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?