Age-fogged B&W materials: the definitive guide to working and succeeding with them

[David Lyga]

Well, as I said, it would have to be tested. You posit a hypothesis, we could now try to figure out whether it is indeed as deterministic as it seems at first glance, and if so, how it might work. Or we could take it at face value. For me, personally, it's kind of a moot point since I don't have much expired film or paper to work with and my interests are in other areas. From a hypothetical viewpoint, it's amusing to think about, that's all. It's not about homage etc. at all for me, just curiosity.



So did you do the A/B testing of a regular developer with a very short development time (or a regular developer diluted way down) vs. your special-purpose developer? What kind of sensitometric or visual differences did that yield? Just to keep this clear - I don't doubt your approach works. I'm curious as to how it works, i.e. what the underlying mechanism would be. Perhaps someone with more knowledge about the theoretical aspects of developers could chime in; maybe @Lachlan Young?

No no formal "sensitometric", just eyeball, steadfast eyeball ballistics targeting a higher amount of visual quality. - David Lyga

 

[David Lyga]

Development progresses from the grains that received the most exposure down to those who received less (and ultimately none at all). Based on this, I find it hard at this point to determine whether your 'suppressed threshold' really is any different from just very weak development. As I said before, it would be interesting to test this by taking a regular developer and develop very briefly, and compare the results to your developer. Mind you, in both instances very liberal exposure would be necessary.

Of course 'weak development' suppresses threshold density. That fact is inherent it its very definition. However, my developer suppresses much more for a longer time, while image progresses in the interim. That simple: I am not so versed in the intricacies of science. - David Lyga

 

[koraks]

Nobody is talking about banning anyone. Settle down, take it easy and relax.

I think your hypothesis is interesting and all I'm saying is that it would be even more interesting if someone could validate it. My question was simple: did or did you not do the A/B tests I proposed? I understand you haven't done sensitometry or densitometry - that's fine. Did you do visual comparisons of a regular developer (short and/or dilute) vs. your threshold-metol concept? And if so, was it possible to replicate the results across a few different types of material (film or paper)?

 

[David Lyga]

To answer your question: This specific time, no.

However, that particular attempt seemed completely unnecessary because with this film, trying as such as you just recommended, previously .... that is how I had decided to search for another alternative: normal developers in all aspects had failed me. Previously, this film, and with films like it, I had tried with regular developer, then, again, adding BZ and then, again, doing all sorts of other things. I could not get a decent image anyway that I had tried to get one. Koracs, YOUR query about developing in normal developers (and failing in all aspects) is what forced me IN THE FIRST PLACE to delve into the matter. I look forward to hearing about others' validations. If not, I still do not feel that I have failed because what I now see amazes me in my darkroom. I can speak for myself, only, but would be very surprised, indeed, if validation were not forthcoming, especially for paper. - David Lyga

 

[MattKing]

Just a reminder to the community in general, and in this instance, @David Lyga particularly, that the Moderation team consists of Sean - Photrio's owner and administrator - and a group of volunteers who are also interested members who participate regularly in the subjects of the threads themselves.
A very clear majority of my posts since I became a Moderator are not related to my Moderation role - they are just attempts to contribute to the threads. I believe the same applies to the rest of the Moderation team.
Even when I am posting as a Moderator, a large percentage of those posts are aimed only at helping the site run smoothly, in a well organized manner.
Unless my posts say very clearly something about posting as a Moderator, member bans or rule breaches or something of that sort, they aren't in any way related to such actions!
You can feel free to engage in spirited discussions with any of us Moderators - including @Sean , about anything substantive. The only thing you need to avoid is disagreements about moderation actions - those should be taken up with us directly, outside otherwise substantive threads.
In short - we Moderators welcome other points of view on things photographic. We all joined this site because of our photographic interests, and are quite happy if, as a result of the discussions here, we learn new things about photography, even if it turns out we were wrong in what we understood before. And we would NEVER take any moderation actions because someone doesn't agree with us, as long as their disagreement is communicated in the reasonable and civil manner that the rules of Photrio require for all posts.

 

[David Lyga]

Queries, doubts, even a vestige of disbelief are normal attributes, pre-requisites to something as profound as this photographic finding. I not only allow this emphasis, but encourage it. Like in a courtroom, the bottom line is facts, not fantasy, not foolhardiness, not anything else or anything in between. I support, fully, skepticism and demand for proofs. I hold nothing against such honest inquiries and, to be quite frank, would be insulted if they were not forthcoming, because that, to me, would show a veneer of knee-jerk support for me based upon little that is substantive. I do not want that.

