As a test a year ago, I wrote some stuff down in YE MOFT HOLIE #GRIMOIRE (an unused #journal I had laying about, as you do) using some black light reactive (#uvink) pens, because that's cool.

so if you're considering this, you need to know that the ink WILL bleed. Not outwards (the text is still pretty well defined) but up and down. The pages preceding the page with the text and after it all have ghosted imprints of the text on them. The backside of the page is almost a mirror image.

Cool effect, and one you can work with. Happy accidents and all that. Just don't set down to writing a lengthy manuscript in #blacklight ink over multiple pages and expect it to be readable ("archival") in the future.