An applicator includes: an applying part on a front portion thereof; a removable cap that totally covers the applying part; a sealing element that seals up a front end portion of the applying part when the cap is fitted; and an inner cap provided inside the cap. The inner cap includes an inner cap body and a hinged cap that is joined to the inner cap body and can abut the inner cap body. The hinged cap has a hollow mounting portion. An engaging portion for fixing the hinged cap is formed inside the cap. When the inner cap having the sealing element held between the inner cap body and the mounting portion is fitted into the interior of the cap, the hinged cap is engaged by the engaging portion inside the cap.

An ink composition includes a fluid and a plurality of microcapsules suspended in the fluid. The fluid includes a first chemical compound that exhibits a first color characteristic in a first pH range and exhibits a second color characteristic in a second pH range, where the first color characteristic is visually distinct from the second color characteristic. A second chemical compound is contained within the microcapsules, such that rupturing at least a subset of the plurality of microcapsules releases the second chemical compound. Releasing the second chemical compound shifts a pH of the fluid from a first pH in the first pH range to a second pH in the second pH range.

An ink composition includes a fluid and a plurality of microcapsules suspended in the fluid. The fluid includes a first chemical compound that exhibits a first color characteristic in a first pH range and exhibits a second color characteristic in a second pH range, where the first color characteristic is visually distinct from the second color characteristic. A second chemical compound is contained within the microcapsules, such that rupturing at least a subset of the plurality of microcapsules releases the second chemical compound. Releasing the second chemical compound shifts a pH of the fluid from a first pH in the first pH range to a second pH in the second pH range.

An ink composition includes a fluid and a plurality of microcapsules suspended in the fluid. The fluid includes a first chemical compound that exhibits a first color characteristic in a first pH range and exhibits a second color characteristic in a second pH range, where the first color characteristic is visually distinct from the second color characteristic. A second chemical compound is contained within the microcapsules, such that rupturing at least a subset of the plurality of microcapsules releases the second chemical compound. Releasing the second chemical compound shifts a pH of the fluid from a first pH in the first pH range to a second pH in the second pH range.

An ink composition includes a fluid and a plurality of microcapsules suspended in the fluid. The fluid includes a first chemical compound that exhibits a first color characteristic in a first pH range and exhibits a second color characteristic in a second pH range, where the first color characteristic is visually distinct from the second color characteristic. A second chemical compound is contained within the microcapsules, such that rupturing at least a subset of the plurality of microcapsules releases the second chemical compound. Releasing the second chemical compound shifts a pH of the fluid from a first pH in the first pH range to a second pH in the second pH range.

A writing instrument includes a first reservoir for dispensing a first fluid having a first property of reflectivity. A first tip member is in fluid connection with the first reservoir. The first tip member has an end with a size and shape that corresponds to a response area of the response form. A second reservoir can be used for dispensing a second fluid, which is capable of modifying the first property of reflectivity when covering the first fluid. A second tip member is in fluid connection with the second reservoir. The second tip member has an end with a size and shape that corresponds to the response area of the response form.

A writing instrument includes a first reservoir for dispensing a first fluid having a first property of reflectivity. A first tip member is in fluid connection with the first reservoir. The first tip member has an end with a size and shape that corresponds to a response area of the response form. A second reservoir can be used for dispensing a second fluid, which is capable of modifying the first property of reflectivity when covering the first fluid. A second tip member is in fluid connection with the second reservoir. The second tip member has an end with a size and shape that corresponds to the response area of the response form.

An ink composition includes a fluid and a plurality of microcapsules suspended in the fluid. The fluid includes a first chemical compound that exhibits a first color characteristic in a first pH range and exhibits a second color characteristic in a second pH range, where the first color characteristic is visually distinct from the second color characteristic. A second chemical compound is contained within the microcapsules, such that rupturing at least a subset of the plurality of microcapsules releases the second chemical compound. Releasing the second chemical compound shifts a pH of the fluid from a first pH in the first pH range to a second pH in the second pH range.

An ink composition includes a fluid and a plurality of microcapsules suspended in the fluid. The fluid includes a first chemical compound that exhibits a first color characteristic in a first pH range and exhibits a second color characteristic in a second pH range, where the first color characteristic is visually distinct from the second color characteristic. A second chemical compound is contained within the microcapsules, such that rupturing at least a subset of the plurality of microcapsules releases the second chemical compound. Releasing the second chemical compound shifts a pH of the fluid from a first pH in the first pH range to a second pH in the second pH range.

A decolorizing apparatus includes a translucent heater, a casing, and a controller. The translucent heater is configured to generate heat according to an applied voltage. The casing is configured to support the translucent heater. The controller is configured to apply a voltage to the translucent heater. The voltage is associated with a temperature at which a thermochromic colorant.