Ah. OK. Sorry. I thought it was PQ. Thanks though
They might have though.
Using it as a second developer sounds kind of interesting then... did you ever do that, if so... did you use regular dilutions and times?
B&W reversal: Thiocyanate or Thiosulfate
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They might have though.
Using it as a second developer sounds kind of interesting then... did you ever do that, if so... did you use regular dilutions and times?
I'm curious if you had tried PEG as an accelerator. I know you showed me an article in the thread I posted but it seem like adding just PEG itself lowers Dmax. Now with the 3rd lockdown in the UK it's going to be hard to get access to the lab to get my hands on some PEGs. My plan now is to just clip off film leaders for TMax400 and try it with the 1.3x Microphen I have but adding different percentage of sodium thiosulfate or PEG or a combination of both. I would be interested to know if you know a PEG percentage to start experimenting with.
I've done this many times. I just add a couple of spoons of my pyrocat-pc concentrate to 500ml water that already has a spoon of potassium carbonate. It gives nice toned positives after about ten minutes of development.
That's what I too think. And hence puzzled by the concerns expressed about reduced effectiveness of Dietrich's first developer on reformulated TMax films.
I’ll try this with Pyrocat-M at some point. Guess it will work pretty much the same way... thanks
Here's the Agfa patent for the first developer: https://patentimages.storage.googleapis.com/f7/bd/9d/6a0a4f9307d9d8/US6350563.pdf
I read through it and this is the relevant chart:
But from reading it, it does not sound like adding the PEG alone is enough:
"Surprisingly, it has now been found that the use of 5-methylbenzotriazole in combination with polyglycol P400 and hydroquinoneSulphonic acid resulted in the desired gradation curve and in usable image results."
Regarding what that means:
"P200 and P400 resulted in the lowest loss of maximum density, so that P200 and P400 appeared to be the most suitable for this developer. All further investigations were therefore performed using P400 as the development acelerator.
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You're reading the wrong parts.
You want the 'Commercially Available First Developer Containing Hydroquinone' recipe. Ignore the HQMS ones derived off E-6.
The rest is much like all those peroxide bleach patents, where they are defensively patenting research that while it may never have worked well enough for commercialisation, it protected research paths that might be productive in the future. Thus, while the bleaches might not be much realistic use, the disclosed developer recipes for RA-4 and C-41 are of interest - as are the layer structures of C-41 films. It's the same with Ilford patents that disclose the recipe for 'Multigrade' developer alongside other work which never made it to commercial fruition.
Way back in Lockdown 1... I acquired about 100g of PEG-1500 and was planning to make the Agfa FD & test it against some hypotheses I had - then I found myself busy with printing work, Adox announced their reversal kit & I put everything on the back burner for a bit - along with ideas of trying the PEG in other developers - wasn't helped by having a large quantity of Delta 3200 on hand, which for all its merits, isn't a great choice for reversal processing! As it is, it's given me a bit of time to consider what the developer is actually doing.
Here's the recipe for 1 L as disclosed in the patent linked in relistan's post (edited lightly to make it easier to read):
4.5g Hydroquinone
11.0g Potassium Sulphite
41.7g Potassium Carbonate
1.5g Sodium Carbonate
5.5g Potassium Hydroxide
2.0g Nitrilotriacetic Acid
1.6g Potassium Bromide
67mg Benzotriazole
3.8g Metol
0.4 ml Hydroxyethane-Diphosphonic Acid (Etidronic Acid/ Dequest 2010)
1.2g Polyethylene Glycol, molecular weight 1500
2.0g Sulphuric Acid
made up with water; pH 10.2
FD time for Scala 200x (because what else in an Agfa patent is 'A commercially available black-and-white reversal film, e.g. that of film speed 200 supplied by Agfa-Gevaert AG'?) is cited as 6 minutes - which is what Scala 200x runs/ ran at in Scala processing.
Several things I note - it mostly uses potassium salts, apart from a small amount of Sodium Carbonate - not sure why yet. Possibly something to do with forming a specific HQMS salt in solution. One of the key things not given is a mixing order.
The molar ratio of M:Q is in the order of 1:4 - as opposed to many universal/ paper developers where it's often closer to 1:10 - D-76 is about 2:15 and DK-50/DK-60a are about 1:3 (I think). There is obviously some significance here, but again, it doesn't give much away.
The Nitrilotriacetic Acid (the one tricky bit to get hold of) and the Dequest 2010 I had previously dismissed as insignificant and related to dealing with water quality variance - but I now wonder if the Nitrilotriacetic Acid (at least) isn't playing some sort of role in controlling the silver ion concentration in the developer. Note too that the disclosed second developer is PQ based and uses EDTA (I would not be surprised if it wasn't very close to Neutol or similar) - which suggests that if a phenidone and EDTA could have been used in the first developer, they would have been. So there have to be very specific reasons for using Nitrilotriacetic Acid and Dequest 2010.
