For most pens, a simple flush with cold or room temperature water (NOT hot) will be enough to prepare your pen for storage or a new ink color. Simply use a converter to force water through the nib unit. For particularly stubborn pens we recommend that you use our Anderson Pens Pen Flush when cleaning your fountain pen. You can use the Pen Flush regularly, after every 3-4 ink refills, or when changing ink colors, or you can also use it to soak a clogged nib and feed overnight.