I will say this to all: If the majority verdict does not exonerate me and my findings, I will be genuinely surprised. To ME, it will be a little like everyone here stating that I am five feet tall when I know that I am six feet tall. Who to believe? Either the vast majority or my very own mind and affirmed physical measurements? That duplicity would prove to me something which I would find to be unable to reconcile and believe. That said, I do honestly believe that everything I have brought forth in this thread, verbal and visual, are the embodiment of everything I deem to be honest and straightforward.

I have said a lot with this thread and have made serious assumptions. I encourage full skepticism and accountability and take nothing brought forward as being base or vile. But, again, I am in a dilemma: If everyone ends up disagreeing (ie, telling me that I am but five feet tall) do I fall into agreement with them or do I hold onto my own mental assuredness? This is a question which can be applied to many other aspects of life. - David Lyga

 

[Don_ih]

it would be even more interesting if someone could validate it.

I can try some things out, using very similarly degraded materials. I have TriX that has extreme base fog and I have thousands of sheets of paper that develop to show pavement at dusk. I have all the required chemicals. But I have no time at the moment - it may take a while.

 

[David Lyga]

I can try some things out, using very similarly degraded materials. I have TriX that has extreme base fog and I have thousands of sheets of paper that develop to show pavement at dusk. I have all the required chemicals. But I have no time at the moment - it may take a while.

How I do wish that I could have one sheet of that paper. - David Lyga

 

[Don_ih]

If everyone ends up disagreeing (ie, telling me that I am but five feet tall) do I fall into agreement with them or do I hold onto my own mental assuredness?

Unlike your height, people can report whether or not they can get your method to work. Some people will likely get it to work, some will likely not. People who don't try don't get a vote - much like people who have never measured your height don't get to say how tall you are.

There is possibly a theoretical vantage point from which your method could be assessed. But I'm a bit doubtful, since there is not much value (particularly commercial value) to working out a way to rescue drastically outdated materials.

How I do wish that I could have one sheet of that paper.

I have paper of all grades of fog - from slight overcast to midnight.

What about developer-incorporated papers, like Ilford MGIII (aka, useless)?

 

[David Lyga]

For those of you wishing metric conversion factors, I offer these:

1 mL metol = 0.6 gram
1 mL hydroquinone = 0.67 gram
1 mL sodium sulfite, anhyr = 1.59 grams
1 mL potassium ferricyanide = 0.93 gram
1mL sodium carbonate, mono (washing soda) =1 gram

- David Lyga

 

[David Lyga]

Unlike your height, people can report whether or not they can get your method to work. Some people will likely get it to work, some will likely not. People who don't try don't get a vote - much like people who have never measured your height don't get to say how tall you are.

There is possibly a theoretical vantage point from which your method could be assessed. But I'm a bit doubtful, since there is not much value (particularly commercial value) to working out a way to rescue drastically outdated materials.



I have paper of all grades of fog - from slight overcast to midnight.

What about developer-incorporated papers, like Ilford MGIII (aka, useless)?

It would be so nice if everyone lived in Philadelphia. (EDIT: Nice in only CERTAIN aspects.) - David Lyga

Ilford MultiGrade was the horrible paper in my test. So, it works fine. - David Lyga

 

[Rudeofus]

That seems to match very well with what I said:

The red line would be representative to what I propose.
Of course, the plot above does not contain a curve that represents David's approach.

You would want the right shifted toe region of this red plot, but you wouldn't want the resulting low contrast. Remember, what Michael compared this H&D graph to, it was all a bunch of extra low contrast devs. Thing is, that aged material already lacks contrast, so your developer has to build up contrast like mad. How would you build up contrast with XTol? Extend dev time, which you must not do, because then the toe would move left.

I believe, that David has searched for and found a speed losing extra high contrast developer. Compare his recipe with Agfa/Ansco-22 or Kodak D-16.

 

[chuckroast]

I am not going to live forever so I might as well allow others to benefit from my hard-won findings on the matter of ugly age-fogged B&W materials. I have written previously about this but this latest formula seems to be my best yet, by a substantial margin. I have a 'different' way of formulating such and, certainly, am not a chemist. But this does work: with film and, especially, with paper. Read, heed, and proceed to try this. It is cheap. I do not have photos for proof YET; hopefully, they will be posted within a week.

