of at least one additive and calcium sulphate is added to the cellulose fibre solution this process includes the following stages 1 preparation of a suspension according to the invention as described above 2 preparation of a cellulose fibre suspension in water 3 addition of the suspension according to the invention to the cellulose fibre suspension in the paper circuit in a paper making process using an aqueous suspension according to this invention this calcium sulphate and at least one of these additives is kept under suspension by stirring until the time the cellulose paste is added the stirring time depends on the kind of calcium sulphate used and the kind of additive s and is in general equal to or greater than 30 minutes as an advantage the paper making process according to this invention allows highly opaque paper to be obtained at a low cost the batch calcium sulphate used specifically in the following tests is caso 4 x0 3 h 2 o i e n 0 3 moles when this calcium sulphate is added along with at least one additive in water to create an aqueous suspension according to this invention this compound is hydrated to a greater or lesser extent depending on the value of n in the tests described below a stirring speed of 3000 rpm and a stirring time of 30 minutes were used with calcium sulphate hydrated with n 0 3 90 of saturated caso 4 water 10 of caso 4 2 h 2 o 90 of saturated caso 4 water 8 2 of caso 4 0 3h 2 o 1 8 h 2 o 91 8 of saturated caso.