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Cobby33ANYTHING you do to a card from the time it reaches your hand, to the time it leaves your hand.  I would except: putting in and out of protective holders and brushing off superficial substances such as dust, pet hair, etc.  
Not sure about pizza sauce, though if it doesn't leave a mark without having to add water, etc., then I suppose that's ok.  Some pizzas I've eaten taste like pizza sauce on cardboard anyway.