Hello All,
I came across this table a while ago, some of you may have already seen this. I find it interesting and will now carefully select certain inks for use in my precious vintage pens. You will have to zoom in on the pic to read clearly.
A point to note is that WM Havanna Brown (one of my favourites and currently loaded in to my Sheaffer 1927 flat top) has a -ph of 7 = same as water.

Ooops sorry for the large pic, you will have to copy and then read to see all at once.

I think all Noodlers are pH 7 (certainly Black is) so they should be "safe" as well.

I would very much doubt that pH by itself determines the "safety" of the ink. Safety to what? To the nib or to the paper?

The only scientific reason that low pH is "bad" is that it may react with the paper as it dries. For example Pelikan Royal Blue tends to fade on some paper. I understand that paper needs to be alkaline for preservation reasons but that could spell "trouble" for low PH inks.

I have also heard that it is not the pH by itself that is important but its stability. If it drifts, the viscosity may change - for this they add "buffing" compounds to the ink.

In any event, I do not claim to be a chemist and sometimes half-knowledge is worse than lack of knowledge. So I would vey much like to hear a "true" chemist to explain all these to us.

Till then here some interesting links for inks
Glenn Markus ink page
Rumors and BS about Ink from G. Clark (Inksampler)