Tuesday, September 27, 2011

TCB - Trouble In Paradise

I've been playing with p-aminophenol developers again.  I found that parodinal + ascorbate + borax (RCB) makes for a fine grain full speed developer.  I also found that substituting ascorbate for sulfite in parodinal works too (TCB).  However, doing side-by-side tests as a one-shot developer, I find that I need twice as much ascrobate-parodinal as I do sulfite-parodinal to get the same level of activity.  This bugs me a bit as ascorbate-parodinal is half as efficient as sulfite-parodinal which means I'm wasting a fair amount of  ingredients.

Activity levels aside, the visible difference between the two is the formation of long needle-like crystals in the sulfite version and not in the ascorbate one.  I don't know what the crystals are but if they are p-aminophenol that means that sulfite-parodinal is super-saturated while ascorbate-parodinal is not which would explain the difference in activity levels.  Could it be that the conversion of acetaminophen to p-aminophenol needs sulfite to complete?

I have nothing against sulfite and it's something I stock anyway as I use it in my fix.  I'm just curious about the chemical process here so I can better understand what is going on.  I am not a chemist in any way so I'm hoping to learn from others with more knowledge about this.


Thursday, September 15, 2011

Phenidone-C Divided Developer - Strangeness

I've been toying with the idea of a Phenidone-C divided developer akin to divided D-76 or Diafine.  Based on my experience with Phenidone-C so far, I propose the following formula:

Part A
Ascorbic Acid - 80g
Sodium Bicarbonate - 60g
Water - 750mL (make sure all is dissolved and effervescence stops)
Phenidone - 1g
Water to make 1L

Part B
Sodium Hydroxide - 1.45g
Borax - 6.92g
Water to make 1L

Agitate for 5 mins in part A then 5 mins in part B.

I did a quick test with the recipe scaled down to 100mL and use film clips to get an indication of activity.  What I expected to happen and what actually happened really surprised me.  I expected there to be no visible evidence of development in part A while the ascorbate + phenidone soaked into the emulsion and expected all the development to be visible when in part B.  To my surprise, after about 1 min in part A I noticed a slight darkening of the film and after two mins it was nearly black.  I thought I was going nuts here as everything I read and experienced showed that you need a higher pH to get decent activity out of Phenidone-C.  The time in part A is within range of a normal 8-10 min developer.  I thought I may have contaminated part A and increased the pH so I checked it with a calibrated meter and it showed 7.2 ... about what I expected being near neutral.  Now this is confusing ... ascorbate developing at a pH of 7.2?  I still don't believe it but I ran the same test 3 times with the same result.  I have no idea what's going on here and cannot explain it.  On the plus side I'm thinking with the really low pH this very concentrated phenidone-c-bicarbonate mix could be an extremely fine grained re-usable developer.

On one hand this really complicates my idea for a two part phenidone-c developer but on the other hand I may have stumbled across a new unexpected developer.

Next step is to actually process film instead of test clips to see real world results.  I propose two initial tests, one with just part A for 8 mins and one with part A for 2 mins and part B for 6 mins.