Ah yes, the wonder, beauty and necessity of clean, pure water! The above shot was taken in the Cayman Islands back in 2011. Such crystal clear water makes it a wonderful place to kick back and enjoy. But clean water is not something easy to find. Living internationally we have often been forced to use bottled water as the liquid that comes from the tap is anything but water!
When I began developing my own film I started to read about the use of distilled water for all chemical mixing and the cleaning of film. I was living in Perth Australia at the time which enjoys some excellent tap water if a bit on the hard side. As I moved to London, I noticed slight changes in my chemical mixes but nothing to worry about. Now I find myself in Jakarta and I am having a host of issues with finding clean, pure and consistent water.
I decided it was time to do a bit of a deep dive into the simplest of items, water and why it is so critical in the development process. Most of what I read was online from a variety of sources but one of my main sources is the "Sciencing" website.
Why would we want to use distilled water?
The advantage of distilled water is the consistency. Since the only molecules you have will be water, it ensures that you do not have variation in mineral content in your water. When you mix chemicals together, different molecules will react differently when put together. Reducing all other molecules and leaving only water, ensures that you are getting the chemical reactions you are looking for and nothing else.
My tap water is clean enough to drink from, can't I just use that?
Sure. You can use anything you like and if you have been developing film using your tap water without issues then why change? The problem is if you are getting some variations in your chemistry it can become impossible to track down the problem is your variables keep changing.
A proper chemistry experiment requires that you only change one variable at a time. So if you are testing three different development chemicals then you want to keep all other variables the same. The same temperature, the same water and same volumes. If your tap water is not consistent, this can make it impossible to predict your results.
Where can I get distilled water?
You can buy distilled water in gallon jugs, in smaller water bottles. It is typically a little more expensive that normal bottled water but not by much. If you look at the label you should see a 0ppm of other minerals. This means that there are 0 parts per million of other minerals in the water.
Do you use distilled water for everything in film development?
Heck no! I use distilled water to mix chemicals. So my developer, stop and fix baths are all mixed with distilled water. I rinse my film with tap water until the final rinse where I switch to distilled water to leave less streaks.
The time and energy it takes me to make distilled water ensures that I only use it when I need it. It is perfectly safe and keeps for a long time provided the container does not release chemicals into the water. I suggest glass bottles if at all possible.
What is the quantitative difference between distilled and tap water?
Ok so it is easy to say that if you spend more money on this "special" water your pictures will come out better but that is very hard to prove. The fact is that water quality will not impact the quality of your photography but can impact the consistency of your development which impacts you negative. But can we quantify the difference between distilled water and tap water?
Yes, yes we can. To do so we have to use a TDS measuring devise. A TDS measures "Total Dissolved Solids" and it measures it in PPM or Parts Per Million. For the USA drinking water is considered excellent if TDS is less than 300 ppm (or mg/L). Now this does not mention what those solid particles are. If they are arsenic (a heavy metal that can be naturally found underground) then you want much less than this. But if most are salts then 300ppm or less is fine.
My distilled water reads around 1 ppm while my tap water is close to 200 ppm. My mineral water reads about 74 ppm and the purchased distilled water reads 1 ppm. SO we have a very wide quantity of solids, now I have no way of knowing what kind of solids are they. But if I were to mix my chemicals using local tap water I run a much higher probability of having an adverse chemical reaction than if I were to use my distilled water.
Patrick...confirmed film & digital photography addict.