A nib for a refillable free ink writing felt pen includes a body and a dry ink tank including dry ink, the dry ink tank being delimited by the body of the nib and a dry ink tank wall including a water-soluble film.

A nib for a refillable free ink writing felt pen includes a body and a dry ink tank including dry ink, the dry ink tank being delimited by the body of the nib and a dry ink tank wall including a water-soluble film.

A nib for a refillable free ink writing felt pen includes a body and a dry ink tank including dry ink, the dry ink tank being delimited by the body of the nib and a dry ink tank wall including a breakable portion.

A nib for a refillable free ink writing felt pen includes a body and a dry ink tank including dry ink, the dry ink tank being delimited by the body of the nib and a dry ink tank wall including a water-soluble film.

A nib for a refillable free ink writing felt pen includes a body and a dry ink tank including dry ink, the dry ink tank being delimited by the body of the nib and a dry ink tank wall including a water-soluble film.

The present disclosure relates to writing instruments which are charged or recharged with a water-based ink composition. The water-based ink composition may be prepared from solid ink compositions which may be diluted with water. The solid ink composition comprises a specific combination of polyethylene glycol, at least one coloring agent and a humectant.

The present disclosure relates to writing instruments which are charged or recharged with a water-based ink composition. The water-based ink composition may be prepared from solid ink compositions which may be diluted with water. The solid ink composition comprises a specific combination of polyethylene glycol, at least one coloring agent and a humectant.

A refillable free ink writing instrument including a body having a rear end, a front end and an ink reservoir disposed between the rear end and the front end, a writing tip mounted on the front end and a plug mounted on the rear end, wherein the plug is configured to close an opening in fluid communication with the ink reservoir, the plug being configured to be removable from the rear end to refill the ink reservoir with water and concentrated ink refill.

A refillable free ink writing instrument including a body having a rear end, a front end and an ink reservoir disposed between the rear end and the front end, a writing tip mounted on the front end and a plug mounted on the rear end, wherein the plug is configured to close an opening in fluid communication with the ink reservoir, the plug being configured to be removable from the rear end to refill the ink reservoir with water and concentrated ink refill.

In a first aspect, the present disclosure relates to a system comprising a writing instrument, wherein the writing instrument comprises a solution of one or more salts and a writing orifice. Furthermore, the system comprises a drawing substrate configured to change color based on the concentration of the one or more salts and/or water content, wherein the drawing substrate comprises cholesteric liquid-crystals.