Sparky;
I apologize if my words could be misread, but the sum total of your first two posts ask and state "if anyone has used a dish detergent - you can if you choose wisely". This is a summation of what you asked, not an exact quote.
You went on to comment on the use of the pH of a surfactant affecting the stability of paper.
So, my answer was that dish detergents commonly contain alkali, perfumes and colorants, and that some of them contain skin conditioners (oils) to prevent chapping of hands. I further stated that you do not commonly use a surfactant at all when processing papers. I think that this addresses all of your comments.
Now, let me separate buffer capacity from pH. They are two different things. Buffer capacity can refer to acidic or basic solutions. It is the resistance of a solution to a change in pH from the present pH value, whatever it may be.
Water, whether alkaline or basic has little buffer capacity as the level of chemicals is so low. It can normally range from about 6 - 9 with an average of about 7. Recently though most cities have begun to adjust the pH to alkaline values to reduce pipe corrosion.
A washed film will be at the pH of the final wash water, whatever that may be. During drying, the pH generally drops towards the acid region due to the carbon dioxide in the air and it then stops as the water evaporates and stabilzes at some indeterminate value. This is usuall pretty close to neutral.
Photo flo, (which I use BTW) is made from organic compounds that do not form crystals when dry and which do not change the pH of the coating. Ionic surfactants such as used in detergents are also organic, but can leave deposits on the surface of film. This is because they are salts of organic chemicals, such as the sodium salt of di-nonyl naphtalene sulfonic acid. As such they can form a soapy scum if left on film. This is why you use things like Tilex to remove that soapy scum from the shower or bath. These are a mixture of dried soap and calcium salts formed with the soap. It also includes skin oils and the detergent oils and scents.
Therefore, even at a drop in a liter of water, there is enough potential (potential <- see that) to form a scum from a lot of sources that dish detergent or soap is not advised for use.
There are many excellent wetting agents out there besides Photo Flo. They include a variety of surfactants designed to make no change to the pH of a film and leave no scum on the surface. Use them instead of dish detergent or soap. Never use automatic dishwasher detergent.
PE
