Distilled (AKA "DI"--or DeIonized, though not truly the same) water is of course simply boiled water, cooled through a pipe. From a purely technical standpoint, the relative purity of water is determined by its electrical resistance per unit volume, typically 1cc (or mL). The value of 100% absolutely pure, nothing but hydrogen and oxygen water is 21MΩ/mL. Any conductance value greater than that indicates some level of impurity. However, for comparison:
21MΩ/mL= 100% pure water; virtually impossible to achieve outside of an MIT research lab. No worries.
18.3MΩ/mL= Ultra-pure water used in medical clinics, hospitals, etc. Usually not distilled, but highly filtered, deionized water. So pure in fact you can cause yourself problems if you were to drink a lot of it (it's completely tasteless, FWIW). If you know someone who works at, or live near a dialysis center like DaVita, Fresenius, or The Dialysis Center, you can get gallons of their water for free; they make use about >800 liters a day, and waste more than half flushing lines, or testing. They'd never miss a few gallons at a time.
10.0MΩ/mL= Minimum standard for medical-grade, AKA "Type 1" water purity.
6-10MΩ/mL=Typical steam distilled water at the store. Water will leech out minor crap from the plastic bottles they use, which are themselves somewhat permeable to atmospheric contaminants. That said, this water is completely acceptable to use for all photographic purposes.
0-.5MΩ/mL=Tap/well/bottled drinking water. Very unlikely you have a lower (purer) conductance value from these sources. One may encounter no problems whatsoever, or have to jump through hoops to get good darkroom work done.
Point being, unless you are a healthcare worker with access to the really good stuff, the distilled water at the store is just fine to use.
Depends on who you ask; I've read anything from 30 seconds to 3 minutes! I personally use two 60-second rinses with constant agitation, and am likely overdoing it at that.
So it has been said. Gold toner has also been recommended as the pentultimate archival treatment. Problem with most selenium toners is that they contain ammonium thiosulfate--a fixing agent! Since that compound is alkaline, you can skip the usual 30-minute rinse before toning by using an alkaline fixer like Photographer's Formulary TF-4 with your film. You just give the film a minute or so water rinse to remove the bulk of the fixer, then soak your film in 1+29 dilution of KRST (Kodak Rapid Selenium Toner) for the recommended 4 minutes @ 68°F/20°C, then rinse as normal.
Hope that info is helpful!
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