Open vs Closed tray

[buze]

So far I have developed most of my film (4x5, and 8x10) in a Paterson Orbital daylight tank. It works great for 4x5, a bit more tough for 8x10 but overall the development times I get are consistent.
I use Barry Thornston (Metol) 2 bath and 5:5 gives me great result, and I can push to 10:5 or even 12:5 for 'alt process' bulletproof density.

Recently I equiped with IR goggles with the goal of 1) being able to tray develop and therefore do more sheets at a time 2) inspect.

I can "inspect" allright, however it turns out that using the same developer, I have to /at least/ double the times to get any density at all. 10:5 will give me an "OK" neg bu nowhere near the density I get in the Orbital.

Anyone has an idea why ? I 'agitate' by moving the neg from the bottom of the 'stack' to the top every minute or so... the temperatures are roughtly the same (Barry's is pretty consistent regardless of temperature anyway) and I really don't know why the tray development could make such a difference.

And yes, I use 940nm illumination and the eyepiece is covered...

[Darren Kruger]

Anyone has an idea why ? I 'agitate' by moving the neg from the bottom of the 'stack' to the top every minute or so...

I thought in tray developing film that you needed to shuffle the sheets and agitate constantly.

-Darren

[Harold_4074]

I'm not familiar with the Thornton developer, but you might consider whether or not you are processing the same ratio of film area to developing agent in the two methods. It is possible that you are exhausting the first-bath agent to a greater extent when tray developing.

Also, if your darkroom has low humidity, the open tray will cool dramatically due to evaporation, and this will slow any developer down (by reducing the uptake in the first bath, or by slowing the development reaction in the second bath, or both).

You could check both of these issues by developing a single sheet in tray, covering the tray with plastic wrap during development, and agitating by lift-and-tilt. If the numbers go back to normal, do another sheet with less solution (comparable to its share of a multi-sheet batch) and narrow down from there.

If a single sheet in a closed environment still takes double time, then suspect contamination from the tray, hope for a reply from someone with a better idea, or both!

Good luck!

[fireallconsuming]

you should continuously agitate by shuffling from top to bottom throughout the entire cycle, especially if you are attempting more than two or three sheets at a time.

[David Karp]

I use Thornton's formula in trays, but with a slosher. This way, all of the sheets are always in full contact with the developer. I believe that the others are correct. You need to shuffle more.

In the A bath, you need to make sure that the emulsion soaks up the developing agent. If it is in contact with another sheet, this might inhibit this process.

Then, when you move the sheets into the B bath, you must make sure that the emulsion is receiving fresh activator. Again, if the emulsion is in contact with the sheet on top of it, this is probably inhibiting the process. I think this would be the reason that your developing times have increased.

For what it is worth, I always develop for 5 minutes in A, 5 minutes in B. With the slosher, I agitate for the first 30 seconds in each bath, then for ten seconds each minute. If I was using trays and shuffling I would try to shuffle continuously. I prefer the slosher to avoid scratches.