Experiments were carried out on coal fines of two different washeries, at different periods of agglomeration, to determine the size distribution of agglomerates with changes in feed size, pulp density and furnace oil dosage. It is found that the size distribution of the agglomerates follows a self-preserving growth. This behaviour has been generalised using a reduced dimensionless size axis to obtain a characteristic curve. It is shown that this curve is affected only by the nature of the feed and not by the process variables. An equation has been suggested to quantify this characteristic curve of the oil agglomeration process.