The structure of the Kuretake Fountain Hair Brush Pen is basically the same as a regular fountain pen, with an ink cartridge inside and a brush end nib.
Sometimes the ink in the brush nib can harden after a long period of no usage. If this happens, you can take the following steps to get the pen going again:
1) Remove the ink cartridge from inside the pen barrel.
You can save a full ink cartridge by covering the opening with some scotch tape and storing with the opened side up.
2) Soak the brush pen nib in room temperature or warm water. Make sure to change out the water when it is saturated with ink, until the water is no longer black. (1-5 days)
Please do not remove the metal part or disassemble the brush part, in order to prevent ink leakage.
3) Rinse the clean brush nib with running water, and remove the excess water using some tissue. Leave it in a shady spot for a day or so, to let it air dry.
If you put the nib back before it is dry, the ink may leak from the side.
4) Insert a new ink cartridge.
After you insert the ink cartridge, the writing might be a bit weak in color due to the moisture left in the brush nib. If you keep wring for a while, the color of the ink will go back to the original color.
To avoid this pen drying out in the first place, Kuretake recommends to use this pen often, without a long period of no usage. Also when you finish writing, they recommend to lightly dry any excess ink off the nib with some tissue before you put the cap back on.