Here's more of the story on water/vinegar stop baths... Water alone is a good stop bath but it works by diluting the developer, which takes longer than the acid stop bath's chemical reaction. You need more agitation to eliminate streaks.
Those spots than stop baths cause are from gas bubbles lodging on film when the acid level is high. I have had good luck when mixing 1 part distilled white vinegar with 9 parts water... less odor plus no developer carryover into the fixer... the fixer lasts longer and stays cleaner. When you mix developer & fixer directly, ammonia gas is formed and that has its own unpleasant side effect. If you want to add a few drops of bromo thymol blue (BTB) as an indicator it will turn purple when your home made stop bath becomes neutral and no longer works. SPRINT adds vanilla scent to their stop bath but it's too heavy for me... I'm going to try something like a few drops of wintergreen someday. pinhole on! Jim K ----- Original Message ----- From: "Gordon Holtslander" <hol...@duke.usask.ca> To: <pinhole-discussion@p at ???????> Sent: Thursday, December 20, 2001 2:33 PM Subject: Re: [pinhole-discussion] Re: vinegar as stop bath > Develpoers depend on an alkaline environment. When the film developer combination is placed in an acidic environment development slows > down or ceases completely. > > Stop bath is a mild acid, it lowers the pH of the environment to the extent that the developer can no longer function and thus stops > development. Water can also be used to lower the pH, but it does not lower the pH to the same extent as an acid. Water usually has a > neutral pH of 7- though the pH of water varies considerably from location to location. > > Water can usually be used to stop development. The caveats are if you have very alkaline water, or use a developer that works with a > neutral pH (I don't know of a developer that works at a neutral pH) it may not work > > Because water is not as acidic as stop bath it will not neutralize the dveloper as quickly as stop bath. Leaving it in the tray longer > will account for this. > > Stop bath may be necessary when the development process needs to be hatlted immediately. > > Gord > > > > > > Hi everyone, > > > > > > While we're still talking about darkroom chemistry... > > > just wondering if anyone has tried using vinegar as a > > > stop bath in the darkroom. Obviously there would be > > > no colour change when the pH gets too high, but I > > > don't process large volumes of prints at any given > > > time so I can't see this being a problem. > > > > > > > _______________________________________________ > > Pinhole-Discussion mailing list > > Pinhole-Discussion@p at ??????? > > unsubscribe or change your account at > > http://www.???????/discussion/ > > _______________________________________________ > Pinhole-Discussion mailing list > Pinhole-Discussion@p at ??????? > unsubscribe or change your account at > http://www.???????/discussion/ >
