Does development time with HC-110 scale with dilution?

When I started developing my film at home, I settled on HC-110 as my developer for HP5+, the film I shoot most often in 35mm. Since I was new to developing film, I chose (unofficial) Dilution H (1:63) since it resulted in relatively long development times which would help lessen the effects of any newbie errors I might make. I did some testing initially that indicated I should use a development time of 10m 30s for HP5+. I've been developing this way for a couple of years now and I get good, consistent results.

In order to shorten development times and make it easier for me to develop several rolls at a time, I'm thinking about moving to the more common Dilution B (1:31). My question is, can I assume that the development time will scale linearly with dilution? i.e. Will I get similar results if I develop using dilution B for half the time that I'm using for Dilution H, or approx. 5m 15s? I see that Ilford's data sheet for HP5+ lists a development time of 5m for HP5+ in HC-110 so that seems consistent with my assumptions.

If that development time for Dilution B makes sense, would it be wise for me to alter my inversion agitation frequency as well? I'm currently agitating continuously for the first 30s and then doing 3-4 inversions every 30s after that. I'm wondering if that will be too frequent with Dilution B and perhaps it would be better to use Ilford's recommendation of 4 inversions during the first 10s of development and then 4 inversions during the first 10s of each subsequent minute. I'm concerned that my current agitation scheme will result in a negative with excessive contrast when used with Dilution B.

I realize I could do another round of testing using Dilution B but I did quite a bit with Dilution H and I'm looking for a bit of a shortcut this time around.

Most of the people who start out with unofficial dilution H start out with the common internet wisdom of using times that are twice the recommended times for official dilution B, so reversing the approach makes sense to me .
Don't change your agitation pattern - if necessary, after trying the new dilution, adjust the time instead.
FWIW I recommend Jason Brunner's unofficial 1 + 49 dilution, which to all intents and purposes is the same as official dilution E (1 + 47). See the info in this Photrio resource: https://www.photrio.com/forum/resources/hc110-made-simple.220/

MattKing said:

Most of the people who start out with unofficial dilution H start out with the common internet wisdom of using times that are twice the recommended times for official dilution B, so reversing the approach makes sense to me .
Don't change your agitation pattern - if necessary, after trying the new dilution, adjust the time instead.
FWIW I recommend Jason Brunner's unofficial 1 + 49 dilution, which to all intents and purposes is the same as official dilution E (1 + 47). See the info in this Photrio resource: https://www.photrio.com/forum/resources/hc110-made-simple.220/

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Thanks Matt.

I'm curious, why do you suggest Jason Brunner's 1+49 dilution instead of Dilution B? One thing I want to ensure is that whichever dilution I use contains enough developer to develop multiple rolls at once. I've been doing one roll at a time using Dilution H because of how dilute the developer is.

One of the reasons I like 1 + 49 is that it means 6 ml of syrup/roll in a 300 ml tank - essentially the capacity recommendation for HC-110 that Kodak indirectly gave.
That scales up nicely with my three (135) roll, 1 litre Paterson tank - with just an extra 2 ml of syrup needed.
Many are comfortable with 5 ml of syrup/roll, so they have no trouble with 10 ml of syrup in a two roll, 500 ml tank.
In addition, the 1 + 49 arithmetic is really easy to work with

MattKing said:

One of the reasons I like 1 + 49 is that it means 6 ml of syrup/roll in a 300 ml tank - essentially the capacity recommendation for HC-110 that Kodak indirectly gave.
That scales up nicely with my three (135) roll, 1 litre Paterson tank - with just an extra 2 ml of syrup needed.
Many are comfortable with 5 ml of syrup/roll, so they have no trouble with 10 ml of syrup in a two roll, 500 ml tank.
In addition, the 1 + 49 arithmetic is really easy to work with

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I'm a bit leery of 5ml/roll in a 500ml tank. That seems like it might be an invitation for under-development. But 1+49 does work out a lot nicer mathematically than 1+31. I suppose if I did 15ml of concentrate and 485ml of water that would be close enough to 1+31 and give me enough developer in the tank for two rolls.

Yes, H is double the time of B. I use both and the main decider of which one gets used is whether the time will be too short (uneven) or too long (boring). It takes so long to run out of a bottle in either case, so the economics don't really matter here.

I believe the linearity of time/dilution will break down at either extreme end of the graph, but not in the middle where B and H both are.

Matt has a good point about 1+49 being easier on the mental math. I might try that sometime.

Regarding inversions, when development time doubles I usually keep the total number and length of inversions the same. In other words invert every 2 minutes instead of every 1 minute. Many developer data sheets also suggest this.

loccdor said:

Yes, H is double the time of B. I use both and the main decider of which one gets used is whether the time will be too short (uneven) or too long (boring). It takes so long to run out of a bottle in either case, so the economics don't really matter here.

I believe the linearity of time/dilution will break down at either extreme end of the graph, but not in the middle where B and H both are.

Matt has a good point about 1+49 being easier on the mental math. I might try that sometime.

Click to expand...

Thanks!