For ongoing cleaning, a lint-free cloth suffices; if needed, a moistened nail brush also helps. Jewellery-cleaning or ultrasonic baths are taboo, because they destroy leather straps and depending on the model can impair water resistance. Only Montblanc sports watches with a screwed crown tolerate an ultrasonic bath reasonably, yet here too it is expressly advised against. For thorough cleaning, the watch should be sent to Montblanc service.