curiosity about two baths development .

because the development in two baths It exploits well the speed of the film ?
because almost all traditional ones eat sensitivity?

Many thanks ...

It depends on the composition of the two bath developer.

https://www.photrio.com/forum/threads/diafine-recipe.49999/
You may brew your own Diafine substitute or buy Bellini Duo Step.

I have been using two bath developers for a long time.
it's just a curiosity to know technically the differences of the process that lead the development in two baths not to decrease the speed of the film.

IMO, best speed is obtained using carbonate and sulfite in the part B bath. The sulfite uncovers latent image specs and the carbonate may (it is not definitely known) complete the development before it diffuses out of the emulsion.

schyter said:

because the development in two baths It exploits well the speed of the film ?
because almost all traditional ones eat sensitivity?

Many thanks ...

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I started to use a 2 bath development mainly because just plain old coffee was too slow and took forever, so I sped up the process by
skinny dipping either ht film or the prints in a faster developer just to get it started, and then I finished it up in the coffee. Its probably a figment of my imagination
that it made a difference and isn't the same as a water bath like when using amidol and a silver chloride paper... do you use a 2nd developer when you are using your
nuesol developer ( I mean Jnùsol FM . ) ?

jnantz said:

... do you use a 2nd developer when you are using your nuesol developer ?

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No, Jnùsol FM it's single bath developer (film & paper).
however it might be an idea !

You could probably tailor a two-bath developer (somewhat) to suit one particular emulsion. Do bear in mind that none of the major manufacturers offered 2-bath developers, nor recommended them in the post-WWII era - and there is no doubt that they'll have tested 2-bath development to levels of image structure/ quality that your average home-developer-taster can't even get within touching distance of.

schyter said:

No, Jnùsol FM it's single bath developer (film & paper).
however it might be an idea !

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ahh I mixed up the name sorry about that !
yea ... might be fun
I got my inspiration from Divided D23 ( DD23 ) years ago. I had been using Ansco130(and later Dektol/D72) as my primary film developer and got addicted to juicing the bean and though .. hmmmm. DD23 uses a borax bath ( or something like that ) to do something useful, I wonder what would happen if I used caffenol ( that has a lot of ) Sodum Carbonate, I wonder if it will do the same thing ... and well, there you go. I use it with prints too, the same way I would use a depleted bath to let the midtowns even out and the fresh bath to boost the contrast ... but I use either of the same 2 developers mentioned previously and CaffenolC .. the caffenol I use is from home roasted Sumatra Robusta eyeball measured other ingredients and a speck of either D72/Dektol or ansco130, depending on what I have lying around. been my GO TO for 15ish years..
have fun!
John

Lachlan Young said:

You could probably tailor a two-bath developer (somewhat) to suit one particular emulsion. Do bear in mind that none of the major manufacturers offered 2-bath developers, nor recommended them in the post-WWII era - and there is no doubt that they'll have tested 2-bath development to levels of image structure/ quality that your average home-developer-taster can't even get within touching distance of.

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You underestimate major manufacturer Tetenal who sold Emofin but probably discontinued it because it contained PPD.
An estimate of the formula is known and it it should be possible to get good results leaving out the PPD, I did not try it:
https://www.photrio.com/forum/threads/microdol-x-replacement.46346/page-8#post-669467

Two bath developers, at least for current films, are a special purpose tool and not a substitute for the regular single bath developers. Major manufacturers are generally not interested in low volume special purpose tools that can't be priced at a high premium.

Raghu Kuvempunagar said:

Major manufacturers are generally not interested in low volume special purpose tools that can't be priced at a high premium.

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No - if they produced a meaningful, genuinely measurable and visually identifiable (in a double blind test) improvement over a status quo product, the major manufacturers would have put the effort in - especially for a product that purports to make things easier/ better for photographers with poorer process control (ie amateurs). That they didn't suggests that the methodology fails technologically (bad balance of relationships between sharpness/ granularity/ latitude/ tone curve shape/ shadow speed/ 'coverage'/ evenness of processing etc) and/ or visually as a consequence of the above relationships going out of kilter with each other. Which isn't to say that products that might fail similar testing today in some aspects (Rodinal) remain on the market because they are strong sellers with very high levels of name recognition - in some ways precisely because of those self-same failings. It's just that two-bath developers seem to never be as good as a competently process controlled single bath developer.

Alan Johnson said:

You underestimate major manufacturer Tetenal who sold Emofin but probably discontinued it because it contained PPD.
An estimate of the formula is known and it it should be possible to get good results leaving out the PPD, I did not try it:
https://www.photrio.com/forum/threads/microdol-x-replacement.46346/page-8#post-669467

Click to expand...

Latterly it seems to have had CD-1 in it - which could probably be fairly readily replaced with CD-4 (but not CD-3) if experimenting along that route. There are better ways to potentially get a developer that utilises the safer PPD derivatives to full effect, rather than something that looks suspiciously like a divided Beutler variant with added PPD.

