what happens with c41 if the bleach bath is too short?

[rainer_viertlb_ck]

my atl1000 machine doesnt allow individual programming of the times of

processing. its bleach bath time is 6 minutes, tetanal c41 chemicals

want a time of 8 minutes bleach bath time. the films look good with 6

minutes too,- but i am not sure about this. what happens in the bleach

bath.....

thanks and regards from germany

[dan_sapper]

Bleach step converts the metallic silver (after developer) back to silver halide. Bleaching is done in preparation for the Fix step, which removes the silver halide from the negative. A processed color C-41 image should have no silver metal nor silver halide in it. The final image is made entirely of color dyes. If the bleach step is incomplete, the result is "dirty" looking images. The effect could be described as gritty, sandy, grainy, off-color (yellow-brown).

 

Some film emulsions bleach more easily than others. Generally, high-speed films need more bleach time than slower films. This is just a guideline, not absolute.

[steve_levine]

Silver retention occurs,causes what appears to be excessive grain.

[Bill C]

rainer, I concur with the previous comments, and Dan has described things very well. I'll add a little more.

 

The traditional way for a larger lab to check for this "retained silver" would be to examine film via an "infrared scope"; the color dyes are transparent to IR, so if they see anything at all, it must be retained silver. The specific scopes are pretty expensive; you probably don't want to buy one.

 

There is a pretty foolproof method you can do yourself, but you need to sacrifice a neg. First, pick out one which is most likely to show the problem; this would be a neg with the most dense areas (more silver takes longer to bleach). Cut this neg in half, making the cut cross through the dense area. Rebleach one half for roughly the normal time, then refix, rewash and dry. Now, set it next to the original half on a light table or such. If there is a problem of any significance, you will be able to see it visually (use a magnifier).

[rainer_viertlb_ck]

thanks for your help,

bill,- does this mean that i can put the negs after having had them in the fixing solution one time again in the bleachbath?

[Bill C]

>> ..does this mean that i can put the negs after having had them in the fixing solution one time again in the bleachbath? <<

 

Yes, this should be safe. Probably you should make sure the film has been rinsed in water before going back to bleach. Once you rebleach, finish the rest of the process (ie, fixer, wash, stabilizer).

 

I am not suggesting you do this with all of your film; only a test frame here and there to verify that bleaching is adequate.

[400bpm]

Bleach bypass is often used in cinema to achieve a look something like Saving Private Ryan (though technically that's ENR). They call it "bleach bypass" but it's not normal to bypass the bleach completely. Usually done with a diluted bleach or shortened bleach time. I tried it once with a snapshot roll of film and the result was increased grain and muted colors. It kinda looked like old faded photos from the 70s.<p>

 

there's a few in <a href="http://majestic.coe.uga.edu/photos/">this directory</a> if you're curious.