Perceptol & The Microdol Substitute Formula.

[Photo Engineer]

I didn't realise Henn worked on Perceptol

Having read all of Henn's Patent's we could probably easily find an additive which would have worked well with the films of that era.

A huge advantage today is that modern emulsions have changed and evolved and are now far less prone to Dichroic fogging, which is why many older formulae have come back into use.

I tested DK-20 supposedly the worst for Dichroic fog back in the late 70's and never had it with Ilford films, I was testing Monobaths to and some had it so was well aware of the issues.

Ian

I never said Henn did except to perhaps test them and compare Perceptol and others to his own formulas.

However, in view of the following posts on dichroic fog, it appears that some films are still sensitive to it.

Kodak was working on this problem when all B&W work was terminated.

PE

 

[Keith Tapscott.]

I never said Henn did except to perhaps test them and compare Perceptol and others to his own formulas.

However, in view of the following posts on dichroic fog, it appears that some films are still sensitive to it.

Kodak was working on this problem when all B&W work was terminated.

PE

AFAIK, Perceptol was introduced in the early 1970`s as an equivalent of Microdol-X. Perceptol superceded ID-48 which was probably a DK-20 clone. Agfa`s extra fine-grain developer was called Atomal FF which was a completely different developer than their standard Atomal.

 

[Photo Engineer]

Perhaps it is better to design a developer for a specific film type rather than make a "one-size fits all films" type of developer.
Isn`t that what Geoffrey Crawley tried to do with his FX series?

If it could be done, it would be done, but different developers do different things.

Crawley's FX series is currently being discussed here on APUG with respect to problems with modern films with high iodide. We have already agreed that they seem to fail to some extent with inadequate edge effects with these new films.

And, AAMOF, I do know that Perceptol is a rough equivalent to Microdol-X and this was near the end of Henn's work at EK just before he retired and Bill Lee took over that helm.

Kodak does publish a chart of film vs developer and include "NR" in places on the chart where a given combination is Not Recommended. At least they did that at one time.

This discussion also highlights the fact that Kodak had many of these technologies before others and did the basic R&D at great cost. Others introduced work-alike developers at lower cost and Kodak was often stuck with a higher priced product. (apropos of nothing but the fact that APUG members seek bargains over and over and hurt the originator of the new technology)

PE

 

[Nicholas Lindan]

I got it from a bloke - "I suppose the Sodium Tripolyphosphate could be left out if SOFT or DISTILLED water is used."

The word that gives the goose bumps is "suppose" - second only to "assume" in warning of problems to come. I was told by my first engineering boss that "assume" stood for "Make an ass of you and me".

Without a sequestering agent Microdol/Perceptol will produce dichroic fog on modern films. When Kodak added the "-X" to the name the added the sequesterant.

Kodak's MSDS doesn't list the sequesterant for Microdol-X, though they do disclose the mercaptan aminopolycarboxylic acid in the MSDSs for other developers and it is known (famous last words) that they add it to prevent dichroic fog, and it does have an 'X' in it's name - proof positive (cough).

It could be that Ilford is also keeping mum about the sequesterant and the tripolyphosphate is their for water softening properties, or is added because it improves the manufacturing process - a chemical of many uses, it seems. But it is also possible that it is added to prevent fog. I guess experimentation is in order - but I'll pass, I buy M-X - even at $10 for a gallon's worth of powder it works out to 16 cents a roll of 35mm film when used 1:3.

 

[Nicholas Lindan]

Perhaps it is better to design a developer for a specific film

Wouldn't that be nice. The only example I know of is Tech Pan and Technidol - and it was stunner.

Some developers do work exquisitely with some films: D76 1:1 and Plus-X; Microdol-X 1:3 and TMax-100. But I don't know of any other magic combinations - at least for the negatives that I like.

 

[Photo Engineer]

AFAIK, no sequestrant is connected to formation or prevention of dichroic fog. Silver ions do not form substantial protected complexes with this common class of compounds (sequestrants) in a way that would protect them from being reduced, if so inclined by the particular developer.

The sequestrants that we see as a class, inculding polyphsphates, hexametaphosphates, EDTA, NTA and etc are more active against divalent and trivalent metals such as Calcium and Magnesium found in hard water or Iron found in some water supplies. Even in these preferred cases, say EDTA-Iron+++, this easily is reduced to EDTA-Iron++ which in the case of Silver would be the equivalent of EDTA-Silver+ going to EDTA and Silver metal which is dichroic fog in simple terms.

The main use of the sequestrant is preventing precipitates with the components of hard tap water, if used, and will prevent sludging of Silver Chlorides that may form during development. Reduction of Silver Chlorides may continue unabated though to form dichroic fog if the film is so inclined.

No, I would have to say that the measures used to prevent dichroic fog are not due to a sequestrant.

PE

 

[Christiaan Phleger]

What does "mercaptan aminopolycarboxylic acid" do in the Microdol-X formula, would that be for the Metol or the Sulfite? Great fun following the thread.

 

[Photo Engineer]

I am not sure of the purpose of that compound, but due to the sulfur group on it (mercaptan), it has a good chance of grabbing hold of any Silver ions on their way to becoming dichroic fog. I've been thinking of that myself actually, as it was not a common chemical in use in other developers.

In fact, later developers used quite different chemistry and I was following those.

