As a user of Konrad's inks, permit me to add a personal comment. First of all, when you purchase his iron gall inks, Konrad includes an instruction sheet (usually,) that gives you all the caveats for iron gall. Please note that this is ink made the way ink used to be made, with ground up gall nuts (usually from oak trees,) iron filings, and a few other ingredients. This ink was in popular use when quill pens were the norm. These were disposable, and so any potential for harm to the pen itself was irrelevant. With your expensive fountain pens, there is, or at least, may be an issue. Iron gall inks have potential corrosive properties. Konrad notes that he formulates his inks to avoid or minimize these properties, but the potential is still there. If you're filling a good pen, one that is valuable or means something to you, with iron gall ink, give the pen a shake now and then, and by no means permit the ink to be in the pen longer than a week to ten days. At that time, flush out your pen thoroughly and carefully clean it. Water works perfectly well. You can then refill your pen with iron gall ink, as long as you continue to follow the regular flushing procedure. It's great ink--just be careful when you use it. There's a reason why we switched to water based dye or pigment inks, and as always with new technology, something's lost and something's gained. If you buy it, enjoy this truly great ink.