It’s been almost 10 years since I entered in the amazing world of rapidographs and chinese inks. Back when I was in high school, my drawing teacher taught me how to difference good inks from the ones that led your rapidographs to an inexorable death. From what I’ve learn, there are two types of bad inks: The ones that are so diluted that make the rapidograph drown and look like it’s throwing out all the ink, and the ones that are so dusty that it seems they exist just to obstruct and kill your precious rapidograph.
So, how can we know and ink is bad before we even make the purchase? It’s pretty easy, for the diluted ones, you just have to look the consistency of it, chinese inks tend to be a little viscous, so if you see the ink moves like common water, you’re in front of an diluted ink. For the dusty inks, you can see them through a good light, then you’ll know if it’s dusty/old; I had one like that, and It almost kill my rapidograph, luckily I realized what was happening before it were too late. So that’s it, hope these little advices help you to find the best ink for your rapidograph. Goodbye!