Both performed very well on poor paper. I expect that from iron gall inks, but I was pleasantly surprised by how well the regular Gummiberry did. The regular ink was nearly as good as the iron gall version in resisting feathering, and its lighter tone made it more resistant to showthrough and bleedthrough.
Both were incredibly easy to clean, remarkably so, considering that purple ink often is the most persistent color. Even with the pens I kept inked for six days, both inks cleaned out with only minimal flushing with water.
The two inks differ in water-resistance. As you’d expect, the iron gall Gummiberry has a waterproof core under the purple dye. In contrast, the regular Gummiberry mostly washes away. Here are water tests of both inks made on fountain-pen friendly Rhodia grid paper and lower-quality paper.
The most obvious difference between the inks is the shade of purple. Regular Gummiberry is a bright medium purple, while the iron gall component darkens the other Gummiberry. On some papers iron gall Gummiberry can look nearly black
Here are writing samples of both Gummiberry inks, bracketing standard blue and black inks.
And here is the lighter, brighter regular Gummiberry in the middle of the darker iron gall Gummiberry.
Paper towel ink chromatography shows these differences clearly, too. In the photo below, regular Gummiberry is on the left, and iron gall Gummiberry is on the right. You wouldn’t mistake these for the same ink: only the central purple area looks the same.
Each ink fills a different niche. Iron gall Gummiberry would be an easy ink to use at work, as an attractive but very dark purple. It is highly water-resistant. But it is an iron gall ink, with the extra precaution that entails.
The color of regular Gummiberry is more vivacious and fun. It’s a good editing ink, and nice in letters. Regular Gummiberry can go from pastel to medium purple, depending on how wet a pen writes. It behaves so well on notebook paper that I can see it being a good ink for school. It is not water-resistant, but it can be used in steel nib pens without worry.
I’ve enjoyed using both, and again I find myself very impressed with the small ink-maker KWZ.