Today's yellow ink is Private Reserve Buttercup. This ink comes in 66 ml bottles for $11 so it's one of the more cost effective inks. I don't remember where I purchased my bottle, but you can find it for sale at Anderson Pens.
Buttercup is a bright spring yellow.
This ink goes down very light yellow, and darkens as it dries.
Let's take a look at how the ink behaves on fountain pen friendly papers: Rhodia, Tomoe River, and Leuchtturm.
Dry time: 40 seconds
Water resistance: Low
Show through: Medium
On 20 pound copy paper the ink behaved well, no issues that I noticed.
I used a medium Pelikan M800 Renaissance Brown on Tomoe River paper. The ink had an average flow.
Overall, I think this is a nice spring yellow. It's dark enough to be read but still pretty bright. I think it's probably too light and bright for most uses, but it might work well as a highlighter ink. Give it a try, you might love it.
Disclaimer: I purchased this ink myself, and all photos and opinions are my own. There are no affiliate links on this page.