Pens comprise a non-aqueous writing ink comprising a solvent, a coloring agent, a resin, a gelling agent, and a homo or copolymer of vinylpyrrolidone and/or a polyvinyl alcohol which is acetalized with an aldehyde comprising between 1 and about 6 carbon atoms, wherein the gelling agent is a mixture of silica particles and of a fatty acid amide wax, wherein the homo or copolymer of vinylpyrrolidone, if present, is present in amounts of between about 0.05 and about 0.6 wt.-%, relative to the total weight of the ink and wherein the polyvinyl alcohol which is acetalized with an aldehyde comprising between 1 and about 6 carbon atoms, if present, is present in amounts of between about 0.05 and about 1.0 wt.-%, relative to the total weight of the ink.

A clathrate of 1-methylcyclopropene with α-cyclodextrin, obtained as a solid particulate product, is modified by comminuting, classifying, or both to obtain a modified particulate. When subjected to identical atmospheric disgorgement conditions of humidity and temperature, identical masses of the modified and unmodified particulates exhibit different rates of 1-methylcyclopropene disgorgement. Specifically, we have found that a smaller mean particle size is inversely related to a greater rate of 1-methylcyclopropene release.

A clathrate of 1-methylcyclopropene with α-cyclodextrin, obtained as a solid particulate product, is modified by comminuting, classifying, or both to obtain a modified particulate. When subjected to identical atmospheric disgorgement conditions of humidity and temperature, identical masses of the modified and unmodified particulates exhibit different rates of 1-methylcyclopropene disgorgement. Specifically, we have found that a smaller mean particle size is inversely related to a greater rate of 1-methylcyclopropene release.

A thermochromic pigment composition including: (A) at least one electron-donor organic dye compound, (B) at least one electron-acceptor compound, and (C) at least one compound corresponding to the following formula (I): in which: X is 0 or a single bond, Z is COO or OCO, R.sub.1 is O-alkyl or (CH.sub.2).sub.mCH.sub.3—R.sub.2 is OCO(CH.sub.2).sub.nCH.sub.3 or H, —y=0-3, —m=12-18; —p=8-18, and on the condition that, when X is 0, y is other than 0. The thermochromic pigment composition are also useable in thermochromic pigment microcapsules ink compositions including the thermochromic pigment microcapsules, and writing instruments including the ink compositions.

A thermochromic pigment composition including: (A) at least one electron-donor organic dye compound, (B) at least one electron-acceptor compound, and (C) at least one compound corresponding to the following formula (I): in which: X is 0 or a single bond, Z is COO or OCO, R.sub.1 is O-alkyl or (CH.sub.2).sub.mCH.sub.3—R.sub.2 is OCO(CH.sub.2).sub.nCH.sub.3 or H, —y=0-3, —m=12-18; —p=8-18, and on the condition that, when X is 0, y is other than 0. The thermochromic pigment composition are also useable in thermochromic pigment microcapsules ink compositions including the thermochromic pigment microcapsules, and writing instruments including the ink compositions.

An ink composition including at least one photochromic pigment or dye, at least one film-forming resin, and at least one solvent in which the at least one photochromic pigment or dye and the at least one film-forming resin are dispersible or dissolvable, wherein the components of the ink composition are present in respective amounts such that the ink composition is in the form of a liquid or gel until evaporation of the at least one solvent, and wherein, upon evaporation of the at least one solvent, the at least one film-forming resin forms a film that (a) inhibits the ink composition from degrading when covered with the sunscreen product or (b) inhibits the ink composition from washing off when the sunscreen is washed off or both, the film-forming resin including shellac, polyurethane, acrylic polymer, silicone polymer or a mixture thereof.

An ink composition including at least one photochromic pigment or dye, at least one film-forming resin, and at least one solvent in which the at least one photochromic pigment or dye and the at least one film-forming resin are dispersible or dissolvable, wherein the components of the ink composition are present in respective amounts such that the ink composition is in the form of a liquid or gel until evaporation of the at least one solvent, and wherein, upon evaporation of the at least one solvent, the at least one film-forming resin forms a film that (a) inhibits the ink composition from degrading when covered with the sunscreen product or (b) inhibits the ink composition from washing off when the sunscreen is washed off or both, the film-forming resin including shellac, polyurethane, acrylic polymer, silicone polymer or a mixture thereof.

An ink composition for a water-based ballpoint pen and a water- based ballpoint pen, which have stable ink flowability even in a so-called fine ballpoint pen, have excellent luster of drawn lines, and do not cause a ball to fall off. The ink composition for a water-based ballpoint pen according to the present invention contains at least an aluminum pigment and 8 to 25 mass% of solid urethane particles with an average particle size of 0.3 to 10 μm. In addition, a water-based ballpoint pen according to the present invention is provided with the ink composition for a water-based ballpoint pen that has the above composition.

An ink composition for a water-based ballpoint pen and a water- based ballpoint pen, which have stable ink flowability even in a so-called fine ballpoint pen, have excellent luster of drawn lines, and do not cause a ball to fall off. The ink composition for a water-based ballpoint pen according to the present invention contains at least an aluminum pigment and 8 to 25 mass% of solid urethane particles with an average particle size of 0.3 to 10 μm. In addition, a water-based ballpoint pen according to the present invention is provided with the ink composition for a water-based ballpoint pen that has the above composition.

An aqueous peelable ink composition substrate comprising: (a) at least one film-forming elastomeric polymer, (b) at least one anionic surfactant, (c) at least one coloring agent, and (d) water, wherein the film-forming elastomeric polymer is acrylonitrile butadiene rubber (NBR) and/or hydrogenated acrylonitrile butadiene rubber (HNBR), and a method for preparing such an aqueous peelable ink composition.