Cards marking is not any serect these days and many guys would like to try marking playing cards themselves. Thus the invisible ink for playing cards is quite necessary and popular.
Luminous ink is more popular that can mark the poker cards with luminous marks for infrared sunglasses or IR contact lenses to see.
Here in our company, both the invisible ink and luminous ink pens are available always.
Just feel free to contact at your convenience if you need.