This is the first of a few Pennonia fluorescent ink samples I bought, Napnyugta/Sunset. From the product listings they appear darker than highlighter inks, so more useful, but still react to UV. This one is sort of a peach-ish orange. Hit it with UV, though, and it glows bright orange. The chromatography strip glows more yellow.

I really like this one, it’s one of my current favorites.

Update from 2026: I’ve refilled one pen with this ink more than a dozen times since buying a bottle, and used it in several others as well, all with great success!

Scans

The scan of Iroful is fairly accurate, the others are a bit more pink-ish and less orange than they should be.

Scan of an ink swatch card made from Col-o-ring paper — Swatch Card Scans. Click to enlarge.

Scan of an ink swatch card made from Iroful paper — Swatch Card Scans. Click to enlarge.

Photos

These photos show each swatch under natural light, a mix of natural and UV light, and UV light alone.

Col-o-ring paper is very reactive to UV and the paper itself glows blue brightly, which makes the glow of the ink appear less intense. Iroful is mildly reactive to UV and glows a little. MD reacts very low so it shows off the glow of the ink the best.

A mix of UV and natural light seems to yield the best results to the eye.

The photos are closer to what it looks like to the eye. MD looks a lot more orange than the other papers, Iroful leans more toward peach. In all cases the fluorescent glow is definitely orange and intense.

Microscope

Ink under Magnification. Click to enlarge.

As with the photos, Iroful is more peach, MD is more orange. Notably, the paper fibers visible in Iroful are more orange as well.

Microscope UV

These photos show magnified portions of each swatch under natural light, a mix of natural and UV light, and UV light alone.

Microscope UV photos are a bit tricky since I have to dial the light up/down on the microscope and add UV light from a flashlight. As the UV light intensifies, it seems to play tricks with the microscope’s camera with the background to some extent.