Any Hard Data On Silver Quantity?

[gainer]

Let me get this straight. I NEVER said that original silver content, before exposure and development, had any bearing on the density of the developed image except to limit the maximum attainable density. The developer used does have a bearing, no matter what the silver content is. Further, the developer can impose its own limit on maximum density by removing silver during the development process.

The man was looking for information on silver content for one reason or another. The photometric equivalent has a bearing on the amount of silver contained in exposed, developed and fixed black and white film. Whatever was in it before exposure, development and fixation has no bearing on how much is in it now. Neither does the process by which the density came to be. I quoted the photometric equivalent found by Hurter and Driffield, and the statement of Hardy and Perrin at a later date. I made no pronouncement of infallibility. If we know the actual photometric equivalent of silver and the average density of the film whose silver we want to recover, we can get a pretty good estimate of the amount of silver we can recover per unit area of the film. No matter what we think we know, we will not have precise knowledge until the processing to recover the silver is completed.

If the relationship between maximum density and silver content in the final image is not fixed for any given sensitive material, positive or negative, given the same processing, then we have no basis for charts of contrast vs time and temperature of development. I am restating this fact in different terms so you will be able to grasp my reasoning. I am not stupid, nor has anyone who knows me implied that I am. I have written technical reports for NACA-NASA and have served as chairman of editorial committees for others. I have presented technical papers at manual control conferences.

You will forgive me, I hope, for not looking up what Ron Mowery has to say about this. He has a penchant for contradicting anything he thinks I said.

 

[Ed Sukach]

Hi Ed

regarding the value of a silver recovery unit, In one 6 month period I captured $1500.00 in silver apparently 99%pure...

Startling, to say the least.

How much - how many rolls of film - sheets of paper - were processed to reclaim that much silver?

I don't use anywhere near $1500 worth of film/ paper in a year.

 

[Kirk Keyes]

If the relationship between maximum density and silver content in the final image is not fixed for any given sensitive material, positive or negative, given the same processing, then we have no basis for charts of contrast vs time and temperature of development.

Well of course it is! Who ever made the claim otherwise?

But, when changing from one material or set of developer to the next, you should not expect it to be so.

 

[Ole]

So what you are telling me is that if I superpose two Wratten gelatin filters each of density 1.0, I will not have the equivalent of a Wratten filter of density 2.0. Sorry, I don't believe you. If the two are in contact so that there is no question of loss due to reflection between them, you will measure the density as 2.0. Three of them will get you 3.0. You know that as well as I. You can do the same with two pieces of film. The density of the sum will be the sum of the densities.

Tangential to the topic, but...

That is correct if and only if at least one of the filters is an ND filter. Adding two coloured filters give other results varying from 1+1=1 to 1+1=inf.

 

[dancqu]

Well, OK though there were a lot of .......... twixt the ANSI and the
table. I thought it might be from the ANSI but on second thought
could see no reason they'd list values. There high end, 1.5, is
mid-value of those of Henry. None of those he lists come
close to .8 . Dan

 

[Helen B]

'but on second thought
could see no reason they'd list values.'

... to give you an idea about the area of sample required to produce roughly the right amount of silver for whichever method you were going to use.

Best,
Helen

 

[gainer]

"Experiments by Sheppard and Ballard found that a particular film, when all silver was fully developed, could have an optical density of between 1.34 and 6.00. Same silver g/cm², widely different optical densities."
And I suggested that the developer had to be different in each case, or we would have no basis for time and temperature development charts. The finding of Sheppard and Ballard is in fact a basis for the need of different charts of Dmax, contrast index and so on as functions of time and temperature for different developers for the same film. Your quote did not specify whether the silver content was that before exposure and processing or the result of exposure and processing.

Why all this bickering over things that we don't need to knw to make fine photographs? Someone asked about silver content of emulsions. Now we know that there can be many different values depending on whether the value in question is before or after development. We still have not quantified the answer in any useful form.

 

[dancqu]

Absorbed twice I think more accurate. It's usuall to say,
"light travels through the silver". My understanding is that
the silver is black and opaque.

As for quantity of silver, film vs paper, the very slow document films and
the very slow papers may have near same silver. I've heard that paper
and the very slow films may have similar grain size. I've no data on
that or the silver amounts in microfilms. Dan

 

[Ed Sukach]

I'm still wondering about the amount of silver washed away - and into the effluent chemistry during processing. Anyone have any information?

