Kodak TMX in HC-110 Dilution B, approx. 40% depleted
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  2016 April 2    Film   Developing

Introduction


Kodak HC-110 is a superb developer for black & white film.  The concentrate has a long shelf life, it works at high dilutions, and it's very good for push processing.  Sure, I've used D76 and it's great, but there's nothing quite like HC-110.

Some people say you should mix HC-110 as a "one-shot" developer.  That's sort of the traditional method.  I wanted to know if it was feasible to mix diluted HC-110 in a larger batch and keep re-using it for a while.

Let's see if that works, and how.


A Quick Note

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In This Article


Dilution B

How Much Per Roll?

A Larger Batch

Adjusting the Dev Times

Special Notes For 4x5 Film

Possible Source of Error

Blank Negatives!

Results So Far

Buffering etc.

Conclusion




Dilution B


Kodak uses letter-codes for the various dilutions of HC-110.  The dilution factors are not the usual 1/10th, 1/100th, or that sort of thing.  Instead they have denominators like 16, 20, 32, 40, 48, and 120. 

For example, Dilution E is 1 volume of HC-110 concentrate plus 47 volumes of water.  That's a dilution factor of 1/48, for a total of 48 volumes of solution.

Dilution A.......1+15
Dilution B.......1+31
Dilution C........1+19
Dilution D........1+39
Dilution E........1+47
Dilution F........1+79
Dilution G........1+119
Dilution H........1+63 
(Not an official Kodak dilution; see this page.

These don't follow a neat trend (as you can see), but they become familiar after a while.  Dilution B is probably the most popular one.  You could make other dilutions of HC-110, such as 1+99 (i.e., 1:100), obviously, but you might have to work out your own dev times.


Kodak HC-110 concentrate, shown here in a glass bottle.  It doesn't ship like that; you have to get your own glass bottle.





How Much Per Roll?


It takes about six milliliters of HC-110 concentrate to develop a roll of 120 film or one roll of 135-36.

No matter which dilution you use, that 6 ml has to be there.

In the Paterson tank, I use 350 ml for one roll of 35mm.  (Offhand I think the minimum is 290 or 300 ml).  350ml of Dilution B will contain about 11 milliliters of HC-110 concentrate.  That's more than enough to do a roll of 35mm.

In fact, it's almost enough to develop two rolls of 35mm.  (350ml can't fit two reels in it at once; you'll have to re-use the solution.) 

If you want to do one roll of 120, the Paterson Super System 4 tank requires about 500 ml of liquid to cover the reel.  That's going to contain (500/32) = about 16 ml of HC-110 concentrate.  Again, that's got more than enough for one roll, easily enough for two, and almost enough for three rolls.  To be able to do that, you'll have to re-use the liquid; 500ml can't fit two or three reels in it at once.  One at a time, with some percentage depletion at each step.

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A Larger Batch


Often I'll just mix up 350 ml of Dilution B for one roll.  However, that leads to a lot more measuring if you want to keep developing more rolls of film. 

You could mix up one liter of Dilution B, then use whatever amount is needed for one roll (300 or 500 or whatever).  Then at the end, you could pour that back into the 1-liter working solution.

The result is a solution that's not really "Dilution B" any longer.  It's been depleted by whatever amount was necessary to develop that roll of film.

When you measure out the next batch, adjust the develop time accordingly.  Now, let's see how to do that.

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Adjusting the Dev Times


A liter of Dilution B requires 31 ml of HC-110 concentrate, plus enough water to make up 1000 ml of solution.  That liter should be able to develop five rolls of 120 film or 135-36. 

You develop one roll, then return that 500 ml of solution back to the one-liter bottle of Dilution B.  You do this because that 500 ml still has enough developing power for at least one, maybe two rolls of film.

So now we assume that your 1 liter has used up 6 of the 31 ml of concentrate.  That leaves 25 ml.  Thus your developer is now at about 80% strength. 

On the second roll, developing time should now be 1/0.8, or 1.25 times as long.  So, if the first roll was 5 minutes, the second roll would be 6.25 minutes.  Or, if it was originally 14 minutes, it would now be 17.5 minutes.  At this stage you can still get usable negatives even if you don't use the conversion factor, but you'll probably notice a difference. 

