This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
Hot percolation is impracticable. Any percolate which is obtained by heated liquids is over-saturated, and necessarily deposits on cooling such matters as it cannot retain in solution, and with every fresh deposition the solvent power of the remaining solution becomes altered, so that in many cases the precipitation continues, though perhaps very gradually, even though the product may be filtered clear from time to time. "A percolate that has been obtained clear at a temperature as low or lower than any to which it is exposed afterwards, usually remains clear, if care is taken that the menstruum is not altered by evaporation or dilution afterwards. However, a reservation might be made in favor of the hot process percolator in certain cases. When the constituents of a drug which is to be exhausted, are more of a resinous than gummy nature, and when the menstruum to be used is strong alcohol, the use of such a percolator will be an advantage, provided it permits the avoidance of loss of alcohol by evaporation". - American Druggist. As all extracts employed in the manufacture of saccharine beverage, are used with water, and therefore must be water-soluble -that is, dissolve entirely in water without causing any separation or turbidity, the extracts prepared by the hot percolating process are not suitable, and this process should not at all be employed by carbonators. The cold process with diluted alcoholic menstruum is recommended.