First, a bit about the theory part: It seems to me after years of experimentation that there is a 'trigger point' for hydroquinone that must be met, and ONLY met, with no extra help. What I am getting at here is this: Metol is the developer that strives to bring out threshold density, WHETHER THAT DENSITY MANIFESTS AS EITHER FOG OR EMERGING IMAGE DETAIL (the developer does not know the difference between the two!). And, as we know, hydroquinone is the developer which strives, at all costs, to augment contrast. Hydroquinone, alone, is bad as a developer: so slow, so painfully slow, as to seem worthless. However, a tiny bit of metol can act as a trigger to cause the hydroquinone, finally, to come to life IN A WAY WHICH DOES NOT APE THE SYNERGIZED EFFECT OF THE M/H COMBINATION. Since the amount of metol is so small, so small, so really small, the threshold density keeps getting suppressed despite the hydroquinone being allowed to come to life. That is about as clear a presentation as I can present to you.

Here is my formula that I now use for almost every B&W film and for all papers. Yes, it is that good, and cheap and simple to make. However, I am used to measuring things a bit differently than most, so you will have to accept that. I measure most dry chemicals by volume, so you will have to get an ACCURATE calibrated cylinder to measure small volumetric quantities. Not so difficult, right?

First you must make two solutions that you can draw from every time you mix my developer. Metol solution (keep airtight) (MS) is made this way;

2 mL of sodium sulfite, anhydr
1 mL metol
WTM 100 mL.

Of course, again, keep the MS airtight, like with any developer.

(Naturally, if you want to make a whole liter, multiply the quantities by ten, but the smaller volume is sufficient; I use thrown out tiny liquor bottles, easily found in filthy Philadelphia, and add tiny glass marbles to keep the volume to the rim.)

The second solution is restrainer solution (RS):

1 GRAM of benzotriazole
WTM 100 mL

The RS does NOT require being kept air-tight. The REASON why I WEIGH the BZ is because, in its history, it has come in different forms: feathers, large granules, powder. Thus, to assure accurate measurement, I simply take its mass, metrically.

Now that you have the critical two solutions, I present the FORMAL formula for all:

To make a small 100 mL quantity of STOCK solution:

3 mL sodium sulfite, anhydr
5 mL of MS
2 mL hydroquinone
6 mL sodium carbonate, mono (this is Arm& Hammer washing soda, sold in its most stable, packaged form: monohydrated; store brand is the same, if cheaper)
2 mL RS
WTM 100 mL

When you accurately measure in the calibrated cylinder, tap down slightly to get the powder flat; do not tap down hard, as if your life depended upon it.

How to use the formula: for use with either film or paper, mix from 1 part formula + 4 to 9 parts water, depending upon the material. I find that slower films, like Panatomic-X or Plus-X can use the more dilute
1+9 and that faster films, or TMY 100, need to be diluted less. Kodak TMX 3200 needs the FULL 1 + 4. But, first, a note on trying this out: do not be foolish and wasteful and just plain stupid by thinking that whole rolls or whole sheets are needed ‘to test’. If I had done this in the past years, I would be bankrupt by now. A 36 exposure roll of film lasts, for me, for 36 tests! Learn to cut off about one frame (keep the roll truly light-tight) and learn how to place that frame onto the film aperture gate (of a manual SLR) in the dark (use tape if you are afraid of the curtain eating it up). Then carefully close the back without moving the film. With paper, cut a piece about 1 or 2 inches square (3 or 4 cm) and target that on the easel to an important part of the picture, covering part of the paper with a coin in order to compare both fog and image quality. For developing this single frame, I use the old style film can: one frame fits perfectly, and add 10 mL of WORKING solution, cap it, then roll it in a water bath for the duration of development time. It is very important to know whether the film can is truly impervious to light. Otherwise, work in dark with a timer. The newer ones, even if black, are NOT light tight. Those made 30 to 40 years ago usually are. Do not assume, or you will spoil everything. Also IMPORTANT: for ALL B&W work I use 80 Fahr (26.7 C) solely because that is what is most comfortable to me and easiest to maintain. If you use colder, increase the development times a bit to compensate. For the tiny pieces of paper for testing, use tiny trays. (Dollar Store?) Make your costs for tests miniscule. I have always been frugal and never regretted it. In fact when Warren Buffet’s wife recently complained about the price of a cup of coffee, I did not laugh like so many jerks did, given her money; instead, I applauded her.

