Opticz UV Blacklight Reactive Large Tip Invisible Ink Marker, Yellow

I bought this to help make UV geocaches. The ink works great, and I believe it works as intended, but it seems UV ink on paper can smear if it gets wet. Easy to use and read with a UV light.

Used this in a student project with our robotics class to create an “escape room”. We used it on a blackboard in a dark area, with some text written in chalk and the other text with this pen. It worked great.

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.

I bought this to put duplicate hidden numbers on documents. It works very well. On the first few uses, the tip has a little more ink than needed, but I solved that my standing it up with the tip at the top. Don't expect as much coverage from say a Magic Marker or Highlighter. This has started to dry out after writing 350 half inch tall numbers. I ordered some more so I can finish my documents consistently. If you do not have to write with it and only need to mark, consider buying a small bottle of UV ink for a stamp pad, a non inked pad, and a rubber stamp with a suitable shape. I ordered all these from Amazon for the cost of two of these markers. This did work exactly as promised, and I am pleased with how they work. I also highly recommend the "Dark Dawn" UV B light sources. They are true UV B, rechargeable, have a good run time, and you cannot beat the price!

So I had this great idea to grab this marker out of my bag and write on some of my drunk friends faces. Well this marker does not wash off easily. Sharpies are easier to wash off. Anyways they got me back and I’ve taken one shower and washed my face and it’s still there under UV light. Looks like this is will stay on for about a week and will fade with each shower. Do with that information as you will. Have fun bros.

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.

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 had a case where I needed to secretly mark my work to knowafterwards if somebody had tampered with it. It worked for me as I had taken pictures from before I got a claim, and after I reviewed, I could promptly determine the claim was not valid.