There has been a few cases of urushi coated grip section deterioration.
mostly the deterioration occurs with the clear types of urushi finish.
the clear outer coating of urushi will change into awful looking light brownish color.
the durability will be reduced as well.
at first i thought, maybe the quality of the urushi is the problem.
however, i only use high quality urushi from Japan.
moreover evidence proves that only the grip section is deteriorated, while barrel and cap are perfectly fine.
therefore, my logical conclusion is the high humidity inside the cap.
i've also consulted urushi expert on this matter.
he said: "based on my long experience with urushi, i've never seen cured clear type urushi change into that light brownish color due to humidity. however, normally urushi coated objects never gets exposed to long duration of very high humidity. So i cannot say humidity is not the cause for this."
so, based on these i concluded, although urushi is a natural waterproof material, long duration exposure to very high humidity ( > 90%) will compromise the urushi coating.
the extremely humidity will be similar to getting completely soaked with water.
and the long duration will allow water to penetrate into the urushi layer, all the way down to the ebonite surface.
therefore this is how you prevent such phenomenon from happening:
1. Use the urushi pen regularly, when the ink is filled.
everytime you open the pen, the humidity will drop to regular level.
when the cap is closed again, the humidity will rise slowly, until you open the can again.
this will help regulate the humidity level inside the cap, preventing extremely humidity.
2. when the urushi pen is not going to be used for a long time (more than week~months),
you must flush the pen with water,
then store the pen with the cap open, to facilitate drying and prevent humidity build up.
although we cannot prevent 100%,
following these 2 simple instructions will greatly help to prevent urushi deterioration of the grip section.