L81 has made only one of the I tested UV lamps an invisible pattern visible on my bathroom tiles!

First of all, one thing that has irritated me. The description says, this is the L81 a double UV lamp. I was therefore assumed that would include the two lamp UV lamps. It is a UV fluorescent lamp and a so-called "UV" diode. No Matter. I have tested the fluorescent tube to documents (100 Icelandic crowns, 10 DM (new license), old personal identity card, passport and new identity card). The result was not as excellent as in another UV lamp to light tube base. The UV-drawing on the new ID card was not brought to light. But, by chance I took the UV lamps in my bathroom, and because the L81 had their finest hour: A, invisible to the eye, drawing on the tiles came well to bright days. This means that the UV lamp operates in a still higher Frequenzberech.