A method of reducing water in a gypsum slurry with the water to stucco ratio from 0,1 to 0,9, based on dry weight of the stucco, comprising: preparing a gypsum slurry by mixing in a mixer a mixture comprising water, calcined gypsum, a defoamer and a dispersant, wherein the dispersant consists essentially of a first and a second repeating unit, wherein said first repeating unit is an olefinic unsaturated mono-carboxylic acid repeating unit or an ester or salt thereof, or an olefinic unsaturated sulphuric acid repeating unit or a salt thereof, and said second repeating unit is of the general formula where R 1 is represented by and wherein R 2 is hydrogen or an aliphatic C 1 to C 5 hydrocarbon group, R 3 is a non-substituted or substituted aryl group and preferably phenyl, and R 4 is hydrogen or an aliphatic C 1 to C 20 hydrocarbon group, a cycloaliphatic C 5 to C 8 hydrocarbon group, a substituted C 6 to C 14 aryl group or a group conforming to the formula wherein R 5 and R 7, independently of each other, represent an alkyl, aryl, aralkyl or alkylaryl group and R 6 is a divalent alkyl, aryl, aralkyl or alkaryl group, p is 0, 1, 2, 3, inclusive, m and n are, independently, an integer from 2, 3, 4, 5, inclusive; x and y are, independently, integers from 1 to 350, inclusive and z is from 0 to 200, inclusive; adding a first portion of retarder to the slurry into the mixer during mixing, the first portion being added in the amount from 0,488 g/m 2 to 4,88 g/m 2 (0.1 Ib/MSF to 1 Ib/MSF), sufficient to prevent a buildup of gypsum crystals within the mixer; adding a second portion of retarder to the slurry after the slurry has been mixed, the second portion being added in the amount from 0,244 g/m 2 to 2,44 g/m 2 (0.05 Ib/MSF to 0.5 Ib/MSF) or from 2,44 g/m 2 to 4,88 g/m 2 (0.5 Ib/MSF to 1 Ib/MSF), sufficient to improve the fluidity of the slurry. preparing a gypsum slurry by mixing in a mixer a mixture comprising water, calcined gypsum, a defoamer and a dispersant, wherein the dispersant consists essentially of a first and a second repeating unit, wherein said first repeating unit is an olefinic unsaturated mono-carboxylic acid repeating unit or an ester or salt thereof, or an olefinic unsaturated sulphuric acid repeating unit or a salt thereof, and said second repeating unit is of the general formula where R 1 is represented by and wherein R 2 is hydrogen or an aliphatic C 1 to C 5 hydrocarbon group, R 3 is a non-substituted or substituted aryl group and preferably phenyl, and R 4 is hydrogen or an aliphatic C 1 to C 20 hydrocarbon group, a cycloaliphatic C 5 to C 8 hydrocarbon group, a substituted C 6 to C 14 aryl group or a group conforming to the formula wherein R 5 and R 7, independently of each other, represent an alkyl, aryl, aralkyl or alkylaryl group and R 6 is a divalent alkyl, aryl, aralkyl or alkaryl group, p is 0, 1, 2, 3, inclusive, m and n are, independently, an integer from 2, 3, 4, 5, inclusive; x and y are, independently, integers from 1 to 350, inclusive and z is from 0 to 200, inclusive; adding a first portion of retarder to the slurry into the mixer during mixing, the first portion being added in the amount from 0,488 g/m 2 to 4,88 g/m 2 (0.1 Ib/MSF to 1 Ib/MSF), sufficient to prevent a buildup of gypsum crystals within the mixer; adding a second portion of retarder to the slurry after the slurry has been mixed, the second portion being added in the amount from 0,244 g/m 2 to 2,44 g/m 2 (0.05 Ib/MSF to 0.5 Ib/MSF) or from 2,44 g/m 2 to 4,88 g/m 2 (0.5 Ib/MSF to 1 Ib/MSF), sufficient to improve the fluidity of the slurry.