Yesterday's post about under-developed negs resulting from developing too many films at one go in an insufficient amount of D76 stock solution was, with hindsight, as clear as mud. I wrote about this "feature" of D76 from memory and thought I'd better check to see if I was on the right track or spouting forth badly remembered drivel.
Just for a change, I was almost right - I think. I've never really been a hardcore D76 user but did get through a reasonable amount of the stuff about 25 years ago. I then discovered dilute Perceptual and Barry Thornton's two-bath and was happy for a while with those. So the tendency of D76 to wimp out when asked to do much in the way of development was not exactly fresh in my mind.
The developer isn't particularly powerful and I had in mind that Kodak had recommended using a minimum of something like 250ml of stock solution for each 35mm or 120 roll. Using it as a one-shot 1+1 mix really means, if you're following the company's advice, that you should only develop a single roll in at least 500ml of solution (250ml stock and 250 ml water). In the case of a Paterson tank, just using the required 300ml to cover a 35mm film would mean that only 150ml of D76 stock was in the tank. I remembered (too late) Kodak saying that if you're using less than the 250ml then you should extend the development time.
The way I developed the two rolls of Tmax 400 and one of Eastman Double-X (1l solution made up of 500ml stock and 500 ml water) meant that each film had had just 166ml of stock solution instead of 250ml. I made no allowance for this through extended development and I believe this somewhat dense omission may have been the cause of the not-so-dense negatives.
A check of the internet revealed that I wasn't too far off the mark. Below is a screen shot of Kodak's advice in their official leaflet for D76. You can read the whole leaflet here.
Either way, my negs turned out under developed. I've reviewed my processing of the film which was fine so, in the absence of any other explanation, I reckon it must have been the not-so-energetic nature of D76 that's to blame. I'll develop the next roll of Tmax 400 on its own and that should at least confirm that there's nothing wrong with my batch of developer. Don't know if I'll have the courage of my convictions and give the multi reel approach another go any time soon, though.