Adjust D76 dev time for Tri-x at higher temps?

naugastyle · Nov 27, 2010

Hi, having trouble figuring out how to adjust D76 times for the temps I have here. I am living in a fairly basic place and do not have access to a refrigerator. Room temp is 80 degrees. So for NP1600 I've been using the times from the data sheet and results are good, but Tri-x data sheet from Kodak only goes up to 75 degrees. I'm just not positive of the formula for how the new times are determined.

It looks like you subtract 5% off the time for each higher degree Celsius, but that doesn't seem totally consistent because 21C/70F should be 9 1/4 (1+1) in that case. Can I assume 7 min 1+1 for 26C/79F or would that be way off?

JamesMorris · Nov 27, 2010

Try extrapolating this chart:
http://www.digitaltruth.com/devchart.php?doc=timetemp

If the dev time goes below 5 minutes, dilute the developer more.

I've been seeing water temps up to 26C in Sydney, and there's a chart in the darkroom which goes up that high, but I don't have it with me.

On a side note, I was just reading about a developer called 777, which was legendary for being usable in the field like this, which you can still get or make up.

dehk · Nov 27, 2010

Just a reminder. Its recommended to dev film over 5 minutes or it may result in uneven development.

naugastyle · Nov 27, 2010

Thanks. Not quite sure what to make of the MDC page, as it gives about 7 min at 24C, but the Kodak sheet has that as 7 3/4 min. And at 18C it would be 12 min, when the data sheet says 10 3/4 min. Making 26C, which is what I have here, close to 5 min which seems like a big jump compared to the rest of the data sheet.

Urgh. I may just have to go for it at 7min as that sounds more reasonable than this, and try to decide if it looks overdeveloped. I appreciate your help!

Rick A · Nov 27, 2010

Just use a tempering bath to bring your chems down to a reasonable temp. An 11x14 tray with some water chilled with ice chips is all you need.

bdial · Nov 27, 2010

...water chilled with ice chips...

No fridge...

But Rick's suggestion is still good though, hopefully your cold tap water is a little lower than 80, or you may be able to put a jug of water next to a window to cool it some and use that to dilute the developer to 1:1 and for the water bath.
The vendor times are the best source for starting points, the times in the Massive chart are what lots of other people have ended up with after their own experiments. Their times may or may not be valid for you.
If you can't get your temps much lower, your best course is to do some of your own experimentation. As suggested, extrapolate from the times you have available and run a test roll. If it's over developed, lower the time or increase the dilution and try again.

naugastyle · Nov 27, 2010

It's the same temp outside as inside, even at night when it feels cold to me without sun, it's not much below 80 degrees. My profile still says I'm in Brooklyn but I'm actually in a small town in Thailand until mid-April. Umm...when it will likely be 90 inside, eek! Not in a real house, which is why I don't have a fridge, and although the tap water feels frighteningly cold to me when I shower, I measured it at 80 as well. I've actually been using bottled water though, the tap water isn't safe for drinking so I don't know what exactly is in it.

Thanks for the advice. I will test it out today, maybe at somewhat below 7 min...will look at the chart again to decide.

Lee L · Nov 27, 2010

Results of regressions I ran last spring on time vs temp tables from Kodak Publication J-1:

Tri-X
degrees in Fahrenheit

D-76 new time = old time * .9505 ^ ( new temp - old temp)
D-76 1:1 new time = old time * .9694 ^ (new temp - old temp)

Lee

Dave Martiny · Nov 28, 2010

I can feel your pain. I live in Phoenix, and in the summer, our tap water comes out at a refreshing 95F. Even so, for the sake of consistency with my winter developing with Rodinal, I use ice in a water bath to cool my chems to 68F.

If I were you with your current circumstances without ice, I would switch to FP4+ @ 250 in Diafine. I have used this with excellent results, very similar to Tri-x in D76 1-1. Diafine is a 2 part developer that is essentially temperature and time insensitive and can be used anywhere between 75F and 85F. It works well with a variety of films and gives many of them a noticable speed boost, such as Tri-x up to 1250-1600. It comes as a powder in 2 cans, and you re-use it without replenishment. The stuff has a ridiculously long shelf life (as in years) and will do dozens of rolls to the gallon.

Regards,

Dave

msa · Nov 28, 2010

While using some ice is definitely a good idea if you're beyond 80F, I used to tank process Tri-X between 75 and 80 all the time. I've developed a LOT of Tri-X in warmer than 'suggested' temperatures but try not to do so above 80, but I will do it at 80. Used to live in an apartment in CA without air conditioning, and even with it, I have to be a little flexible about process temperature here in Phoenix.

Stock solution strength you get slightly below 5 minutes, and if you go that route you need to have your stop laid out before you start, and be prepared to work pretty quickly. I've done this a lot when in a hurry, and it does work, but if you've got time, you might dilute to 1:1 (working strength D-76) since that'll give you enough process time both to be safe, and so you don't have to rush.

Adjust D76 dev time for Tri-x at higher temps?

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