D-76 to HC-100 - Anyone regret making the change?

Cholentpot said:

Can you give me the recipe you use? Google brings up lots of arguing about everything under the sun.

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Here it is, for 1000ml:

Borax	1.4
Sodium sulfite	60
Ascorbic acid	11.5
Sodium carbonate (decahydrate)	13
Phenidone	0.15

Mixing instructions:
Start with 100ml warm water, say 40-50C. Dissolve the borax.
Add cold water (straight from the tap is fine), let's say 700ml to make 800ml. Dissolve the other ingredients in the order listed.
Make volume up to 1000ml using cold/tap water.

I find the pH ends up a little low (usually around 8.0), so I adjust it by dripping some 10% NaOH into it until it hits 8.20 at 20C.
You could also add some more sodium carbonate to get the pH right.

You can then dilute further if so desired to get your working strength, e.g. 1+1 or 1+2. I mostly use this as a stock (1+0) or 1+1.

The pH won't be perfectly stable over a longer time as the buffering capacity is somewhat limited. I'm not particularly bothered by this as I generally keep it around for only one or two weeks and then mix fresh.

When storing stock or working solutions, keep them in glass bottles filled to the brim and tightly capped so there's minimal contact with oxygen.
Any iron in the water can be very detrimental as has been demonstrated with ascorbate developers, so you may want to use a chelating agent (a very small amount of EDTA or PDTA for instance; something like 0.5g/liter should do, but I haven't tried) or mix the developer with demi- or distilled water. However, I don't bother since I don't keep it around long anyway and prefer to work with entirely or fairly fresh developer for good consistency.

The phenidone I keep as a 1% w/v solution in propylene glycol, which makes it easier to measure. The 1% stock should keep well very long (many months). A 1% solution is easy to measure as 0.15g of phenidone would simply be 15ml of 1% phenidone stock, etc. Since I mostly mix something like 150ml or 250ml developer at a time, this is for me the most convenient way of working.

Note that I listed sodium carbonate decahydrate, but most formulas list the monohydrate or sometimes the anhydrous form. If you use monohydrate, multiply the amount listed by 0.43. If you use anhydrous, multiply by 0.37.

@DREW WILEY, @BradS : point taken. I had read statement(s) that the "settling" was linked to pH changes; if not, I have no conflicting evidence; I have, and will continue to, wait 24hrs between mixing and first use. Next in line for me: establish the equivalence (or time factor, if any) between packaged D-76 and DIY D-76d.
Comforting statement from Anon Ymous

Anon Ymous said:

....
Finally, this pH instability thing is IMHO a bit blown out of proportion. BW work isn't THAT critical and is tolerant of process variations. I was given borax instead of boric acid in the past and mixed D76d with 16g/l borax! The negatives were a bit overdeveloped, slightly coarser grained, but still perfectly usable. Not ideal, but not the end of the world.

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Borax is a buffer. It keeps the pH constant or tries to. After the initial, small quantity, adding more borax to the solution would not significantly increase nor decrease the pH of the solution. It would only increase buffer capacity.

The settling time is not really about pH it is to allow the chemistry to reach a sort of equilibrium state. The pH doesn't noticeably change during this time but the activity of the solution definitely does. You do not need a densitometer to see the difference either. You can see it with your naked eye. Try it.

BradS said:

Borax is a buffer. It keeps the pH constant or tries to. After the initial, small quantity, adding more borax to the solution would not significantly increase nor decrease the pH of the solution. It would only increase buffer capacity.

The settling time is not really about pH it is to allow the chemistry to reach a sort of equilibrium state. The pH doesn't noticeably change during this time but the activity of the solution definitely does. You do not need a densitometer to see the difference either. You can see it with your naked eye. Try it.

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When I mixed D76d with what I thought was boric acid, but was actually borax, the pH of the developer turned out to be 9,2 instead of 8,5, or 8,7 according to Ilford. It's not a bit off, but way off. In this case, adding too much of borax didn't just increase buffering capacity, but altered the pH to the level that a typical borax solution would have.

Altering developer pH will alter it's characteristics. In this case, it became more potent. For the record, I've never used freshly mixed D76, but always wait a day or two before use. I don't know how obvious the state change is, never noticed anything strange by eyeballing negatives developed in reasonably fresh D76/ID11/homebrewed stuff.

Even minor unpredictability in dev activity can be a nightmare if you happen to need exact mask densities or precisely matched color separation negatives. A single change in any variable like the reformulations of HC110 can amount to a LOT of work recalibrating everything. Believe me, if you just spent a week of work and a ten sheets of 8x10 film, and something is off, you might discover all kinds of things about film or developer you didn't notice before!