Abstract: The method for automatically regenerating molding sands consists in mixing the spent sand and in intermittently withdrawing a cylindrical test sample of sand. The compactibility of the test sample is measured intermittently by determining the reduction in height of the sample under the action of a predetermined force. The quantity of water to be added to the sand is determined by means of a microprocessor from the result of the measurement and from the temperature of the sample. The results of measurements of compactibility and compressive strength of the test sample are transmitted to the microprocessor which determines the quantity of bentonite, of foundry black and the like to be added to the spent sand.