more sheets in the tray, how much more time?

hi there

i have a question for you sheet film in the tray processing gurus out there.
when development times are given for sheet film/tray processing,
typically how many sheets is that for?
my standard is 8 sheets and it is ok ( i process a bit longer and DBI )
is there a general rule " x seconds/ film beyond 8 sheets " or something
like that?
when i used to deep tank in hangers, i never had questions like this,
seeing all the hangers did their thing at the same time -
seeing i am shuffling the film in a tray, it takes longer to cycle through more sheets,
so it will take more time to develop more film ...
thanks in advance for your advice

john

John -

I've never seen a hard rule, but it seems to me that logic would lead to two conclusions:

1. I suspect that there is an implied assumption about the amount of active ingredient per square inch of film surface area in the developer solution in any time-temperature equation, and if the surface area of the film is such that this assumption is violated, it would be necessary to extend development to compensate. On the other hand, if the volume of liquid provides sufficient active ingredient per square inch of film for a larger number of sheets of film, then extending development would not be needed.

2. One of my concerns with the shuffling method of processing film in trays is that as the number of sheets increases, the time required to shuffle through the entire stack of film increases. Therefore, in a given block of time, the amount of agitation received by individual sheets will decrease as the number of sheets increases. As a result, if the basic development time doesn't change, increasing the number of sheets processed at a time should lead to a reduction (probably slight) in contrast. And taking this further, then it makes sense that the development time might have to be increased slightly to achieve the same end contrast.

I usually think of this differently. If I'm only doing two or three sheets, I slow down the agitation, so maybe I'll cycle through the stack every 15-30 sec.

As far as the issue of the volume of solution goes, if you don't have enough solution to develop as many sheets as you have, you probably don't have enough solution to shuffle effectively.

Here's how I'd tackle this; Divide how much developer you're using for 8 sheets by 8 and this'll give you how much developer is needed per sheet of film. Then I'd multiply that figure by how many sheets I want to develop to find the volume needed. Also, making sure I can shuffle through the stack once every 30 seconds, and ensuring the first one in is the first one out pretty much covers it, I think.

How many are you wanting to do?

Murray

hi again

i have sucessfully processed 28 sheets of film in a tray ( 8x10 tray with 2L of
solution ) i didn't really pay attention to the time when i finished
seeing i would shuffle through all of them, and then look at a few under the
green safelight maybe it was 2 mins longer than my standard 8,5 mins
( for 8 sheets of film ) ? ... i guess i get bored just standing there shuffling film
yeah, i know 28 sheets of 4x5 film processed all at once is certain-suicide,
but sometimes i want to get it done with as fast as possible... LOL


i wish i had the time, energy and attention span to do a while bunch of
film/developer tests, and that way i could post my results for everyone to see ..
but seeing i have none of them ( especially the attention span! )
i was just looking for a shortcut

its good to hear what others think + do, and gives me a little
bit to ponder as i shuffle through another 8 or 10 sheets of film
in 10 minutes <sigh> ...

thanks for the responses so far!

john

ps. i usually put the film in a water bath, separate them, shuffle them in there
for about 1-2 mins, and then the whole stack goes into the developer at once.
i shuffle right away, and try at least to remember which one was on top ...
when it comes time to take them out of the developer, like i put them in, they
all come out at once and go into a water bath to separate, and make sure i didn't
leave one orphaned ( or worse! ) and after a few cycles in the fix ...

Hi John,

My dad was a chemical engineer...can you tell? I'm far from being a Guru and whatever you're doing is sure working as evidenced by your photography.

I saw an interview with the creator of the comic book series Spawn, who said there's two kinds of people; those who tippy-toe to the edge and see if it's ok to jump, and those who run hell bent over the edge and figure it out on the way down. I don't think you've got a tippy-toe bone in your body!!!!

Keep on jumping...the view must be great

Murray

jnanian said:

hi again

i have sucessfully processed 28 sheets of film in a tray ( 8x10 tray with 2L of
solution ) i didn't really pay attention to the time when i finished
seeing i would shuffle through all of them, and then look at a few under the
green safelight maybe it was 2 mins longer than my standard 8,5 mins
( for 8 sheets of film ) ? ... i guess i get bored just standing there shuffling film
yeah, i know 28 sheets of 4x5 film processed all at once is certain-suicide,
but sometimes i want to get it done with as fast as possible... LOL

Click to expand...

WOW! 28 sheets! holy cow!
another option may be a daylight tank. iuse a doran tank and i have no problem with uneven development. it holds 12 sheets. sometimes i do two tanks at once. very easy...i stand in the light and surf the net between agitations. i usually agitate every 3rd min. hc110 dil g.
sorry i can not help with your tray question. i usually use 4 trays with about 4 sheets/tray. you could try this. other wise i scratch the hell out of them.

hi murray -

yeah, i don't like heights, unless i am freefalling

john

hi eddie

i have seen daylight tanks, but never used one ...
i have an FR tank or 3, used it once, but never again ... not because of
uneven development, but because it took more chemistry than i had on hand

i guess i have a good system, and shouldnt' fix it unless it is broke.
so, i'll just keep using the green light

thanks everyone for your suggestions and input.

john