This is my first commercial iron gall ink purchase and so far I love it! I specifically bought Rotring Surf (with medium nib) and Parker Vector (fine nib) fountain pens to accommodate this ink, as I've heard iron gall inks tend to write dry and these are wet pens. This ink does indeed write well in both pens. The Parker Vector fine nib writes more like a medium nib with this ink (at least on the Office Depot inkjet paper), and the Rotring Surf medium nib writes more like a fine nib.
According to Xfountainpens where you can get this ink, this is repackaged Diamine Registrars Ink. It comes in a 50 ml (2 oz) Nalgene leak-proof bottle, and is a great bargain at $9.95 (with free shipping over $15). I'm not affiliated with Xfountainpens; I'm only a first-time but satisfied customer. I don't know if anyone else sells this repackaged ink or not. It is cheaper than Diamine Registrars Ink.
I tested the ink on both Office Depot Inkjet and Strathmore Parchment 100% rag. It flowed best on the cheaper Office Depot paper. It felt dry on the 100% rag paper, but there were no skips in the ink flow. There was no feathering or bleedthrough on either paper. The ink goes on blue. I'm wondering at what point it will turn black? The ink dries within 4-5 seconds (I'm a lefty but didn't have any smudging problems with the ink). This ink is waterproof. It oxidizes black after wetting (and presumably with time, too). I forgot to mark on the sheet that there was no nib creep or build-up. (Edited next day: I checked the nibs, and both had nib creep.)
I've never bought commercial iron gall ink before. I have made homemade iron gall ink, which goes on pale brown (almost invisible) then quickly turns a jet black upon drying and it's a fun transformation to witness. I don't notice this same kind of transformation as I write with Chesterfield Archival Vault (at least not yet), though my own inks do not have blue dye added to them (which is probably what delays the transformation in the Chesterfield ink). It did turn black after wetting it.
All in all, I'm delighted with this ink. I'll be doing sunshine tests on it next and will post in the future how it holds up.
ETA: forgot to add one last image:
Edited by fiberdrunk, 24 December 2010 - 17:17.