25 grams of citric acid per liter plus 10 g of sodium citrate makes a stop-bath strong enough for 70 rolls of film. Instead of measuring grams and dealing with the citrate I usually dissolve 3 tbsp of acid and add something about a ⅔ tbsp of baking soda. The last batch of this stop-bath was made 7 months ago and still has enough acidity after 58 rolls.

Hiya John - hope you're keeping well.  I never use an actual stop bath.  For film I just use three changes of water.  For paper I use the fixer from my previous printing session followed by freshy mixed fixer.  Most printing is done on RC paper but I treat the odd FB sheets exactly the same.  I'm not interested in archival processing - I'm 70+ years old and don't care what happens to my prints after I kick the bucket (of fixer) LOL.  Best wishes from The Rhondda

I'm another advocate of just using plain tap water for my film stop bath (I don't print my negs). Some of the reasoning was mentioned by a previous commenter. My understanding is the developer in the emulsion is effectively depleted in the highlights so development there stops almost instantly when the water is added. The developer in the shadow areas is not depleted in the shadows, so development there continues for a bit longer, bringing up some additional shadow detail. I've read that in this case shadow development lasts no longer than 30 seconds and typically lasts much less than this. I keep my chemistry alkaline or neutral from start to finish, but I understand every does what works for them. D-23, water stop, two bath TF-2 is my standard. Keeping things simple. Cheers

IMO, the argument between use of stop bath or a water bath comes down to timing. If your development time is 10+ minutes, there isn't a practical difference as to effect on development. However, if your time is 5 minutes, stop bath stops development immediately, whereas a water bath just dilutes but does not terminate the action of the developer remaining in the emulsion, leading to some degree of overdevelopment. The advantage of an indicator stop bath is the inclusion of a pH sensitive dye, which changes color when the pH of reused stop bath increases to a point where the bath becomes ineffective. I'm not sure that the cost of household vinegar plus packs of pH test strips to check its condition before each use works out as significantly cheaper than a retail indicator stop bath. Further, in practice, a water bath is commonly used to just flush developer off the surface of the emulsion (film or paper), relying on the acid fixer to do the chemical work of a stop bath, causing the fixer to degrade more rapidly than with use of an acid stop bath.  Historically (in my misspent photographic youth), the argument for a water bath in lieu of an acid stop bath was that, depending on the composition of the developer, the strength of the stop bath, and the thickness of the unhardened film  emulsion, the acid stop bath and developer could react, producing gas bubbles which would burst through the emulsion, leaving pinholes.  That issue ended when film makers started pre-hardening film emulsions in the 1960s, but the use of water bath carried on. Then, of course, there is the modern issue of using acid stop bath or fixer with pyro development, a topic for aother video.

For film I've taked to mixing up 1% acitic acid stop and using it oneshot. Cleaning vinegar is avaiable in 32% strength locally and is very cheap, and since I already use it for cleaning it's always on hand.

Thanks, John.  It's interesting how many of the chemicals we use can be found at the grocery, hardware store, or swimming pool supplier.  After all, when photography started, there weren't photographic stores.  

Your IR photo at the end of this video is beautiful!

Great idea. and so simple! Thanks. (I use citric acid anyway to get rid of lime, as it won't cause corrosion on metals like vinegar might).

Hey... Can you develop Kentmere Pan 200 with Rodinol and tell us what the dev time should be?

Bad working practice to add water to acid, John. I know that 5% acetic acid is not very "dangerous" but it is still not best practice, ALWAYS add acid to water not the other way around. BTW I use malt vinegar on my fish and chips not distilled white vinegar. In the USA we can buy white vinegar most cheaply during canning season so that's when I stock up.

Thanks for sharing your tips John what l find strange is that l use the same vinegar as you but use only 50ml which gives me a PH of 3 lol...

How long do you need to keep the film in the vinegar stop bath? Thanks.

Good tip with the citric acid. I hate the smell of vinegar in the darkroom. How much is the stain from pyro developers affected?

It looked like you added the citric acid to the vinegar solution? Is this the recipe, or is the idea to use water for the citric acid stop bath?

Also, yes — malt vinegar, not white vinegar on fish and chips. 🙌

Hi John, would you use citric acid stop bath developing film with two bath developer, such as Barry Thornton two bath or as you wrote in your book just stick with three or four changes of water before fixing. I have only used water to stop development since going over to two bath method and seem to produce nice negatives, infact very nice negatives, i now realise that for years and years I've been slightly over developing my films using normal one shot developer such as DD-X.