Is 80f too warm to develop?

[koraks]

that is where they start to work.

No, not really. See #10. I think 20C was chosen because it's close to room temperature.

 

[Ian Grant]

Temperature of 68f [20c] was set as the threshold for B/W as that is where they start to work.
above that it is a matter of how one stander the process.

18ºC / 65ºF was the recommendation in the first Manual of Photography (Ilford) in 1899/90. Later that went to a slightly more practical 20ºC / 68ºF.

The reason is simple, at higher temperatures early Gelatin emulsions were prone to sell more and very prone to processing issues, frilling off glass plates, excessive reticulation, because they were unhardened. Over the years films & plates slowly became better hardened, but good hardening was really only introduced in 1968 with the introduction of FP4 & HP4, and Kodak etc followed with their equivalents.

Kodak research showed that film development temperature did not have any effects on grain size, as Ron Mowrey (RE) posted some years ago. However, temperature variations between baths even with hardened films could cause what Kodak called surface artefacts, others call it incipient or micro reticulation. This leads to more apparent graininess in pints, it has been known about since the mid 190s and can be overcome by wet mounting. There was a BJP article in 1926 about wet mounting.

Modern Kodak films say they are optimised for scanning, this is actually greatly improved hardening. When digital minilabs were first introduced Kodak colour films were scanning with increased graininess compared to optical prints, Agfa & Fuji films were fine. This was the surface of the gelatin super coat interfering with the scanning. There's a Kodak Patent covering the research into the greatly improved hardening.

When you look at modern films, it is difficult at first glance to wee which is the emulsion side, because the super coat is so smooth. Older films are quite different.

Ian

 

[DREW WILEY]

A water jacket can be as simple as a tray of water held at the correct temperature which you put your chemical containers in until they reach equilibrium. It could easily be 68F if you use any number of tricks already mentioned to cool the water down.

It also helps to use a pre-rinse in the loaded drum of the same temp, to bring its internal temp down. When you are not actually agitating the processing tank or drum, it should be resting in that tempered water tray in order to maintain the lower more practical temp.

 

[Paul Howell]

As I recall 60s vintage films had a softer emulsion and at higher temps the emulsions could and did peel off. Fast forward 60 years and emulsions are now rather hard and can take higher temps. As noted by Sirius Glass there might be an issue if overall development drops below 5 minutes in terms of uneven development time. That might depend on which method is used SS tanks and reel vs plastic tanks and reels and large the tank is as how long it takes tank to empty. I recently used up the last of my Acufine and developed Foma 400 at 3 1/2 mint in a Patterson tank without issues, that was at 70 degrees, moving up to 75 would have a 2 min development time which is too short for me. At 68 to 80 I think you are safe with most films.

 

[DREW WILEY]

Certainly not all films have firmer emulsions. Better safe than sorry.

 

[cliveh]

I never develop film at temperatures + or - 5 degrees of 20C/68F