 16h.

 

[Photo Engineer]

I like the test proposal in general. Do it for Kentmere, I'll do it for MGIV.

Let's do 2m, 4m, 8m, 15m, 30m, 1h, 2h, 4h, 8h, 16h.

Gee, with that timing, I would have to do math. Aaaagh.

Well, if you insist.

It will take me a bit to get going. I have a large keeping experiment going on at the present time, then I have my workshop. Be patient with me, please.

PE

 

[gainer]

Patrick;

What bleach that is a vapor do you have in mind?

I can't think of one offhand, but I'll give a try at coming up with one.

I can think of quite a few silver halide solvents that are gases.

PE

I probably should not have specified gaseous. There are plenty of contaminants that might be present due to faulty washing of utensils. It's pretty far fetched anyway on my part. It was just a thought about how it might be possible for you in a labaratory to have different experiences than some of us others.

I have heard that part of Kodak's research was to see how far one could get from ideal conditions and still get acceptable results. There can be random packaging errors, poor water and inaccurate measurements on the consumers end, and so on. But I digress. At any rate, when some unexpected behavior of photo chemicals or sensitive materials befalls me, the first thing to do is to repeat the procedure I thought I was using but more carefully. Sometimes what I thought I was doing was far from what I actually did, like pouring the wrong solution in the tank. Sometimes the procedure was correct but that particular sample of the film or paper was bad. What that means, of course, is that repetitions of the same conditions are sometimes more informative than a wider range of the same number of tests. I learned matrix algebra and least-squares curve fitting to do surveying, flight research and human factors research. Now I really have digressed. Good night.

 

[dancqu]

I probably should not have specified gaseous.

But I think you may have hit upon it!

At least two gases are somewhat common to
darkrooms; sulfur dioxide and ammonia. The later,
will be absorbed by the moisture in the emulsion
and complex with the chloride and to a lessor
extent the bromide of silver.

Considering the infinitesimal amount of ferricyanide
used in the SLIMT, I think it possible that enough
complexed latent image silver may generate to
cause some loss of image. Dan

 

[Photo Engineer]

But I think you may have hit upon it!

At least two gases are somewhat common to
darkrooms; sulfur dioxide and ammonia. The later,
will be absorbed by the moisture in the emulsion
and complex with the chloride and to a lessor
extent the bromide of silver.

Considering the infinitesimal amount of ferricyanide
used in the SLIMT, I think it possible that enough
complexed latent image silver may generate to
cause some loss of image. Dan

Dan;

Of these two gases, only the ammonia can really do any serious harm. It is usually not present in a high enough concentration to do any harm. It is used in making emulsions.

They both can actually, but sulfite has been used for years as a mild stabilzer in gelatin and it has been found that the emulsions resist any effect quite well.

PE

 

[gainer]

I can boil down what I said in my midnight haze. The sequence of times suggested by Ralph Lambrecht is too close together for my comfort. Take the end points first and do repetitions of each of them them rather than trying to get a curve shape by single instances of many storage times. What you learn from average and mean square deviations at the one storage time compared with the same statistics for the other may give different insights into the nature of the problem. And don't forget to compare the results using fresh developer with those using developer that was kept for the length of the storage period.
I am, of course, using my prerogative as a great grandfather to give this advice.

 

[Photo Engineer]

I can boil down what I said in my midnight haze. The sequence of times suggested by Ralph Lambrecht is too close together for my comfort. Take the end points first and do repetitions of each of them them rather than trying to get a curve shape by single instances of many storage times. What you learn from average and mean square deviations at the one storage time compared with the same statistics for the other may give different insights into the nature of the problem. And don't forget to compare the results using fresh developer with those using developer that was kept for the length of the storage period.
I am, of course, using my prerogative as a great grandfather to give this advice.

Patrick;

Since I am a grandfather as well, I feel qualified to comment.

In an LIK test, the object is to develop all different exposures at exactly the same time to simluate a real run by a professional.

As such, all of these prints will go through the same developer at the same time. The idea is to have enough developer so that first to last seasoning will not take place, or will be insignificant. Or, they can all run at the same time with interleafing agitation, a rather difficult task with 10 prints at one time, but not impossible.

As for when it will get done, I am 96 hours into a developer keeping test, and have quite a bit of time to go before I can do this test.

PE