It suggests that Tetenal likely did very little to upgrade Emofin over the years. Overall, Tetenal's biggest strength was not in applied research (based on new fundamental knowledge), but in the ability to make at all sorts of batch sizes (unlike Ilford or Kodak's packaged chemistry plants, apparently). Their most recent developers suggest they've been beneficiaries of this outside knowledge as they appear to have eliminated most of the more 1940s/ 1950s technological approaches in favour of ones that suggest an understanding of the extent to which developer technology has moved along since Beutler's era - such as Phenidone (and derivatives) being found to be sharper than Metol.

Lachlan Young said:

No - if they produced a meaningful, genuinely measurable and visually identifiable (in a double blind test) improvement over a status quo product, the major manufacturers would have put the effort in - especially for a product that purports to make things easier/ better for photographers with poorer process control (ie amateurs). That they didn't suggests that the methodology fails technologically (bad balance of relationships between sharpness/ granularity/ latitude/ tone curve shape/ shadow speed/ 'coverage'/ evenness of processing etc) and/ or visually as a consequence of the above relationships going out of kilter with each other.

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Do you have any evidence, even anecdotal, on major manufacturers trashing the potential of two bath developers based on their own research? Haist thought it was worthwhile to discuss two bath development in his book. I didn't see him drawing any conclusions like you in his book. In fact he writes, based on Kodak's own research that "a given volume of D-76 developer has been found to provide more uniform development and less loss in emulsion speed during exhaustion when divided into two baths than when used as a single bath." Yes, these conclusions were drawn for films of bygone era and the advances in emulsion technology might have closed the gap. But where is any evidence from scientific literature that two bath developers are fundamentally worse than a single bath developer like D-76?

Lachlan Young said:

. Their most recent developers suggest they've been beneficiaries of this outside knowledge as they appear to have eliminated most of the more 1940s/ 1950s technological approaches in favour of ones that suggest an understanding of the extent to which developer technology has moved along since Beutler's era - such as Phenidone (and derivatives) being found to be sharper than Metol.

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Can you expand on this with examples from their product range and your source for this information?

Raghu Kuvempunagar said:

Do you have any evidence, even anecdotal, on major manufacturers trashing the potential of two bath developers based on their own research? Haist thought it was worthwhile to discuss two bath development in his book. I didn't see him drawing any conclusions like you in his book.

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At best he provides a literature overview in that segment - and no current analysis. You have to be careful reading Haist because as much as he provides an overview of processes, he meticulously avoids (other than hinting at) commercially sensitive technology/ knowledge that only becomes clearer when you read alongside later work - such as Ron's (who was one of the peer reviewers/ censors of Haist's book) - and other patents, academic publications/ papers, theses of the era. It's a book written for a reader wanting a large-scale overview of the processes at a fairly good technical level, not necessarily for someone who's 'skilled in the specifics of the arcane art' - if it was written at the latter level it would probably have been 10x the size, and probably unpublishable at the time because of the level of commercial sensitivity - there's not much discussion of the use or exploitation of inhibition effects, for example - which we now know to have been under intense R&D at the time. You also have to remember that the culture Haist's book came from didn't necessarily want to tell third parties without large research staffs how to improve their competing products (and those with significant R&D staff had likely pretty quickly worked out what Kodak was doing anyway). There is no doubt that a two bath system can potentially provide a decently optimised development system for a given emulsion/ contrast index - but so could a monobath system, and that seems to have been where Haist saw greater potential. There's nothing particularly 'magical' about 2-bath developers, and the increased complexity of having to maintain multiple 2nd baths to control contrast rapidly becomes impractical - as opposed to simply adjusting the development time of a single developing solution - and/ or using emulsion based approaches to dealing with contrast variance (variable contrast papers for example) - all of which are far more universal in applicability than a 2-bath system.

Alan Johnson said:

Can you expand on this with examples from their product range

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The varying evolutions of Ultrafin for a start - which now seem to have settled down into conventional two developing-agent formulae, rather than 3. And the other ingredient choices for Ultrafin T-plus & Neotenal pretty closely reflect what most of the high-tech developers aimed at more modern emulsions headed towards.

how about. ... trying a 2 bath developer and trying a single bath developer and seeing which one one likes best ? and that way its not old information written &c by someone else but personal experience?

jnantz said:

how about. ... trying a 2 bath developer and trying a single bath developer and seeing which one one likes best ? and that way its not old information written &c by someone else but personal experience?

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You should do that with the awareness that all personal experience will be disregarded: "there is no doubt that they'll have tested 2-bath development to levels of image structure/ quality that your average home-developer-taster can't even get within touching distance of."

Raghu Kuvempunagar said:

You should do that with the awareness that all personal experience will be disregarded: "there is no doubt that they'll have tested 2-bath development to levels of image structure/ quality that your average home-developer-taster can't even get within touching distance of."

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their loss.
as they say on the shampoo bottle. " rinse lather repeat".