Under normal circumstances, condensate from the heated body and breath evaporates by itself. But if you put it immediately into a case or leave at high humidity, the instrument starts rusting. Well, there is nothing terrible but the look may be ugly. Instruments made of steel need to be wiped dry with any cloth or tissue after playing. Use of alcohol is not necessary. Disinfectants are not for drying metal. In the most humid conditions it can be lubricated by any oil (of course, tea tree oil is much more pleasant than machine oil).
If rusting occurs, you can polish the surface with polishing paste. But don’t overdo it with the paste, as long as a layer of metal is removed during polishing. Which can change the sound of instrument and reduce its resource.
Almost all metal Jew’s harps darken over time and the ones made of brass darken faster. And the speed of rusting may vary with different people and in different situations due to differing composition of sweat, saliva and humidity. You don’t have to rub it to a shine all the time for the reasons listed above. Although, if you really like it, of course, you can. 😉
In order for the harp to last longer, it is necessary to control the plucking force while playing. In addition, different models have different durability, inhomogeneity of the material leads to severe abnormalities in this parameter.
Keep an eye on the instrument response to increasing of effort: the volume increases unevenly, its growth is reduced when approaching dangerous boundaries. When, after increase in plucking force increase in volume is barely noticeable, it is better to stop and go a couple of steps back. Overloading leads to irreversible changes in the structure of the metal reed, it gradually starts breaking down and after some time can break even with a light touch.