Darkroom Digest: Stop Baths - Water vs. Acid

August 08, 2017  •  9 Comments

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In this article, I thought it might be helpful to compare water versus acid-based stop baths and open up the conversation with other photographers.  

I should first cover the basic function of the stop bath.  It should be obvious, but I will cover it anyway.  The function of an acid stop bath is to stop development as completely and quickly as possible.

There is a relationship between development times and the stop bath that should be briefly mentioned, whether we are discussing film or prints.  In this article, I focus on black and white film development.  The shorter your development time, the more critical the stop bath becomes.  The longer the development time, the less likely it is for the performance of the stop bath to have a visible impact on your intended results. 


There are advantages and disadvantages to acid stop baths that darkroom photographers should be aware of include:

  1. When you are using an alkaline developer and move your film in an acid stop bath, unwanted pH variations are likely to occur.  
  2. If you black and white film developer contain carbonate, an acid-based stop bath can cause unwanted pinholes in some films.  It is important to perform tests with non-cortical films before working on anything serious. 
  3. And the most important concern for me is that acid stop baths can cause swelling of the gelatin in some films which can lead to loss of image quality.  

On the other hand, when you use a water stop bath in place of an acidic stop bath, it can create a different set of circumstances that you should be aware of.  

  1. It should be obvious, but when you place your film in a water stop bath, development does not immediately cease development.  
  2. In fact, the developer becomes very dilute in the water and the first place it exhausts is in your highlights, but it will continue to develop a little longer in your shadows.  This may not be a bad thing, just something to be aware of.  
  3. The biggest benefit of a water stop bath vs. an acid-based stop bath is the sharpness-enhancing adjacency effects that will occur.

If you are interested in the information in this article, you will likely want to read my article: Exploring D-23 Split Bath Large Format B&W Film Development.

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Susan Huber(non-registered)
I use my own well water from my reverse osmosis water pump as a stop. I find that a regular stop would pit my large format film. For a home darkroom like mine, I chose methods of toxicity, ease of obtaining chemicals, simplicity and safety to be paramount.
Bob Dungan(non-registered)
I use Caffenol CM(rs) as a developer on Arista.EDU Ultra film. I use a plain water stop bath. I dump the developer and fill the tank, and, using the stirring rod I agitate for 30 seconds. You see a lot of color from the caffenol in the water when it is poured out. I fill the tank a 2nd time and repeat. You just see a little color in the water. I fill and repeat a 3rd time and there is no color in the water. My fixer lasts longer by washing three times. I have been doing this for some time now with good results.
Pablo Coronel(non-registered)
Developer "quenching" works well in water for 35mm, I use it all the time with 1 shot developers such as Rodinal, DDX or D76 1+1.

However very active developers will require a diluted acid stop bath.
Citric acid at 1% is a good smelling alternative.

Water bath development technique is a very old method to handle high contrast situation, it is mentioned in a Gevaert Manual (1917)
For reference, Joe Lipka published a good article in the early 00s which made me try D23 again,

However I decided to go the Vitamin C route, after long discussions with Patrick Gainer about the beauty of this developers. And yes, Water bath development works on these but to a much lesser extent than D23
Joe Baldwin(non-registered)
My experiences is that if you use a water stop during the process of determing your EI and development time, then all variables are in the process and water has no effect. I might mention that i would never use tap water for any part of the development process, including the wash and mixing of developer and fix. Tap water is loaded with an unbelievable number of chemicals that will react with developers. I learned this the hard way. I only use distilled water in all processes of film development. Your tap water may be fine now but you never know when your local government is going to be required to add some chemical to the process and they will not notify you.
Marcus Schluschen(non-registered)
I use a double water stop bath. The first gets dumped after only 15 - 20 seconds, to remove the bulk of the developer.
No comments posted.

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