One of those curious questions that occasionally pop up on the tarot forums (with what I sense is a faintly scandalized tone), and a real head-scratcher for old-timers at this stuff, is “Do you let other people touch your cards?” The assumption is that a troubled sitter’s “negative energy” will bleed all over the cards, which will absorb and retain it, becoming unreliable for future readings. The more pragmatic among us will say that the cards are only tools made of ink and cardboard with no personality (much less a psyche) that can be permanently corrupted by “bad vibes.” Any psychic energy they may harbor is put there by the client (or the reader in self-readings) during the act of focusing on the question, and evaporates on its own when the reading is over. So there is really no need for mystical ablutions like smudging, moonlight or candle-light “washes,” prayers, mantras, magic-wand-waving, or other fanciful means of cleansing, which only serve to make the diviner feel good.
Back when reading tarot for the public was almost exclusively an interactive art conducted in face-to-face sessions (there may have been occasional “snail-mail” exchanges but I never heard of one), it was a given that a sitter would shuffle and cut the deck. Having the reader do so instead because of a concern that the cards would be irretrievably damaged in more than a mechanical way by being placed in the grubby paws of the potentially unwashed (either physically or spiritually) would have defeated the purpose of letting the querent converse subconsciously with them as a prelude to the reading. Understandably, If your only deck is a cherished, ultra-rare “Pam A” RWS, you’re not going to take it out of the house, never mind let anyone else touch it. But the solution to that is to buy a couple of inexpensive, readily replaceable decks since a competent reader can work effectively with almost any of them. Anyone who isn’t tough-minded enough to fend off the risk of psychic contamination (including not just card adulteration but the even more insidious “psychic vampirism”) should probably be in a different business.
Personally, I expect my sitters to handle the cards, since it’s a large part of how I think tarot “works” and it actively engages the client in the reading, instilling ownership in the outcome. Until I came across the notion that it might not be a prudent thing to allow, it never would have occurred to me to do otherwise. Not only do I see it as an essential step in the process, it’s also a part of what I call the “theater of tarot” that gives the sitter a major role to play. Although I know others have done so, I’ve yet to meet a sitter who was squeamish about participating when I put it that way. My assumption is that the concept of deck corruption came from some of the relatively modern tarot writers who are decidedly more mystical (I won’t denigrate it by calling it “woo-woo” but the thought is certainly lurking) than practical in their approach.