Like any other wind instrument, the French horn’s biggest enemy is moisture buildup. This is due to warm air coming out of the player’s mouth touching the relatively colder environment of the horn and condensing as a result. Your foremost agenda is to dry the horn out and absorb as much of the moisture as you can, to prevent it from collecting inside and wreaking havoc. As for the exterior, be sure to wipe down the horn with a soft, clean cloth to remove marks such as fingerprints. A specialist cleaning/care kit is the perfect solution.