Abstract: A water-based ink includes: a dye; water; an acidic preservative; and at least one of a surfactant and a penetrant. The acidic preservative preferably includes at least one selected from the group consisting of a polyvalent unsaturated fatty acid, a polyvalent unsaturated fatty acid salt, dehydroacetic acid, and a dehydroacetate. A content of the acidic preservative in the water-based ink is preferably 0.3% by mass to 6.0% by mass relative to a total mass of the water-based ink. The surfactant preferably includes an acetylene-based surfactant. The penetrant preferably includes at least one selected from the group consisting of an alkylene diol and a glycol ether compound.

Abstract: A water-based ink includes water, a colorant, and a water-soluble organic solvent. The water-soluble organic solvent includes a penetrating agent and a wetting agent. The penetrating agent includes a compound of formula (1), and the wetting agent comprises a compound of formula (2). In formula (1), x is 4 or more, and y is 2 or more, in formula (2), x is 2 or more. An amount of the compound of formula (1) relative to a total mass of the water-based ink is preferably 0.1 to 2.0 mass %. An amount of the compound of formula (2) relative to a total mass of the water-based ink is preferably 1.0 to 10.0 mass %.

Abstract: A water-based ink includes a colorant, water, a penetrating agent, and a wetting agent. The penetrating agent includes diethylene glycol monohexyl ether (DEHE). The wetting agent includes a compound having an SP value of 12 to 14. A ratio (A/B) of an amount (A) of the compound having an SP value of 12 to 14 to the amount (B) of DEHE is 2.5 or more. The wetting agent preferably includes at least one of triethylene glycol and tripropylene glycol. The ratio (A/B) of the amount (A) of the compound having an SP value of 12 to 14 to the amount (B) of DEHE is preferably 2.5 or more and less than 10.

Abstract: A water-based ink includes a pigment, water, a penetrating agent, and a binder resin. The penetrating agent includes a compound of formula (1). x is greater than or equal to 6. The binder resin includes a urethane bond. A content of the binder resin in the water-based ink is greater than 1.0 mass %. The compound of formula (1) is preferably diethylene glycol monohexyl ether. The water-based ink preferably further includes an organic solvent having a solubility parameter (SP) value of 12 to 14.

Abstract: A water-based ink for inkjet recording, includes: a pigment; water; and an acidic preservative. The pigment is preferably a self-dispersing pigment. The acidic preservative preferably includes at least one selected from the group consisting of a polyvalent unsaturated fatty acid, a polyvalent unsaturated fatty acid salt, dehydroacetic acid, and a dehydroacetate. A content of the acidic preservative in the water-based ink is preferably 0.5% by mass to 5.0% by mass relative to a total mass of the water-based ink. The water-based ink preferably further includes a surfactant. The water-based ink preferably further includes a penetrant which includes at least one selected from the group consisting of 1,2-hexanediol, 3-methyl-1,5-pentanediol, and triethylene glycol-n-butyl ether (BTG).