I think that safety razor is washable due to its compact size. The full size single blade razor need to be dunk in antiseptic fluid. This fluid is the same blue liquid used by the traditional barber.

The full size razor blade tend to get rust quickly if its blade isn't well maintained. All barbers use this antiseptic fluid to clean the blade and prevent it from rust. The blade will rust if it is left exposed to the air for long period.