PE

 

[lensmagic]

Dichroic fog--what does it look like under magnification on the negative? I assume it is different from general fog.

 

[Photo Engineer]

Try this: Dead Link Removed

It has an excellent description and also a good argument for using an acidic stop bath.

PE

 

[Keith Tapscott.]

Try this: Dead Link Removed

It has an excellent description and also a good argument for using an acidic stop bath.

PE

Yes indeed. I have never seen the point in not using a stop-bath.

 

[Ian Grant]

As Ron says most people will see Dichroic fog with prints that aren't processed properly, poor stop-bath and exhausted fixer, where you get an inter-action of developer still not neutralised and fixer. An exaggeration of the conditions in a dev like DK-20.

Ian

 

[Keith Tapscott.]

What does "mercaptan aminopolycarboxylic acid" do in the Microdol-X formula, would that be for the Metol or the Sulfite? Great fun following the thread.

It`s another sequestering agent and is used in most Kodak B&W developers now. Ilford use it in their liquid developers, but use STPP in their powder developers.
The short name is Pentasodium Dead Link Removed

 

[Photo Engineer]

Interestingly enough, patents disclose use of mercaptan aminopolycarboxylic acid (often seen as - mercapto aminopolycarboxylic acid) as a good sequestrant for iron and gold. If this is so, then is offers two functions in this case. It is both a sequestrant for metals in tap water, and a sequestrant for silver ion that might be strong enough to prevent any dichroic fog.

PE

 

[phritz phantom]

what's the properties of sodium chloride in a film developer? i've seen chlorides used in emulsions for photo paper, but never in developers.
what does it do image-wise? since the formula has a preservative, it should have an accelerating function.
wouldn't the iodide from talbe salt work as an inhibitor (like in the fx-1 formula)? maybe using normal table salt would result in even better pictures?

 

[Photo Engineer]

Well, we have discussed the fact that with modern, high iodide films, the iodide developers have less effect than on older films, so lets throw that idea out. The Crawley formulas may have to be redesigned for modern films.

As for Sodium Chloride, NaCl, it is used as a mild Silver halide solvent in the developer to promote physical development by dissolving some Silver from the film. At the same time, it promotes Dichroic Fog which has been the topic here lately.

PE

 

[Ian Grant]

Sodium or sometimes Ammonium Chloride is a restrainer and silver solvent, it helps to give the extra fine grain in Microdol-X and Perceptol. It was used in other developers during the 1930 to give fine grain.

It's very rare to add iodide to a developer except as a very small trace in some high acutance developers which is why Iodised table salt shouldn't be used.

Ian

 

[Ian Grant]

Well, we have discussed the fact that with modern, high iodide films, the iodide developers have less effect than on older films, so lets throw that idea out. The Crawley formulas may have to be redesigned for modern films.

PE

The reason the iodide in a couple of Crawley formulae is irrelevant, and has little or no effect, is because modern films have a far higher level of Iodide in the emulsion anyway. So the formulae work fine without it.

Ian

 

[Photo Engineer]

Ian;

Removing the iodide is a redesign. It removes a component that does not work with modern films. AAMOF, color negative developers contain a minute quantity of Iodide, probably damping out this effect and allowing the DIR inhibitors to do the entire job. An analogy to redesign or design of a developer for a specific product.

PE

 

[Ian Grant]

Ian;

Removing the iodide is a redesign. . . . . . .

PE

Not in the way Crawley wrote about FX-1 & FX-2 etc. This was a particularly European area of research etc.

In FX-1 (1961 version of the formula) Crawley is adding 0.0015 gms/litre Potassium Iodide. In FX-2 we have similarly low levels of Pinacryptol Yellow.

Any significant change in the Iodide level in an emulsion tips the balance completely. So OK the formula calls for a homoeopathic amount of Iodide with 1961 films like Pan F or FP3.

So if modern films contain high levels of Iodide then leaving a trace out isn't a re-formulation.

Kodak Harrow where involved, they devised and sold developers in Europe never marketed in the US.

Ian

 

[Photo Engineer]

Ian;

I merely went by the book there so to speak. In US law, removing or adding an ingredient effectively constitutes a redesign, as work was done to prove this change to be valid. It should legitimately have a new name as well. But, you cannot expect everything.

As for Harrow, I am not familiar with their programs at all. Our B&W division was so large and had so many R&D people it was hard enough keeping up with their work by talking to them, meetings or reading their reports. Harrow contact was, for the most part, through shared reports. Very often, reports did not trickle down.

PE

 

[Nicholas Lindan]

iodide from table salt work as an inhibitor (like in the fx-1 formula)?

I thought that at one time. But the amount of iodide from using table salt is some 1,000 times the amount in FX-1 (I don't remember the real number, but it was way too much - enough to inhibit development all together).

 

[Christiaan Phleger]

So X in Microdol-X is the mercaptan. Awfully nice that its sequestaring has that dual function. Takes care of the possible water quality variable and helps out with the Dichroic fog on the silver, hey, what's not to like? That's a good formula, Microdol-X.

 

[Photo Engineer]

Well, I am not positive that is it. Probably, but not certain from other patent information.

PE

 

[lensmagic]

What is so bad about dichroic fog? Whether contact printing or enlarging, how would dichroic fog harm the image on the print??