[pure-silver] Re: Weird Film Issue
----- Original Message ----- From: "BOB KISS" <bobkiss@xxxxxxxxxxxxx> 
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Tuesday, May 08, 2012 5:06 AM
Subject: [pure-silver] Re: Weird Film Issue



DEAR RICHARD,
Please give us your take on this: I know that pin holes occur from the interaction of a carbonate (e.g. sodium) with acid, like the acetic acid stop bath, but I also thought that this we very temperature dependent. When using a developer-stop bath process, I have always processed at 68-70 F and have never experienced pin holes with the 8 different films I have used over the years. I mostly use PMK with a water rinse and this is a non issue with this dev but there are times I want the effect of other devs. I recall a student who said that I was being compulsive to insist that he process at 68-70 F using D-76 and stop bath. He said he didn't want to spend the time and money keeping his darkroom cool and cooling the solns before processing. He insisted that he could just adjust the dev times and process at 80 F or higher. Well, his rolls of 120 negs looked like they had been shot with birdshot...so many tiny clear holes, they were all ruined. A 
rather expensive lesson he will never forget.
CHEERS!
BOB
Most of what I know is conventional wisdom, here it is FWIW: Pinholes can be caused by gassing of the developer. It appears that only carbonates react with acid to produce carbon dioxide gas. This is the familiar reaction of vinegar and baking soda or an Alka-Seltzer. Developers made without carbonates do NOT produce any gas, these include D-76, which is made with borax and developers containing metaborates (Kodalk). There is some question in my mind if even carbonate containing developers can cause pinholes in modern hardened emulsions. I think this fear is a holdover from the 1920s and 1930s when emulsions were very soft. There are other causes for pinholes such as the deposition of undissolved particles on the emulsion during development. However, these cause tiny clear spots where true pinholes are actual disruptions of the emulsion. Pinholes do not seem to be a problem for prints even though most print developers have carbonate in them. Probably, if they exist, they are too small to be of significance.
Low temperatures are also a holdover from much earlier times when emulsions were very soft. This may again be a problem because many films are now made by small manufacturers using very old technology. Until about 1940 (not an exact date) the standard processing temperature was 65F. Around then it was increased to 68F because most emulsions were sufficiently hardened to withstand it. Some modern emulsions are hardened enough to take 100F processing but only some. In the old days temperatures up to perhaps 75F were considered normal but much above that, certainly at 80F, it was advisable to use "tropical" processing with additions of sodium sulfate in solutions and perhaps additional hardening. I doubt if this is necessary with films made by the major manufacturers, namely Kodak, Ilford, and Fuji, but one should be careful of films made in the smaller plants. I can't explain your students films but would be interested in what film he used. This sounds more like reticulation than pinholes. Reticulation is the wrinkling of the emulsion caused by excessive softening and by loss of the adhesion between it and the support. Reticulation was very common in the bad old days and was the main problem with high temperature processing. It is also the reason that older books recommend that all solutions be at the same temperature. Actually, reticulation is hard to produce on modern films and may take extreme change of temperature for success. I think the old advice about matching temperatures within a couple of degrees was always exaggerated but perhaps not. Note that there are other effects that can cause distortion of soft emulsions; simply the change in pH between developer and acid stop bath or fixing bath will cause mechanical stress. Again, this has not been a significant problem for many decades. Its probably safe to work up to about 75F with most modern materials and some developers recommend the higher temperatures for reasons I don't know (D-25 and Microdol-X suggest 75F, at least in older literature). This leads into an area where I have no definite knowledge: how much difference in result is there from variation of developing time and temperature if the target contrast index is the same. Its evident that diluting developer can have considerable influence on its characteristics (grain, sharpness, effective film speed) but dilution is one way of compensating for the excessively short developing times gotten with higher temperatures. D-76, whatever its faults, remains one of the most reliable and predictable developers in existence. 


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk@xxxxxxxxxxxxx 
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