On the third roll, the developer would be at 60% strength.  Develop time would be 1/0.6, or about 1.67 times normal.  A 5-minute develop would now require 8.3 minutes.  If our roll of TMax 100 would have been 6 minutes in Dilution B, it's going to need a full ten minutes now. 

This is where you'll really start to see a difference if you don't use the conversion factor.

By the fourth roll, the solution is at 40% strength.  Develop time would be 2.5 times normal.  To make sure you had 6 ml of concentrate for the roll of film, you'd now have to use 500 ml of the solution.

By the fifth roll, the developer has only about 6 ml of active concentrate left.  That 6 ml is contained in a total volume of 1 liter.  The Universal 2-reel tank won't even hold a liter;  you'd need the Paterson 3-reel tank.  (That's also good for 4x5 developing.) 

The effective concentration by this point is only about 20% of the original.  Thus, by the fifth roll of film, developing time should be 1/0.2, or five times longer than normal.  A roll of Tri-X that would have taken 6 minutes would now require 30 minutes.




Special Notes for 4x5


A sheet of 4x5 has roughly one-fourth the area of a roll of 120 or 135-36.  Some people develop single 4x5 sheets in the Paterson tank, leaving out the reel but keeping the center column in place (because it keeps the light out.)

Figure on a sheet of 4x5 using up about 1.5 ml of HC-110 concentrate.

You can calculate the percentage remaining at any time, knowing how much gets used up by each film.  Let's say you developed one roll of 120 and a roll of 135-36 from that liter of Dilution B.  After those two rolls, your solution has about (30-12)/30 of the total capacity, or 60%.  (Remember to return the partly-spent solution back to the one-liter container.) 

So, the time factor for the next film would be 1/0.6, or 1.67.

When you develop something in the solution that has 60% of the Dilution B strength, you'd run the develop time for 1.67 times normal.  A six-minute dev time would now be ten minutes.  So, that one sheet of 4x5 would develop for 10 minutes.

Now, when the sheet is done developing, you've used up another 1.5 ml of concentrate from the total amount in your liter.  Therefore, in our example, that would leave the solution at (30-13.5)/30, or 55% of the total capacity.

One roll of 120, a roll of 135-36, and a sheet of 4x5 leaves your liter of Dilution B at 55% capacity.  That means whatever you develop next in it should have a time factor of 1/0.55, or 1.82.  So if you were going to develop something that calls for 6 minutes, the time would now be 10.9 minutes.  That's ten minutes, fifty-four seconds, and obviously you could just round that up to eleven minutes.

If you didn't develop anything yet in the solution, then of course your first 4x5 negative would develop at the normal time.  Whether it's Tri-X or HP5 Plus, six minutes in Dilution B is good.



Possible Source of Error


I'm not sure yet if the 6 ml figure is for an "average" roll of film, or whether it's a maximum amount.  It doesn't matter so much for 35mm, because a variety of pictures will average out across a whole roll, which is treated as one piece of film as far as the developer is concerned. 

Where you might start to see errors in these methods is if you develop a lot of sheet film. 

Sheets of bright white subjects (dense, dark negatives) use up more developer.  Very thin negatives with big, clear areas are not going to use much developer. 

So far, the figure of 6 ml for a roll of film and 1.5 ml for a 4x5 sheet is producing great results.  I don't know how many darkroom enthusiasts bother with this level of precision, but if you're serious about film photography, this is the way to go.  You will see that if you don't use a correction factor, your third, fourth, and fifth rolls will be toast (getting worse in that order).

The next section details other possible sources of error, this time mostly chemical rather than photographic.

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Blank Negatives!


Blank negatives (no development) can happen with any highly-diluted developer.  Some ways to avoid this:

First, remember that film developers tend to be reducing agents.  (In fact they have to be, because they must be able to reduce Ag+ to Ag.)  These can react with dissolved oxygen.  More dilution means the oxygen will ruin them faster.  Cold increases oxygen solubility, but it's probably more than offset by the reduced reaction rate.  I would recommend a separate mini refrigerator for film chems, then figure out how to install a lock on it.  this one should work on any refrigerator.

