OpticzIndustrial Invisible Blue UV Blacklight Reactive Security Ink (4 Ounce Bottle)

Works well. Note, the package says not for use on skin. The company sells skin-safe ink too, so make sure you order what you need. I was going to simply use a fingerprint. Instead I used a rubber stamp.I used this to put a security mark on documents. Much faster and cheaper than using a UV marker that tends to dry out quickly.

we used this to mark the back of playing cards with painted numbers. Worked perfectly.

It works nicely, however its alcohol based so it can dry up if not covered on the stamp pad.

My need is to quickly identify previously marked small brass containers, which are mixed in with other brass containers. All of these are at a distance of six feet from my eyes, in a large room illuminated by standard fluorescent light. I use a black light flashlight to make the UV pop out.I have previously used UV markers and fingernail polish to mark the individual brass containers prior to use, and this has worked well. However, that DOES require a labor-intensive, individual application of the ink/polish to each container, as well as some drying time. In addition, the nail polish CAN interfere with proper function of the brass containers, if applied too thickly.My hope was that by using this product in a spray container, I could mark a large number of containers at once.In the picture, is is clear that the invisible ink DOES pop out on OTHER surfaces, which are wax paper and a wood table top. However, the brass containers have, at best, a light, mottled appearance, making this useless for my application. I included one filled brass container, marked with nail polish, in the picture, to show the results I was hoping to match. As you can plainly see, it wasn't even close.I believe this could be useful in many other applications; it was useless to me. I am glad that I restrained my enthusiasm, and only purchased a small-size container.