The pigment was originally prepared by making a solution of sodium carbonate at a temperature of around 90 °C (194 °F), then slowly adding arsenious oxide, while constantly stirring until everything had dissolved. This produced a sodium arsenite solution. Added to a copper sulfate solution, it produced a green precipitate of effectively insoluble copper arsenite. After filtration the product was dried at about 43 °C (109 °F). To enhance the color, the salt was subsequently heated to 60–70 °C (140–158 °F). The intensity of the color depends on the copper : arsenic ratio, which in turn was affected by the ratio of the starting materials, as well as the temperature.
It has been found that Scheele's green was composed of a variety of different compounds, including copper metaarsenite (CuO·As2O3), copper arsenite salt (CuHAsO3 and Cu(AsO3)2·3H2O)), neutral copper orthoarsenite (3CuO·As2O3·2H2O), copper arsenate (CuAsO2 and Cu(AsO2)2), and copper diarsenite (2CuO·As2O3·2H2O).