Disclosed is a sol-gel imprinting ink composition comprising a sol and an additive for promoting gelation of the composition during imprinting at an imprinting temperature. The composition has a pH of 4-7 when mixed with an equal volume of deionized water and measured at 20° C. and 1 atm. The additive is the reversible reaction product of a protic acid and a proton-accepting base. The vapour pressure of the acid is higher than that of the base at the imprinting temperature such that the concentration of the base in the composition increases relative to the concentration of the acid in the composition during imprinting, resulting in basification of the composition. Further disclosed is a method of forming a patterned layer with such a sol-gel imprinting ink composition, and an optical element and an etch mask respectively including the patterned layer.