Second, make sure there's enough total liquid to contain 6 ml of concentrate per roll.  After a couple rolls, you could need 500 or 1,000 milliliters of solution for one roll of 120 or 35mm.  That means if you try to do a roll of film with the usual 300 ml, it could be ruined. 

Third... look at your HC-110 concentrate.  Make sure it isn't dark reddish or brown.  Many people have said HC-110 works fine even when it's browned.  If you want to eliminate this variable for sure, get a fresh bottle of HC-110.  I would re-package it in glass bottles so the air can't oxidize it.  Do that, and it will last for years.  (Store it in a safe place out of reach of the tots, your mother-in-law, etc.)

Fourth... if you use distilled water, make sure to boil it and let it cool.  Distilled water is unbuffered.  Some tap water also has very low buffering capacity.  CO2 from the atmosphere will dissolve in water, produce carbonic acid, and act like a built-in stop bath.  De-gassed water can re-acquire carbon dioxide when it sits for a while.  This will gradually ruin the developer.

Another idea: if the dev solution has been sitting for a while, check it with a pH meter before you try to develop anything in it.  Pouring the solution back and forth from tank to bottle will introduce CO2 (and oxygen).  Eventually there will be enough CO2 that it ruins the developer.  Even a slight shift toward acidity can ruin a dev solution.

Pay attention to the storage life.  As far as auto-depletion goes, Dilution B is supposed to last for at least a month (Kodak Publication J-24).  That's if it hasn't been used yet.  Even mostly depleted, it still ought to last for at least several days to a week. 

Whatever you do, don't try to re-use a partially-spent dev solution for something critical, like someone's wedding photos.  Use it for fun stuff that you can easily re-do if you have to.

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Results So Far


So far I've had very good results by using the methods outlined in this article.  I haven't tried developing that fifth roll (20% strength, whole liter of solution required), but I'll let you know how that goes.  (Get the Paterson 3-reel tank if you're going to do that.)  Remember, once again, that at 20% strength the developing should be about five times longer. The exact time may vary, but that's a good starting point.


Kodak TMX in HC-110 Dilution B, approx. 40% depleted


By the way, these photos were probably 1/2 to 1 EV underexposed.  That's because I didn't bother to correct for the dark orange filter.  The light meter thinks there's more light than the camera is actually getting through the filter.  (These required more post-scan adjustment, but it's OK.) 

My calculations for the dev time seemed to work as hoped.  I have a bunch more film that was developed using the methods on this page;  just have to scan and post it.  (I have a recent roll of Delta 400 at EI 1600 that was the "second roll" in a liter, so the dev time was 1.25 times normal.)

Tmax 100 in very dilute HC-110 is a bit low-contrast to begin with, but I find that it scans well.  You can probably increase the contrast with more agitation;  I let the negatives just kind of sit there, with minimal agitation for the ten minutes. 


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Buffering, etc.


I don't know at what point HC-110 becomes so dilute that it would need extra buffering, but maybe I'd start with carbonate/bicarbonate to give some extra capacity.  Haven't tried that yet, so I don't know what amounts would work best (if any). 

Keep in mind that multi-component solutions don't always act the way you expect when you add buffering agents.  There might be something I didn't think of, too.  Offhand I'd guess they would increase contrast, but then again if you adjust the pH correctly, maybe not. 

One reason I like dilute HC-110 is that it's great for pushing film, because it gives some chance of preserving highlight and shadow detail.  To keep the negatives from getting too contrasty, we use diluted HC-110 and long develop times. 

You should be able to use up the liter of Dilution B within a few days, well within the range of not needing to mess with the chemistry or extend the shelf life.  Just wait until you have five rolls to develop, and you're all set.  Or, if you want to do just one roll or something, mix up some Dilution G or H and use them immediately.  (Dilution G doesn't keep.)

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Conclusion


Can you re-use Kodak HC-110 developer solutions?  The answer is yes, if you do it right.  The results are pretty good from what I've seen so far.  Using partially-depleted developer is very much like using dilute developer, as long as you know how much active developer is in solution.  And as we've seen, you can calculate that amount.  Just don't forget that O2 and CO2 will gradually deplete the solution.

Hopefully this article will help you avoid "blank negatives".  Maybe not in every possible instance, but at least in some of them. 

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