Would water make it difficult to read a tag, for instance?
Water absorbs RF energy in the ultrahigh-frequency (UHF) spectrum. So any object containing a high amount of water would absorb RF energy, making UHF tags more difficult to read. Fruit, meat, juices and the human body are all things that absorb RF energy, for example.
Carbon also absorbs UHF energy, which is why that element is used on the skin of stealth aircraft. I have heard of companies in the electronics and avionics sectors experiencing RF absorption when tracking carbon-based containers used to prevent static discharge.
—Mark Roberti, Founder and Editor, RFID Journal