You are going to have to do many tests in order to get this right. But, my helpful indications follow:

First, how fogged is the material? If slightly fogged or even moderately fogged, you might be able to get away with normal development with dilute Farmer’s after fixation. Here is how I mix MY Farmer’s:

To make the BLEACH (B): 1 mL potassium ferricyanide in WTM 25 mL. To make the Farmer’s reducer(lasts about half an hour but depends upon strength), mix one part B to one part of (unused) paper strength fixer plus anywhere from two parts water to eighteen parts water. The stronger the fog, the less dilute the reducer needs to be. Mixed, it will not last too long but usually half an hour is OK. I use percentages, because they are easier for me to understand: The first is 1+1+2 = 50% and the second is 1+1+18 = 10%.

To remove this small amount of fog, simply place the film or paper (after fixation) into your choice of diluted Farmer’s. That said, now let’s assume that you need my formula for combatting serious age-fog.

First, film: Let’s take a worse-case scenario here: Kodak TMZ 3200 film that has been sitting around for twenty years or so. WOW what FOG!!! Barely an image visible with normal development. Now, do this: shoot a frame at, say, not at its box speed of EI 800 but, instead, at EI 12, a full six steps more exposure. Then use my formula (1+4) for eight minutes (remember I am 80 Fahr) and see what you get. If you get a reasonable image, slightly overexposed, with little to moderate fog with great contrast, you have succeeded. Simply use the Farmer’s (maybe 20%) to make that negative clear and pristine. Examine the image detail and shadow detail and make your next experiment to remove the noticed faults. Maybe give less, more exposure and/or more/less development.

Sorry, this is what you have to do in order to target the supreme success, but it is worth it. I have Multi-contrast Ilford paper which is so age-fogged that it is YELLOWED on the reverse, like old newspaper!!! It is unbelievable what I get done with this developer and I will show you when I get a chance to take and upload photos in about one week. For paper, I usually use 1 part formula + 4 parts water and develop for from 2 to 4 minutes. You have to examine the fog level under that coin that you placed upon the paper and, if the fog is rather low (less than 50%) you might be able save the print with Farmer’s.

In summation, this is a race between gaining adequate contrast (difficult with age-fogged materials) and subduing age-fog. The more development the more contrast but, also, the more fog. If you are not prepared to suffer, expend time (not money) and accurately note your findings for welcome repetition, you are not prepared to read this posting again for a better understanding. - David Lyga

MODERATOR'S NOTE: The following clarification, which has been added later in this thread by David, should be helpful for those who are familiar with David's earlier work on this subject:.

"NOTA BENE TO ALL: Although my previous posts related to age-fog in B&W materials were well-thought out at the time, I do consider those writings, now, to be subordinate to those within this current post. Much experimenting has been done in the interim and, although the previous writings (concerning this specific matter) do contain still-relevant ideas, exact particulars have been modified. Honestly, I cannot foresee saying anything negative about this current post in the future, so happy am I with the results. My advice is to take my previous writings on the specific topic to be something to compare this thread with, but please allow this thread to predominate. With this (necessarily) said, I have no objection with the mods thus "illuminating" the past. Thank you. - David Lyga"

This is most interesting to me.

I have had gotten good results from very old film with developers that have no hydroquinone in them at all.

The images below are scans of prints made from Super XX film that expired in 1961. The box was sealed and I opened it in 2021 to try this. The imperfections in the images you see are due to the physical deterioration (chipping/sticking) of the negative emulsion, not from the development process.

The negatives were exposed at the box speed of 200, and semistand developed for 60min (2 min initial agitation, one 15 sec agitation at 31 min).

This first image was developed in D-23 1:1

The second was developed in Pyrocat-HD 1.5:1:200

The grain is particularly visible with D-23 since SuperXX was pretty grainy film.

Admittedly, Pyrocat-HD doesn't have hydroquinone but it has phenidone in it.

 

[Rudeofus]

@chuckroast How's the fog in these samples? Any chance you can show us, what the negs look like?

 

[chuckroast]

@chuckroast How's the fog in these samples? Any chance you can show us, what the negs look like

Lemme see if I can find em. Will check back if I do.

 

[David Lyga]

This is most interesting to me.

I have had gotten good results from very old film with developers that have no hydroquinone in them at all.

