[mrob]

You can get fountain pen inks that chemically react with cellulose for complete water resistance (there may still be a little smudging from unreacted ink washing off the paper). Noodler's Black is a famous example. I like this kind of ink, although it's not without its drawbacks, because cotton/rayon/other plant fiber clothing is also mostly cellulose and will be stained just as permanently.

[bikenaga]

I've used only Noodler's Bulletproof Black for years (in a TWSBI Eco piston-fill) - it works great, and I realized if I was going to take the time to write extensive notes it was worth having some protection against water.

I previously used Waterman Black - it flows really smoothly, but it isn't waterproof. Also, it doesn't seem quite as dark as the Noodler's.

[specialist]

> inks that chemically react with cellulose

I had no idea. Great tip; thanks.

I'm looking for alternatives to lamination for posting outdoor flyers & signs.

I just received some (alleged) weatherproof copier paper to experiment with.

https://www.amazon.com/dp/B01MQ3UNWL