A new “class” of writing ink, whose ink has new chemical features, is being introduced into the United States from Japan. The new ink is known as gel ink and it is water-based. It can be differentiated from the traditional water-based roller ball and porous tip class of writing inks by its chemical composition and physical properties. Gel inks differ from other water-based inks by the incorporation of colored pigments to give the inks a full range of colors without the use of colored dyestuffs commonly used in water-based inks. Other differences include gel ink's high viscosity, leading to the name “gel ink.” The gel pen is visually identifiable and different in appearance from other writing instruments by its clear outside barrel and fill tube, which contains the pigmented gel ink. The pen housing and fill tube is clear in order to display the actual color of ink. The plastic fill tube will be a larger diameter than the tube found in a ballpen and will contain a clear silicon grease plug. Gel inks are tested and differentiated from other writing inks by the same battery of tests used in the past. Nondestructively, gel pen writing can be visually examined for ink absorption into the paper fibers, color difference and overall line quality of the writing. Ultraviolet and infrared light examinations will also aid in differentiating gel inks from other writing inks. Destructive methods of testing gel ink may prove to be the most identifiable and demonstrative of all the available tests. Thin layer chromatography may be used to separate detectable components of inks. Gel inks that contain pigments and no dyestuffs for separation, will have a negative reaction in this area. The gel pen is a unique writing instrument because of the chemistry in the gel coupled with a new pen design. The water-based gel ink is environmentally friendly and permanent. These attributes may allow the gel pen a sizeable impact on the U.S. market.