Streaks In Sky

[alexkj]

Hi!

I've been experiencing some streaking in the sky of prints. It is the last batch of Kodak Endura made so my assumption is it has to do with being expired, but I am confused why it is only in images with sky and not in the highlights in general.
Here is some info:
- Has a stop bath so I'm guessing it's not developer runoff
- Only happens in sky, not even highlights
- Doesn't happen with other papers
- Uploaded photos from the same batch of paper/film/day in the darkroom,etc for reference

Thanks for any help!

 

[koraks]

so my assumption is it has to do with being expired

This is not the case. Expired paper does not streak etc. It generally just shows fog that's proportional to the degree it's expired.

The problem seems to be uneven wetting, insufficient agitation or a problem with carryover into too weak a stop bath and ultimately blix. The reason why it shows up mostly on skies is probably that the cyan layer is more affected. The cyan layer is the top layer of the emulsion stack on color paper, so perhaps that's why it's the one that responds the strongest to things like uneven wetting etc. The other reason why you don't see much of the problem elsewhere in the print is that the somewhat subtle streaking is overpowered by the image-wise contrast. It's there alright, just not very visibly so.

How are you developing? Tubes, trays, RT? What development time & temperature? What stop bath do you use? Please describe your process in detail.

 

[alexkj]

This is not the case. Expired paper does not streak etc. It generally just shows fog that's proportional to the degree it's expired.

The problem seems to be uneven wetting, insufficient agitation or a problem with carryover into too weak a stop bath and ultimately blix. The reason why it shows up mostly on skies is probably that the cyan layer is more affected. The cyan layer is the top layer of the emulsion stack on color paper, so perhaps that's why it's the one that responds the strongest to things like uneven wetting etc. The other reason why you don't see much of the problem elsewhere in the print is that the somewhat subtle streaking is overpowered by the image-wise contrast. It's there alright, just not very visibly so.

How are you developing? Tubes, trays, RT? What development time & temperature? What stop bath do you use? Please describe your process in detail.

That was my inkling too but since it doesn't happen with other paper I felt like it could maybe be ruled out. It's through a converted RCP 20, Fuji RA Pro Chemicals, Indicator Stop Bath ( thought about changing this to acetic acid at a stronger ratio and see if that helped, but seems like the stop is just acetic acid with the added indicator so a less diluted stop would do the same thing, which I tried). Chemicals stay at 95 F.

What's throwing me off is if it does not occur with Fuji crystal archive, DPII, or even a batch of very very expired kodak paper. Normally I can get to the bottom of an issue but this one is really stumping me.

Thanks for your help

 

[koraks]

What dilution are you using the stop bath at?

Other things to look for are proper mixing ratios of the developer and blix (especially the former) so you know you're actually getting complete development. I wonder if that's the case. Also make sure that the pickup roller of the RCP20 remains dry, although the pattern of that issue is different from the streaking you're getting.

What's throwing me off is if it does not occur with Fuji crystal archive, DPII, or even a batch of very very expired kodak paper.

That is odd indeed. I can see how you might run into a problem with Endura and not plain Crystal Archive, but then you'd likely also see problems with DPII. The reason is the thicker emulsion on DPII, Endura and also Maxima, which make them a little more prone to insufficient development - although uneven development issues would usually affect all papers.

The very, very expired Kodak paper that gives no streaking, is that also Endura, or something like Royal?

this one is really stumping me.

Yeah, this is a tricky one for sure!

 

[alexkj]

What dilution are you using the stop bath at?

Other things to look for are proper mixing ratios of the developer and blix (especially the former) so you know you're actually getting complete development. I wonder if that's the case. Also make sure that the pickup roller of the RCP20 remains dry, although the pattern of that issue is different from the streaking you're getting.



That is odd indeed. I can see how you might run into a problem with Endura and not plain Crystal Archive, but then you'd likely also see problems with DPII. The reason is the thicker emulsion on DPII, Endura and also Maxima, which make them a little more prone to insufficient development - although uneven development issues would usually affect all papers.

The very, very expired Kodak paper that gives no streaking, is that also Endura, or something like Royal?



Yeah, this is a tricky one for sure!

Good news! Your questions made me think hard about what could be happening. I generally have to keep the stop filled to the brim when using higher emulsion papers or their will be spots. I wondered if maybe it got bumped here and there and teeny bits of stop made their way into my developer working tank solution. I made a new working solution and problem solved!

I am wondering if you have any advice on a way to not fill the stop bath so full so this doesn't happen again. With crystal archive I can use the 500ml as is intended for the RCP, but the higher emulsion papers I've had to fill it to the very top.

I appreciate your advice - always nice to talk it out with someone that understand the process!

 

[koraks]

Oh, that makes perfect sense; so the streaking we're seeing is basically just stop bath sloshing over the edge of the middle slot! Great that you seem to have found the culprit.

I am wondering if you have any advice on a way to not fill the stop bath so full so this doesn't happen again.

That's the tricky bit, I guess. The RCP20 is a bit problematic in that it has the sponge roller as a stop bath applicator, which means that the process is inherently prone to unevenness/mottling. What I find helps considerably is to mix a reasonably concentrated stop bath. I use cleaning vinegar 1+4, which boils down to ca. 2% acetic acid concentration, and this may need to be replaced after a few dozen prints (YMMV and all that). What I've not tried, but might work is to use a more aggressive mineral acid, like sulfuric acid, at a 1% concentration. This is similar to an ECN2 process and might be the ticket here as well. Give it a try - but be careful handling concentrated acids (this is true for acetic acid just the same btw).