 

[gainer]

All through this thread we have been discussing two things: silver content of various films and papers as they come off the line, and the silver content in exposed and developed images. Sometimes, the distinction has not been made.

Silver is not entirely opaque. We do have half-silvered mirrors which transmit as well as reflect. Very thin films of many metals behave similarly.

To answer Ed's question requires knowing the initial silver content and the image silver that remains. All the silver is removed from color film. It is probably worth the effort for commercial processors to recover the silver, as one of our contributors has testified. All but the image silver is removed from black and white film. I have heard that there is about a nickel's worth of silver in a roll of good film. Probably 1/4 of that is kept in negatives, although I have in my recent experiments wound up with much less than that.

 

[Kirk Keyes]

Absorbed twice I think more accurate. It's usuall to say,
"light travels through the silver". My understanding is that
the silver is black and opaque.

Dan, yes - absorbed twice is more accurate for what is lost. But then, some of that light does make it all the way back through!

As far as silver being black, the extremely small particles of the Cary Lea Silver I mentioned above are strongly yellow, that's why they use it as a filter in color films.

 

[Kirk Keyes]

All through this thread we have been discussing two things: silver content of various films and papers as they come off the line, and the silver content in exposed and developed images. Sometimes, the distinction has not been made.

Silver is not entirely opaque. We do have half-silvered mirrors which transmit as well as reflect. Very thin films of many metals behave similarly.

The analytical methods that Helen listed will work for either processed or unprocessed film, even half-processed film - it doesn't matter when you are digesting the stuff in acid! The information on Henry's work was for processed prints.

Silver is not entirely reflective or opaque - here's a graph at the bottom of the page for fully silvered mirrors:
http://www.edmundoptics.com/images/catalog/4497.gif

Kirk - www.keyesphoto.com

 

[gainer]

"The analytical methods that Helen listed will work for either processed or unprocessed film, even half-processed film - it doesn't matter when you are digesting the stuff in acid! The information on Henry's work was for processed prints"

Now maybe we are getting somewhere. Supposing you just want to know what to expect if you do the analysis, you should be able to get a reasonably good estimate from the manufacturer's quote of silver content of unprocessed film and the optical density equivalent of deposited silver. If you are going for all the silver, as you do in color processing where none is left after processing, you may as well use the manufacturer's number. Incidentally, the optical density of any one black and white film-developer combination is proportional to the mass of deposited silver. Hurter and Driffield hypothesized that and proved it by very precise analytical methods many years ago.

 

[rbarker]

Pardon me for butting into the discussion late, but it seems to me that so far the discussion has been dancing around at least a couple of different questions. The first is the precise interpretation of Dan's original question, how much silver. The extension(s) of that question, however, are why?, and does it matter?

Based on some "silver-rich" film and paper marketing, for example, there is the implication that more silver means better images - whatever "better" means. So, the ancillary question, I suppose, is has there been a direct correlation made between silver content and (some objective definition of) the quality of the resulting image? The resulting maximum optical density would certainly seem to be part of that answer, but not all of it. It would seem to me that the potential increments in density would be at least as important from an image "data capacity" perspective.

 

[dancqu]

Why all this bickering over things that we don't need to know
to make fine photographs? Someone asked about silver content of
emulsions. Now we know that there can be many different values
depending on whether the value in question is before or after
development. We still have not quantified the answer in any
useful form.

I asked about the silver content because I'm about to
continue with some film, paper, fixer experiments.

The silver's value in question is that of the unexposed
emulsion. That is worst case for a fixer. I doubt that
developing such an emulsion will have any effect on
the loading of the fixer.

Helen B has provided some very quantified information;
grams/meter sq., max. D, and density to quantity ratios.

Years ago when APUG was new to the WWW I posed a
question concerning the amount of good hypo going down
the drain.

This is an example; Ilford's single bath Rapid Fixer Archival
Fix routine. When they had Universal on the market, it at
1:3 was good for 40 8x10s/liter. Universal is no longer
the product and that routine has been droped.

With Rapid Fixer 1:4, 10 8x10s is the limit. With the same
fixer at 1:9 10 8x10s is the limit. Same limit, 'film' or 'paper'
strength. I dare say a print will fix at either strength
just as quickly and intend to test that.

I'm quite sure Ilford is backtracking. They do recommend
the two-bath method. Dan

 

[paul ron]

Back to basics....

