Wikipedia helps:
It can be prepared by boiling calcium hydroxide and sulfur together with a small amount of surfactant. It is normally used as an aqueous solution, which is reddish-yellow in colour and has a distinctive offensive odour.
One recipe for the concentrate is 80 lb. sulfur, 36 lb. pure quicklime, and 50 gallons of water. 2.25:1 is the ratio (by weight) for compounding sulfur and quicklime; this makes the highest proportion of pentasulfide. If hydrated lime is used, an increase by 1/3 or more (to 48 lb. or more) might be used with the 80 lb. of sulfur. If the quicklime is 85%, 90%, or 95% pure, use 38 lb, 40 lb, or 42 lb; if impure hydrated lime is used, similarly increase its quantity. Avoid using lime that is less than 90% pure. Rinse magnesium oxide from the lime and do not keep it in the water; it is a catalyst for hydrogen sulfide gas; sulfur in that form leaves the solution by evaporation, diluting it. Boil for an hour, stirring and adding small amounts of hot water to compensate for evaporation.