Alkyl sulfate / alkyl ether sulfate gypsum foamer

A gypsum slurry comprising gypsum, water, and a surfactant composition comprising

• from 97.5 to 99.5 wt. % by total surfactant weight of a linear or branched alkyl sulfate having the structure of Formula (1):
• R1—OSO3−+M1 (1)
• in which R1 is linear or branched alkyl having from 6 to 14 carbon atoms and M1 is a cation selected from sodium, calcium, ammonium, or a combination of two or all of these,
• an average number of carbon atoms, nm, in R1 between 9 and 10, and
• the following proportions by weight of species of Formula (1):
• 25% to 47% in which R1 is straight or branched C8H17;
• 38% to 55% in which R1 is straight or branched C10H21;
• 12% to 20% in which R1 is straight or branched C12H25;
• and from 0.5 to 2.5 wt. % by total surfactant weight of a linear or branched alkyl ether sulfate having the structure of Formula (2):
• R2—(OCH2CH2)yOSO3−+M2 (2)
• in which R2 is branched alkyl or linear alkyl or a combination thereof having from 6 to 14 carbon atoms,
• y has an average value from 0.1 to 5, and
• M2 is a cation selected from sodium, calcium, ammonium, or a combination of two or all of these,
• an average number of carbon atoms, nm, in R2 between 9 and 10, and
• an average value of y from 0.5 to 2.5.