I bought a bottle of Diamine Woodland Green, but find it a little bright for my taste. I'd like to know if I can safely add a little Noodler's Bulletproof Black to give it a more olive appearnce?

Odds are this is totally safe. But weird things have happened.

People around here always say to mix it up and let it sit for a day or so and see if you notice any sludge or solid particles--before you put in any pen you'd mind replacing or would have trouble replacing. (Or you could just mix it up and use it and not worry about it in some $4 pen.)

I'd mix it in a converter or a cartridge. I used small vials until I got that idea from Melnicki.

Let us know how it turns out.

Thanks, I'll do that. It makes sense that if I don't see any precipitate after a day, it should be fine.

I'll second that last reply. ..Wait a day or two before loading.

Friday I mixed Noodlers Polar Blue, a BulletProof, with Noodlers Navy, a Near BProof, and the color was quite nice. Wrote well for a couple days, then the pen I'd put it in, a Parker Vector, normally a free flowing pen, just wrote... "sticky". There was still a half cartridge full of ink. Added a drop of two of water... didn't help. I'm now cleaning the pen and cartridge with water and small soap.

I believe the problem was both inks have permanent properties, maybe not the same type. Together they made pretty cement.

Further suggestions on cleaning are welcome.
SallyLyn

Even if nothing bad happens to the ink, I would still try to mix a little bit before mixing the whole bottle. I wanted to darken up some diamine sepia. Tried it with a bit of Quink black. The ink was fine to use but it turned out green. Luckily I just mixed a bit and not the whole bottle at once.