I am following this conversation on 2 sites and neither has even touched on the actual amount of real silver in any emulsion yet. All I see is guess work based on densitometry calculations written in the 1800s used to calculate silver in fully developed negatives and prints of our recent past, 20 and 30 years ago, calculating grain size/mm², crazy reflectance index calculations, blah blah blah. Anyone have an actual chemical formula so we can stop this crazy guessing game? What the heck is in an emulsion?

If you know exactly what the formula or chemical composition of an emulsion is by volume, you will better be able to calculate at what point the fixer, another chemical compound of exacting measurements and proportions, will reach it's exhaustion point. It's that simple.

GIVEN: We know the thickness of the emulsion on a film, it's published by the film manufacturer. We know exactly what the area of a our film is LxW=area... xThickness=cubic volume. We then have a calculation of the actual amount of emulsion on that piece of film, now based on that volume calculate the actual amount of silver in that volume on that piece of film...

SO... if we had the chemical make up of an emulsion... calculating HOW MUCH silver is in the emulsion by volume and exactly how much volume of silver compound the fixer can chemically handle will answer all your questions to the molecule.

NOW... Does anyone have a formula for TMAX, Portriga, Polymax TRIx?... liquid light??? ANY data at all to make an actual emulsion?

 

[Kirk Keyes]

The first is the precise interpretation of Dan's original question, how much silver.

I think Helen gave some very definite answers to this. Even though they were ranges, you most certainly can't give a precise answer until you start naming specific products.

So, the ancillary question, I suppose, is has there been a direct correlation made between silver content and (some objective definition of) the quality of the resulting image?

For B&W prints, the reference I gave for Henry's work, and the actual values that Helen gave from said work should have somewhat answered this - for a criteria of maximum black, there is no correlation to silver content. I'm sure other criteria could be used...

Kirk - www.keyesphoto.com

 

[Kirk Keyes]

With Rapid Fixer 1:4, 10 8x10s is the limit. With the same
fixer at 1:9 10 8x10s is the limit. Same limit, 'film' or 'paper'
strength. I dare say a print will fix at either strength
just as quickly and intend to test that.

I suspect the longer fixing time of the 1:9 dilution has an effect on the final capacity of the solution. So you should think about how you are trading off the properties of fixing speed with economy, i.e. higher strength solution is faster, but lower strength solution is more economical. It's up to you to decide which you find more desireable or a greater benefit.

If you're really concerned with "wasting" fixer, use the 1:9 solution. And, if you really want to extend the economy of your fixer, do a double fix procedure.

 

[Kirk Keyes]

Anyone have an actual chemical formula so we can stop this crazy guessing game?

Where's the guessing in actually measuring the amount?

What the heck is in an emulsion?

See this link for instructions on making a simple photographic emulsion: http://www.rit.edu/~bekpph/Chemistry/6_AgX.html

If you know exactly what the formula or chemical composition of an emulsion is by volume, you will better be able to calculate at what point the fixer, another chemical compound of exacting measurements and proportions, will reach it's exhaustion point. It's that simple.

Well, now we are back to doing calculations on the back of a napkin at lunch with our slide rules... The only way to know exactly is to analytically measure it.

Kirk

 

[Kirk Keyes]

I dare say a print will fix at either strength
just as quickly and intend to test that.

I'm quite sure Ilford is backtracking. They do recommend
the two-bath method. Dan

Dan - It may be that Ilford is backtracking - perhaps they found that people were not sufficiently careful with the older method and they found that the newer recommendations allow for a better margin of error in processing times.

I look forward to seeing what you determine with your tests.

Kirk

 

[Bob Carnie]

Hi Ed
re: your doubt of my figure of $1500 for 6 month period

The 6 month period included all film processed, contacted , all fibre fix, all ciba bleach fix, all ra4 bleach fix.
We as well accept used fix from darkroom users that know we recover chemicals.
To be fair we process thousands of rolls , sheets of film a year, and I print daily with a fairly heavy show,portfolio clientelle.
But , to my point we are a very small shop compared to the Large Photo Labs and if we can save this type of silver every 6 months think of the amount of silver going down the drain if it is not being recovered.( how many home darkrooms are capturing their chemistrys?)
I would hope every one on this forum is recovering their used chemicals.

A recent poll on this forum indicated to me that there are a lot of talented indivuduals with heavy chemistry background, I totally defer to them on this issue. But until someone can prove to me and actually the Toronto Chemical Waste group that dumping photo chemistrys down the drain is ok for the enviornment , I will continue to reclaim my fix. As well get money for this practice.