The images below are scans of prints made from Super XX film that expired in 1961. The box was sealed and I opened it in 2021 to try this. The imperfections in the images you see are due to the physical deterioration (chipping/sticking) of the negative emulsion, not from the development process.

The negatives were exposed at the box speed of 200, and semistand developed for 60min (2 min initial agitation, one 15 sec agitation at 31 min).

This first image was developed in D-23 1:1

View attachment 397114

The second was developed in Pyrocat-HD 1.5:1:200

View attachment 397115

The grain is particularly visible with D-23 since SuperXX was pretty grainy film.

Admittedly, Pyrocat-HD doesn't have hydroquinone but it has phenidone in it.

Phenixone

This is most interesting to me.

I have had gotten good results from very old film with developers that have no hydroquinone in them at all.

The images below are scans of prints made from Super XX film that expired in 1961. The box was sealed and I opened it in 2021 to try this. The imperfections in the images you see are due to the physical deterioration (chipping/sticking) of the negative emulsion, not from the development process.

The negatives were exposed at the box speed of 200, and semistand developed for 60min (2 min initial agitation, one 15 sec agitation at 31 min).

This first image was developed in D-23 1:1

View attachment 397114

The second was developed in Pyrocat-HD 1.5:1:200

View attachment 397115

The grain is particularly visible with D-23 since SuperXX was pretty grainy film.

Admittedly, Pyrocat-HD doesn't have hydroquinone but it has phenidone in it.

There ARE old films which do show relatively low fog. Just a few years ago I had a bulk roll of TX factory-stamped 1958 and was astounded by the low fog level. D-23 delivering your low fog is rather interesting. But, for all intents and purposes, phenidone "IS" hydroquinone as far as contrast goes. - David Lyga

 

[Don_ih]

Just a few years ago I had a bulk roll of TX factory-stamped 1958 and was astounded by the low fog level.

I have a similarly old roll of TriX - expired mid 50s - and it also can easily be developed with no fog.
Kodak used to make magical stuff.

 

[koraks]

You would want the right shifted toe region of this red plot, but you wouldn't want the resulting low contrast. Remember, what Michael compared this H&D graph to, it was all a bunch of extra low contrast devs. Thing is, that aged material already lacks contrast, so your developer has to build up contrast like mad. How would you build up contrast with XTol? Extend dev time, which you must not do, because then the toe would move left.

Well, if you look at the plot I quoted from that other post, what I find remarkable is that the contrast of the red line really isn't that low at all. It's surprisingly normal. Keep also in mind that David proposes very liberal exposure. This was not included as a factor AFAIK in the other experiment, which really was about something else. I also don't see how contrast on an old material is inherently low. b+f is high, so image-wise contrast may seem low until you lift the image curve sufficiently over the dense b+f. It's a bit like a volcano or an iceberg in the ocean; it may seem like a small bump on the ocean surface, but that's only because most of it is underwater. If you lift it up, it turns out to be pretty darn big anyway.

I believe, that David has searched for and found a speed losing extra high contrast developer. Compare his recipe with Agfa/Ansco-22 or Kodak D-16.

That's very interesting; if you calculate the molar ratios of m:q in those developers, you end up in the 1-3% region or thereabouts (1-3%mole metol per mole of HQ). The optimum of superadditivity is supposed to be around the 10% mark, so these developers sit very far below that mark. What's interesting is that David's developer seems to be around the 2-3% mark as well. Do we also know why or how this combination would suppress fog while favoring image-wise contrast? We (sort of) know how it works with benzotriazole - which is used in David's soup as well. Can we determine that the MQ ratio adds much to the party except just to slow things down?

 

[Rudeofus]

Well, if you look at the plot I quoted from that other post, what I find remarkable is that the contrast of the red line really isn't that low at all. It's surprisingly normal. Keep also in mind that David proposes very liberal exposure. This was not included as a factor AFAIK in the other experiment, which really was about something else. I also don't see how contrast on an old material is inherently low.

I wouldn't claim expertise with old materials, but the ones I had my hands on yielded unpleasantly low contrast. This was both with B&W paper and an old stash of RA-4 paper. Liberal exposure shifts the H&D curve left, but it doesn't tilt it. The "red line" looks like gamma=0.5 or lower, which is well below 0.7 "normal". This may also be the reason, why David goes the "develop plus Farmer's" route with paper: paper has its contrast mostly baked in, and the only way to raise contrast may well be a non-linear acting bleach.

