Abstract: A process for the preparation of Solid Calcium Bromide Hydrates comprises preparing a highly concentrated Calcium Bromide solution from an initial solution having a lower concentration, bringing it into contact with a cold surface, whereby solid Calcium Bromide hydrates form on said surface, and detaching said solid hydrates from said surface. The concentration of the initial solution is not higher than 60 wt %, typically 52 wt %, and is brought to from 65 to 78 wt %. The said Calcium Hydrates are mainly tetrahydrate Calcium Bromide. The Solid Calcium Hydrates have many uses in the processing of oil wells, for instance preparation of completion fluids, work-over fluids or drill-in fluids in the processing of wells, restoring already used and/or depleted such fluids to the desired, original density. They also have other uses, particularly for soil remediation.