One popular choice for calligraphers who are looking for something beyond a standard black ink is to try walnut ink. The liquid walnut ink that is for sale on our website (I53) is a lighter sepia shade, that while looking beautiful is not always as dark a shade as one might desire. We now have available an additive for the walnut ink, (I53-DRK) darkening medium, which allows you to control the desired shade.
I53-DRK. Walnut Ink Darkening Medium.
The darkening medium is not an ink but an additive to be used to darken the original ink without losing the unique watercolor characteristics or the ability to lift color or lighten areas.
The darkening Medium is very heavily pigmented. It can also be used straight from the bottle. However, it is so heavily pigmented that it will behave like a sumi ink and stain the paper and not lift as easily as the original.
Check out this Instagram post to see the walnut ink darkening medium in action: