Hello Sandy, i am not a chemist either but a pH of 2 is by definition very acidic, even if such levels may be common amongst inks
at the pH of 2 is for example Hydrochloric acid, which is considered a very strong inorganic acid. I do not know if the material used with pens can handle the acidity, it is entirely possible that it can, but I am certain that if you mix inks of this acidity, you may get very strong a reaction, especially if the other inks are in the alkaline range and you certainly have to wear protective equipment like glasses and gloves. It will also affect paper. Isn't acid free papers supposed to be better for archival purposes? What will be the result if you use a strong acid on a sheet of paper, even in low quantities over a number of years...
I do not intend to make light of your concerns. I apologise if I have offended you in any way.
As the chemists at work remind me, "Sandy, you're not a chemist. Get out of our lab."
The pH value is only one property of a substance; and different ink ingredients may react with different pen materials in a different way. I assume that any ink ingredients would be chosen with the intent of being 'pen safe'. (Especially if marketed in the litigious-prone USA.)
I agree that one should be careful when mixing inks. Even though the worst I've created was a dreadful gritty sludge that seemed to have a life of its own, I always wear eye protection.*
I was also struck by the apparent conundrum of how an acidic ink can be considered Archival.
To quote from Member gmrza @ Post № 9 http://www.fountainp...inks/?p=2420375:
". . . modern IG inks are more likely to have a formulation which is stoichiometrically** correct. This was not the case for historical inks - often there was excess acid which was not consumed in the oxidation of the IG compound. Excess acid is of course a bad thing.
A further factor is the kind of acid used. A lot of historical inks used sulphuric acid, whereas modern inks tend to use hydrochloric acid. Hydrochloric acid is a gas in solution, which will evaporate.
As a result, modern IG inks are less likely to damage paper than historical inks were. . . ."
* Full kit description @ Post № 7 http://www.fountainp...inks/?p=1879848)
**Wiki 'stoichiometry' http://en.wikipedia....i/Stoichiometry
Edited by Sandy1, 13 September 2013 - 08:34.