How long does mixed developer last? HC-110 and D-76

Kodak's D-76 sheet (J-78, revised December 2017) gives stock D-76 6 months in a full, tightly closed bottle and 2 months in a half-filled one. Replenisher D-76R has the same figures. Stock D-76 as a working solution keeps 24 hours in a tray and 1 month in a tank with a floating lid. For D-76 at 1:1 the sheet lists a tray life of 24 hours and no stored life, so mix 1:1 just before use.

Kodak adds that partly filled bottles allow some oxidation of the solution.

For stock, both sheets give 6 months in a full bottle against 2 in a half-full one. In HC-110 the more dilute solutions have shorter lives: dilutions B and D keep 3 months in a full bottle, E keeps 2, and F has no storage figure at all.

HC-110 concentrate is thick, so Kodak suggests making a stock solution first: one part concentrate and three parts water. A liter of stock takes 250 mL of concentrate and 750 mL of water (my arithmetic). Dilution B from that stock in a 500 mL tank takes 63 mL of stock, which matches the 63 mL Kodak's table prints. Straight from concentrate the same tank takes 15.6 mL.

My suggestion: keep stock in several small bottles filled to the neck instead of one large one, so every bottle you open is still full. Kodak's figures support that, since a half-full bottle of stock keeps a third as long. Write the mixing date on each bottle.

The tables above are for solutions that have not been used. Developer that has already processed film loses strength with each roll, and the reuse calculator handles that with longer times. Some one-shot developers have much shorter limits: Ilford's Ilfosol 3 sheet says not to keep the working solution longer than 24 hours.

Once the developer has done its rolls, the fixer is the next bottle to count: see how many rolls a liter of fixer handles.