Just made some more ink and used some more accurate measurements. 150 pens, 1 1/4 cups 91% isopropyl alcohol, 1/4 cups purple PVC primer. I should have either used less alcohol or just kept the brew the same, because I'm starting to notice when I add any amount of charcoal to the mix with the expectation of it becoming thicker, it just leaves hateful wet clumps in my mop. I've heard various types of powders referenced to be used as thickening agents? Are we talking like baby powder or what?