One of my pen club pals Katie, swatched all the inks at our local pen shop using a rubber stamp. The effect is eye-catching and makes a quick way to show ink without using a big brushy swab.
While in Canada I found a couple stamps from Chamilgarden at PaperPlusCloth. I found a checked pattern similar to what Katie used and a dot design. Using a paint brush, I brushed ink onto the stamps and then pressed them into the paper. Some inks filled in a bit, others kept the stamp design more cleanly. It could also be a user error since I don’t work with rubber stamps ad fountain pen ink much. Though it was a lot of fun to try and each result was a little different and unique.
The sparkle ink I tried filled in a lot more though I suspect is had something to do with the gold particles. It gave a nice representation of the ink including shading and the sparkle. The other tests I did showed variety in the ink and the checked pattern stamp mimicked varying line widths nicely. I need to improve my implementation though.
While Chamilgardden stamps are pretty hard to come by, a search on Etsy for “grid rubber stamp” or “background rubber stamp” offers some other options.