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Interesting, I see what you mean. I guess they are comparing the new developer against the one they already commercialized and that explains why it's not as good.
I am no expert, but isn't it easier usually to dissolve potassium salts? So maybe some kind of solubility issue?
Yes, I think that's right. There are a bunch of bleach patents that I have read that use various carboxylic and aminopolycarboxylic acids to bond with silver ions. EDTA is specifically used in some Kodak patents, others refer to different members of the family.
I have a suspicion that it may have been the outcome of a bean counting/ process improvement/ marketing instigated exercise to see if Scala could be run using an E-6 machine/ chemicals already being made in much larger quantities.
That's the seemingly obvious answer - but there are plenty of ways to do it without using both Na & K salts - that's what's puzzling me, especially as it's a tiny amount of the Sodium Carbonate. Normally you'd switch over to Potassium salts for solubility and eliminate the Sodium ones. The only reason I can see is that some Na+ ions were needed for some reason. Unless it's something to do with the Nitrilotriacetic Acid.
I sent Ilford an email a few days ago where I asked if there was a specific reason as to why they chose thiosulfate over thiocyanate... I havent heard from them, but when they do I'll report back.
@Alessandro Serrao: Tmax 100 seems to excel in DR5 process without any speed loss and without needing any halide solvent.
Very simple reason why: it's the most obtainable silver solvent that won't release HCN on meeting the permanganate bleach. KSCN was replaced by DTOD in Kodak's cinema reversal process for that reason too.
OK. What about before permanganate bleach was used... why didnt they use thiosulfate then? It seems to me that because of the permanganate bleach this isnt really a choice... but if there is a choice thiocyanate is preferrable?
Thiocyanate seems to be the preferred halide solvent going by old formulas and Haist. There's a good technical explanation of the role thiocyanate plays in the first developer in Haist volume 2. Worth reading.
Yup. I did
And as I understand thiocyanate is better as it is most active where it is most needed (in the highlights)... and I assume this is still the case with todays films...
Dichromate bleaches don't seem to have the potential to release HCN from KSCN in the FD. There are lengthy threads on here that cover the chemistry in detail.
The other thing to consider is that KSCN etc may not be as good a choice today - there's a long list of development accelerators that can effectively do the same thing - and the 'success' or otherwise of some reversal processes may be because some of these accelerators are also being used as surfactants in the emulsion (or for that matter as development accelerators). The strange patterns that people report appearing on film processed in tanks that are still contaminated with wetting agent occur because the surfactant is having an acceleration effect on the development rate.
This weekend I intend to try first developers with the things I have on hand: propylene glycol, ADOX Adoflo, Kodak Photo Flo to see if there is anything noticeable. Not sure exactly how much to add, so will mess with it a bit. I remember from Mark Overton's Mocon thread that propylene glycol was working as an accelerator when in enough concentration.
I'd start at 1ml/l and go up or down from there. From the literature, it doesn't seem to take a lot to have a significant effect - and not all are going to be accelerators with all developers. I suspect there might be an improvement, but not a significant one - you may need a higher molecular weight PEG or derivative.
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Haist says thiocyanate is also a development accelerator and an incorporated development accelerator in some films.
Some combinations of accelerator and developer produce undesirable level of base fog thereby diminishing the DMax and possibly reducing the speed. Even Agfa-Gavert patent had some combinations that didn't do well and needed special restrainers.
It increased base fog as well when phenidone was used as recounted by @albada in a different thread today.
Yes - point is that it's one of several options, which may improve or worsen results. I've seen it crop up in emulsion finish steps too. Remember that Haist's book was carefully gone through (by Ron amongst others - he's the 'Rowland Mowrey' in the acknowledgments) to excise anything commercially sensitive at the time of publication.
Again, yes - that's the problem: you have to balance the accelerator/ solvents enabling fast access to the silver against them ramping up the development rate so drastically that they cause general fog. And as the Agfa researchers found, you end up needing specialist restrainers.
One other note/ data point, TMax 100 has to be coated with an unusually thick gelatin topcoat to regulate development rate by slowing diffusion into the emulsion - otherwise it would develop way too fast to be controllable. This may well help it to develop fast/ well enough to produce a good reversal without too many additives. The TMax direct positive kit used an unspecified PEG, which would speed up the diffusion too by increasing gelatin swell.
Yeah, thanks I know about that already because I regularly use PC-Glycol with phenidone. I found that you have to add restrainer to keep it from fogging.
Thanks, good starting point!
I used a modified Ilford reversal process back then, it was in 2004.
I used half the permanganate Ilford advised and used Ph down powder for the sulfuric acid (55g/lt). It worked just as fine.
I didn't questioned the use of hypo: it worked out of the box.
And it worked very well also on an eFKe 100 roll.
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