By Jerry Banks and Les G. Thompson, co-authors of RFID Applied

Under ideal conditions, the popular Alien Squiggle RFID tag can be read at a distance of approximately 20 meters. But what happens if it is placed behind a glass of water? What about placing it to the side, but adjacent to the glass of water? How about placing it in the water?

Answers to these and other questions will appear later, but suffice it to say that the readability of a tag is affected by the placement of the tag and its ambient environment.