Discussion in 'B&W: Film, Paper, Chemistry' started by Ian Grant, Jun 10, 2008.
What are the essential differences between these two Kodak developers ?
Salt instead of what ?
I'm well aware that Microdol-X and Perceptol use Sodium Chloride in quite significant qualities. Ilford wrote about using Ammonium Chloride in developers back in the mid 60's.
A&T in "The FDC" say that MX has the addition of a "weak anti-silvering agent". Benzophenone is their guess.
Apparently, salt was already in the original Microdol.
Perhaps only your local PE knows for sure.
Jim, what about Microdol. The literature I've seen in the past always said Microdol-X was silver solvent free, and because the silver solvent in Microdol caused dichroic fog with modern films.
The reason for asking is that in 1961 Kodak UK released Microdol stating that it was a Silver solvent replacement for DK-20 which of course contained Thiocyanate as the Silver solvent.
IIRC, the addition of thiocyanates and chlorides was not the only choice, that raising the amount of sulfite would have provided similar solvent properties. But it was desirable to keep the pH low, and adding the salt was the better choice.
In the '30s, '40s, and '50s ( as seen in Lowe's commentary on his developers like E-12 and E-20 ) it was understood that individual testing was necessary to find the right amount of thiocyanate to add to a developer, changing it from a FINE GRAIN developer to a VERY VERY VERY FINE GRAIN developer... without causing fog.
This was easy for the APUGGER Crafty types of the day, but not so easy for 'off the shelf users', so Kodak replaced their DK-20 (similar to D76+thiocyanate) with D-25 (D-23, but working very slowly to maximize the solvent action of the sulfite). When it was shown to cause dichroic fog in some EK film, Microdol (D-25 + NaCl) was born. It was tweaked again to make Microdol-X. Troop speculates as to what was done. Troop also suggests D-25 has been more successful in some cases than Microdol X. (Oops, Jim has been here already... yes, what HE said !)
Different film/developer combinations may or may not cause dichro fog. And a developer that caused Dichro fog in the last generation of film might NOT have a problem with the current generation.
While it is advantageous for Kodak and Ilford to compound developers which cause no problems for their current films, it is not much trouble for us to test the thiocynate method. What is to be gained over Microdol X ? Full film speed for one, higher acutance, AND finer grain.
Ian, maybe I'm reading between the lines a bit, but here's the quote from the book: "...it consists of D-23 with the startingly simple addition of a small amount of salt. "This is the 'homey' secret behind Microdol and Microdol-X".
I'm seeing that salt was in Microdol to begin with???
Ian, P.E might be able to help with this in more detail, but you can search the MSDS from Kodak`s site which might be of some use.
Microdol-X is rumoured to include an anti-stain agent which helps to prevent dichroic fog. http://www.kodak.com/eknec/PageQuer...-locale=en_GB&pq-locale=en_GB&_requestid=9180
Also, visit `Google-Patents` and type `Fine-Grain Developers` into the search box.
Keith, FYI: bis(4-hydroxy-N-methylanilinium) sulphate (from the Microdol-X MSDS) is a synonym for Metol
Keith, I've read the relevant Patents, plus more data that's not online. I'm intrigued by what was in the 1961 press releases for Microdol and then the reformulation again to Microdol-X. Not all Kodak materials were identical in the US/UK or even Canada for that matter, similar in a way to the German Agfa and the US Agfa-Ansco products.
Tri-X differed depending on which country it was manufactured, and data was published for US/UK/Canadian films3, they behaved slightly differently.
Pepper? Just kidding.. I for one will be following this thread, I like MDX but wish I could get back that extra stop.
You can get back that stop by diluting 1+3, but you will lose some of the fine-grain effect.
Tom, yes I am aware of that. In another thread, it is mentioned that Kodak `Elon` is the acid salt of Metol, hence the `Bis`.
Jim, I should have read this post before sending my first post, sorry for that.
Regarding the effects of Sodium Chloride on a Metol -sodium sulfite developing solution of low activity: See Grant Haist pages 378 and 379 of Modern Photographic Processing, Volume 1.
Separate names with a comma.