 

[gainer]

Where's the guessing in actually measuring the amount?



See this link for instructions on making a simple photographic emulsion: http://www.rit.edu/~bekpph/Chemistry/6_AgX.html



Well, now we are back to doing calculations on the back of a napkin at lunch with our slide rules... The only way to know exactly is to analytically measure it.

Kirk

You and I may be the only ones here who know what a slide rule is, let alone how to use it. Don't knock it. A lot of very valuable research and development was done with sliderules. The Mercury project was not much beyond that stage. The best computer we had could not be guaranteed to run more than 80 hours between failures. I had to invert 10X10 matrices using a Marchant electromechanical desk computer.

We have been talking back and forth comparing apples and oranges. There are certain facts that are as true now as they were in the days of Hurter & Driffield. They were not amateurs at analytical chemistry. The method they used to assay the amount of silver in a plate of known optical density was not much different from that described by Helen. They ascertained by ingenious experiments that human visual response is logarithmic, as we know by the fact that the just noticeable difference between two brightnesses is a constant ratio over most of the range of perceptible brightnesses. They proved that in any given colloidal silver suspension, the optical density is proportional to the mass of silver per unit area. This finding allowed the use of the familiar characteristic curve to analyze developer performance by maesurement of optical density, which is very much easier than the quantitative analysis of silver content. They also knew that maximum density was not correlated to silver content of the undeveloped emulsion alone.

We in our brilliance redicover many things. I don't know how many of you have access to the Hurter and Driffield Memorial Volume, but if you can find one it will be very interesting reading. Mine was given to me by a friend.

 

[Ed Sukach]

Hi Ed
re: your doubt of my figure of $1500 for 6 month period

The 6 month period included all film processed, contacted , all fibre fix, all ciba bleach fix, all ra4 bleach fix.
We as well accept used fix from darkroom users that know we recover chemicals.

I was careful to avoid any indication that I doubted your $1500 figure... and I do not. I was trying to get some indication of how much silver I could expect to recover, processing X rolls of film and Y rolls of paper. I have an idea that it would NOT be economically viable, or for that matter, not worth the effort, for ME to attempt recovering silver from my used chemistry, based on the experience of others.
You state "$1500", but that is meaningless without some correlation to the amount of film, or chemistry involved.
You cite an intense Portrait Studio activity... and the reclamation from others who bring their used chemistry for disposal. All well and good, but there is no indication of a finite amount of effluent chemistry.

I have heard - and hearsay is rather nebulous information to go on - that, "A nickel's worth of siver is flushed out of a roll of film in processing." That is US$ 0.05 per roll, and at the rate of 100 rolls a year, that indicates a grand total of $5.00. How much does a small Silver Recovery System cost, and what value can we project for the labor involved, and the expenses incidental to the process as a whole - to the point where our proceeds can be deposited in our bank account?

You also - I don't want to use the term "demand"... let's say "challenge" us 100-rolls-a-year lab operators to PROVE that our dumping of silver (and I would assume other chemical compounds) do not "harm the environment." If you remember, I was also seeking information about toxicity - without that I can't reasonably form an opinion either way - nor will I argue the question.

In the United States - at least in this State, the definitive answers of chemical disposal are left to our local Fire Departments. I've already contacted mine, about operating a low volume darkroom. Their first question: Commercial or something else?" I discussed, at length my activity levels and finally received their answer... essentiaily, "Too low a level for anyone to be concerned about".

So .. my question still stands unanswered: "How much Silver per roll, or per print - and what toxicity levels - are we talking about?" Without that information I cannot define the problem.

 

[dancqu]

"How much Silver per roll, or per print
and what toxicity levels are we talking about?"

How much? That question was answered twice by Helen
B's posts this thread.

My understanding is that fix down the drain is oxidized. The
thiosulfate which might be thought of as sulfur sulfite becomes
free sulfer and sulfate.The silver converts to the extremly
insoluable and non-toxic sulfide and stays so. Dan

 

[dancqu]

I suspect the longer fixing time of the 1:9
dilution has an effect on the final capacity of the solution.

The point is, diluted 1:4 or 1:9 the capacity per liter is the same.
Do a little arithmatic. From Helen B's post take 1.6 grams/meter
square silver. Assume half ends up in the fix. Ilfords maximum
for archival results is .5 gram per liter. An 8x10 is 1/20 of
a square meter. How many 8x10s can be fixed? Dan