So I've recently joined the ranks of vintage pen lovers with my (new to me) Greg Minuskin stubbed Parker 51. I adore the pen, but when I purchased it, I was strongly cautioned against using Noodler's inks. Noodler's has been in regular rotation for me since I got into fountain pens in a serious way about 5-6 years ago. I've been using it regularly in my Pelikan and Edison pens without problem. Now that I have the Minuskin 51, I have the vintage pen bug and want to buy more, but I'm concerned about inks. I also miss (and quite frankly could use) the water resistance of my old favorite inks. While Googling, I found this: http://www.marcuslink.com/pens/ink/ink-and-ph-levels.htm Now, Mr. Minuskin advises using inks from only pen manufacturers. He specifically says Pelikan and Waterman inks are fine. According to that chart, Pelikan inks are up there on the acidity levels compared to some other options. So if it isn't the pH that eats the sacs of these vintage pens, what is it? Which inks are safe, and which aren't? I can't afford to re-sac all my pens every 6 months.