The unique ink is based on a secret formula developed by KGB scientists during the Cold War period, and has been recently adapted into a modern gel pen format. This is the genuine disappearing "spy ink" pen - don't confuse it with the fabric marking pens (usually having purple ink and a felt-pen tip) or novelty pens that others sell as disappearing spy ink pens. Despite its unique capabilities, this pen looks and writes exactly like a regular pen and writes in a standard dark blue ink. Since it's a gel pen, it writes smoothly with a continuous flow, and has a long shelf life. It has a popular 0.5mm point size. It requires almost no downward pressure to write on the paper, so it's not necessary to leave indentations on the paper that could possibly be used to reconstruct what was written. Once on paper, the ink appears normal for about 15 minutes. Then it begins to slowly deconstruct. After about an hour, it will have mostly disappeared, but will still be slightly visible. After about 24 to 48 hours it will have completely vanished! (Fade time and characteristics may vary depending on ambient environmental conditions.) Even an inspection under ultraviolet light will come up with nothing. (Fade time and characteristics may vary depending on ambient environmental conditions.) Now you can write confidential or sensitive notes on documents and be assured that they will be gone later. Great for those occasions that you want to say something - temporarily.