Do we also know why or how this combination would suppress fog while favoring image-wise contrast? We (sort of) know how it works with benzotriazole - which is used in David's soup as well. Can we determine that the MQ ratio adds much to the party except just to slow things down?

The main property of this mix appears to be "lose speed while raising contrast", which is a good thing in this specific case of aged materials. You want to underdevelop the toe region while giving strongly exposed regions a boost.

Remember, where this "10% is the optimum" ratio came from: this was not "optimal sharpness" or "finest grain", it was a "fastest development with the least chemistry" type optimum. If we reduce Metol, we forego some of that "fastest development" in all regions - to our advantage.

 

[koraks]

The "red line" looks like gamma=0.5 or lower, which is well below 0.7 "normal".

Yes, but given the dramatically reduced development time, I find it remarkably close to normal, still. And 0.5 is perfectly printable and scannable.

The main property of this mix appears to be "lose speed while raising contrast", which is a good thing in this specific case of aged materials. You want to underdevelop the toe region while giving strongly exposed regions a boost.

Remember, where this "10% is the optimum" ratio came from: this was not "optimal sharpness" or "finest grain", it was a "fastest development with the least chemistry" type optimum. If we reduce Metol, we forego some of that "fastest development" in all regions - to our advantage.

Yes, exactly; what I'd like to figure out and/or get a handle on is what kind of chemical mechanism is involved here in achieving that effect.

 

[David Lyga]

The most crucial part of my formula is the 1:40 relationship of M:H. Considering the small 100 mL of my stock formula, 5 MS = 0.05 mL of metol. (0.05 divided into 2 HQ = 40).

The amount of RS was determined as having to be adequate to attack fog while not forcing unduly long development times. The carbonate's sole purpose was to speed up development since the HQ had so little help from the miniscule amount of metol. The carbonate does NOT affect fog, only development time. - David Lyga

 

[koraks]

I see, thanks for adding that. I assume you did a series of tests to determine the optimum M:Q relationship, right? What effects did you note if the ratio strayed too far to the left resp. right of the ideal ratio you determined?

The amount of RS was determined as having to be adequate to attack fog while not forcing unduly long development times.

Yes, that makes good sense, too. I wonder how much of the fog-suppression effect in your developer is due to the benzotriazole (RS) and what part stems from the combined effect of exposure, degree of overall development and the M:Q ratio (let's say the quantitative development vs. the qualitative development).

 

[David Lyga]

I see, thanks for adding that. I assume you did a series of tests to determine the optimum M:Q relationship, right? What effects did you note if the ratio strayed too far to the left resp. right of the ideal ratio you determined?



Yes, that makes good sense, too. I wonder how much of the fog-suppression effect in your developer is due to the benzotriazole (RS) and what part stems from the combined effect of exposure, degree of overall development and the M:Q ratio (let's say the quantitative development vs. the qualitative development).

To say that I did "a series of tests to determine the optimum M-Q relationship" has to beat even the Brits for gross understatement! In essence, this search was the very embodiment of my quest for the Holy Grail.

That (finally) determined, I then set out to find just how little RS I could get away with using in order to keep development times manageable. And, also (being frugal) to find how much I could dilute the stock solution! The contributing factor to make all of this happen to my liking was giving PLENTY of exposure, since I had both low metol and BZ working against quick development. - David Lyga

 

[David Lyga]

To continue with your question: if I had too much metol the fog would not be adequately suppressed. If I used too little metol development times would be far too long. I try to make things comfortable and repeatable.

 

[David Lyga]

I see, thanks for adding that. I assume you did a series of tests to determine the optimum M:Q relationship, right? What effects did you note if the ratio strayed too far to the left resp. right of the ideal ratio you determined?



Yes, that makes good sense, too. I wonder how much of the fog-suppression effect in your developer is due to the benzotriazole (RS) and what part stems from the combined effect of exposure, degree of overall development and the M:Q ratio (let's say the quantitative development vs. the qualitative development).

Yes, you are correct. There are multiple factors contributing to suppression of fog: BZ, exposure (to provide distance between image and fog and also to enhance contrast), development time (to enhance contrast), choice of developing agent: (HQ but it needs a little help from metol). In fact, another way to gain contrast (especially with paper) is to overdevelop with some increasing fog and then restore with my Farmer's.

Jockeying all of these were formidable factors which took much effort and even more tedious time. - David Lyga