Do not subject these old photos to water, no matter what the miracle ingredient is. The whole photography-and-chemical process is alchemy, wizardry, and research; all in one. It worked the first time, don't press your luck. They don't smell like cat urine because cat urine is the cause you speculate on. Only an idiot would plop them in a tray of water now. In another hundred years, someone will say they smell like they were in an old person's house, or they smell like a box of 70's record albums.