Clear/white "blotches" visible in skies / RA4 process

[ste976]

No, RA4 is a develop to completion process for the most part. The difference in exposure will be marginal or even zero for a longer development time - especially if you also reduce processing temperature.
You can go below 32C just fine, too.



Sounds like it's time to fix some more problems; a 3-4 second exposure time should be consistent enough not to produce visible variations even with a halogen/tungsten bulb and a basic timer. What kind of density variations are you getting? Can you post some examples?

With lens at f11 an 8x10 print from 6x7 negative (without neutral density filtration, just Y and C) needed 3 or 4 seconds. But sometimes I got small variation in density in print from test print to final print. I thougth that longer exposure times would solve problem if due to tiny fluctuation in light source. My enlarger (durst modular 70) has a density filter (max 2 stops) so i used that to extend exposure time to around 10 seconds. Density print now seems consistent.
Where should a look to have consistency also at 3/4 seconds. I would prefer to work at 3/4 seconds. That would be faster.

Light bulb is new. I can try to check the contacts

 

[koraks]

What kind of timer do you use?

I have a feeling your density variations aren't related to the exposure time and that they just coincided with your print development process that's not in control yet.

I suggested it before, but I really recommend giving tray development a try, at least for one session. If you have space to exposure a print, you also have space to set up 3 small trays for small test prints. Work at room temperature so you don't have to worry about temperature fluctuations (small fluctuations don't matter anyway, especially at low temperature and long processing times).

Make a few identical test strips and develop them at room temperature for 90 seconds, 120 seconds, 150 seconds, 180 seconds. Ensure that the exposure is such that you have a black patch on each strip. If not, do it again and adjust exposure so that you have black somewhere. Place the strips that are developed at different times next to each other. The first strip that shows a black that's pure black and not blue, is approximately your minimum development time for room temperature. You'll notice that the strips processed at a longer time show very little difference; they may have slightly higher density or contrast, but the difference is slight.

Use the minimum development time to process a couple of test prints. See if the consistency problems go away. Once you get consistent results (across let's say 5 prints or so, at least) with your 10-11 second exposures, do the same with 3-4 second exposures. At this point you'll be better able to determine where the problem in your process is.

Sometimes it takes some effort dialing in your process; once you've got this down, it's pretty easy/straightforward.

 

[ste976]

What kind of timer do you use?

I have a feeling your density variations aren't related to the exposure time and that they just coincided with your print development process that's not in control yet.

I suggested it before, but I really recommend giving tray development a try, at least for one session. If you have space to exposure a print, you also have space to set up 3 small trays for small test prints. Work at room temperature so you don't have to worry about temperature fluctuations (small fluctuations don't matter anyway, especially at low temperature and long processing times).

Make a few identical test strips and develop them at room temperature for 90 seconds, 120 seconds, 150 seconds, 180 seconds. Ensure that the exposure is such that you have a black patch on each strip. If not, do it again and adjust exposure so that you have black somewhere. Place the strips that are developed at different times next to each other. The first strip that shows a black that's pure black and not blue, is approximately your minimum development time for room temperature. You'll notice that the strips processed at a longer time show very little difference; they may have slightly higher density or contrast, but the difference is slight.

Use the minimum development time to process a couple of test prints. See if the consistency problems go away. Once you get consistent results (across let's say 5 prints or so, at least) with your 10-11 second exposures, do the same with 3-4 second exposures. At this point you'll be better able to determine where the problem in your process is.

Sometimes it takes some effort dialing in your process; once you've got this down, it's pretty easy/straightforward.

i use a colorstar 3000 as a timer.
the chemicals are in a water bath with a heater at 32C.

not so sure about using room temp. here in milan room temp changes over the year (and actually over this very month) from 16-17 C till up and above 30C. it would not be very consistent. but i can do the test you suggest with different dev times also with the "drum setting/chemical in water bath at 32C" to find minimum dev time.

the print density variation i had when working at 3-4 seconds exposure time were about 1/3 or 1/4 of a stop. could it be some fluctuation in light intensity? i can actually see tiny fluctuation in the light of the enlarger.

 

[koraks]

i can actually see tiny fluctuation in the light of the enlarger.

Ah. A visible fluctuation in light output is totally unacceptable for color work. See if you can clean the contacts in the bulb socket, or replace the socket altogether.

not so sure about using room temp.

Yea, most of the time when I suggest people try tray development at room temperature they don't do it because they don't think it'll work, it'll be difficult, temperatures will fluctuate etc. Let me put it this way - the suggestion is on the table. I put it there for a good reason. Whether you try it, is up to you. My business is not to try and bring the gospel to people; I give suggestions on what I know can help in troubleshooting.

 

[ste976]

Ah. A visible fluctuation in light output is totally unacceptable for color work. See if you can clean the contacts in the bulb socket, or replace the socket altogether.



Yea, most of the time when I suggest people try tray development at room temperature they don't do it because they don't think it'll work, it'll be difficult, temperatures will fluctuate etc. Let me put it this way - the suggestion is on the table. I put it there for a good reason. Whether you try it, is up to you. My business is not to try and bring the gospel to people; I give suggestions on what I know can help in troubleshooting.

all right, yes i'll have to check the contacts of the light bulb. i would prefer to work with 3-4 seconds exposure time rather than 10

as with tray processing, you're right i am bit biased because when i tried it (a few years ago) it was a bit of nightmare for me. i end up sticking my fingers into the chemicals because i could not manage to take the paper out with tongs, chemicals went all over the place and i my hands were itchy for a bit while...
anyway i'll give it a try when i set up a new darkroom, at the moment the enlarger is an a sort of closet (nice thing is that it has no windows to blank out) which barely fits me and the enlarger

btw the bloches problem is gone, develop time was the problem. i'll do a test soon to find out optimal minimum develop time using the method you suggested!

 

[koraks]

Wear nitrile gloves.

btw the bloches problem is gone, develop time was the problem.

Yeah, I thought so, but the flickering enlarger bulb is a liability. See if you can get that fixed.