Quote Originally Posted by FilmIs4Ever
Sorry if this has been answered before or if it is something that every competent photographer should know, but what is involved with replenishment? What is the proper way of replenishing solution? Does it depend on how much a particular solution has processed, how old it is, how much solution has evaporated or sloshed out of the tray during processing, or a combination of all or some of the above? Also, once a solution has been replenished, must it then be discarded, or can it be replenished multiple times. When I was taught how to process B&W, I was told to buy HC-110, because it was cheap and replenishing something like D-76 would be a "pain in the ass" along with shifts in consistency from before to after replenishment. Granted this was for film development which I am much more reluctant to replenish for than something as unimportant as a single piece of paper here and there, but is there any truth to the difficulty of determining the proper rate of replenishment?

~Karl Borowski
I don't think there is a single correct answer to this question in B&W or colour.

The obvious answer is to follow the manufacturers recommendation, which will normally state so many ml replenisher for each film or sheet of 10x8 paper. Replenisher itself may be a normal strength working solution or something much weaker, whatever it is will be disclosed in the data sheet from the manufacturer.

I tend to take note of the manufacturer recommendations and then once a solution is supposed to be getting exhausted watch carefully for signs of exhaustion. If I see an indication of exhaustion, I replenish :-)

I also look for missing solution, if I mixed 600ml originally (which would fill a bottle to the top, and now I'm down to 500 ml, I'll mix another 100ml of working strength solution and add it to the old so thatI continue to deprive the solution oxygen when I bottle it.

I do use a propane/butane squirt (cigarette lighter fluid) in every bottle before I close it to remove the oxygen, which helps a lot with longevity of developers.

Some metrics for you. I'm still using patterson RA4 dev originally mixed in November 2004, replenished 3 times to make up volume. The Patterson Bleach-Fix has been replenished once to make up volume. I have not once replenished because the chemistry is showing signs of exhaustion. I use this chemistry at room temperature (~24C)

I use Agfa C41 colour kits typically for 8 x 120 films rather than the 5 x 120 that they state. The kits easily last 4 months from mixing as long as they are stored back in airtight bottles after each roll of film.