Opticz UV Blacklight Reactive Large Tip Invisible Ink Marker, Yellow

Works great, is not thick and dry, very visible. I recommended.

I got this for a scavenger hunt style escape room game. The marker works great with a blacklight pen. Just be careful going over ink that hasn't dried yet. I may have to get another one since I wasn't. On well. You may need to write with the blacklight shining, though, if you want to see what you're writing. I just kind of winged it.

The marker writes really well and shows up great with a black light, but it’s not totally invisible. If you were playing a game with kids or something, they can see the written material without the light. It looks like a very light highlighter. I still like it though.

Yellow works as advertised. Blue however is visible even without black light and identical to yellow when under black light

I routinely expel projectiles from small brass containers at a local indoor range. The containers are then ejected from my expulsion device, and fall on the floor, where they mix with hundreds, and even thousands, of similar containers.This would not be an issue, if I used containers of the same size as other hobbyists. However, most of mine are very different, and I like to recycle them, and re-use them for the same purpose at a later date.Marked with this pen, I am able to easily identify my brass containers with the use of a small black light flashlight. As a test of the concept, I marked the above brass container along the side wall, and took it outside in the sunlight, where I took this photo while aiming the black light. The bright green color really pops out, much better in real life than it appears in this picture. Since my recovery will all be indoors, I expect that recovery will be relatively easy.The amount of money I will save by getting ALL, or ALMOST all, of my containers, will be considerable.I wish there was a model with a broader tip.

I used these as part of some puzzles for an Easter Escape Room. It was readily visible on both black poster board and white cardstock. It was much more visible, glowing with the black light, but the light was not needed to read it.

The pen works well. I had to write over things multiple times but that may have just been the type of material I was writing on.

My kids love this its definitely like the one I had as a kid it works great I reccomend these markers to anyone my black light makes them glow like crazy