Ink is waterproof after drying, so you should rinse the nib with clean water immediately after use. Dry the nib very well afterward to prevent it from rusting. Avoid holding the nib and nib holder under the faucet, water can get into the globe of the nib holder and cause rust. The nib holder itself should also be cleaned of ink residue with a damp cloth and dried well. Wooden models in particular do not like moisture in the long term.