=Co-operative Creameries= were established, taking in 20,000 lbs. of milk and more a day. But in thinly settled sections where the roads were poor it was expensive to haul the milk a long distance to the creamery and _hand separators_ were introduced, each farmer skimming his own milk fresh from the cows and delivering the cream, only, to the creamery. This system has the advantage of leaving the skim milk on the farm in the very best condition for the calves and hogs and of saving time and expenses in transportation. It has the disadvantage that many farmers can hardly be expected to handle all of these separators as skilfully and cleanly as the creamery expert can run his one or few machines, and consequently that the skimming is more or less imperfect—more butter-fat being left in the skim milk and more impurities in the cream than in the whole-milk creamery. But in practice the advantages of the hand separator and cream-gathering system seem to be greater than the disadvantages and it is rapidly taking the place of the whole-milk creameries. _Ripening the Cream._—Butter may be made by churning whole milk, but usually it is made from cream that has been “ripened” or soured by standing for about 10 hours at a temperature of from 65° to 75° F. Modern buttermakers often pasteurize the cream and then add a “starter” to sour it. By preparing the starter with a pure culture of lactic acid bacteria one can get the desired acidity and aroma, and exclude undesirable flavors (as to Pure Cultures and Starters, see under “Bacteria” and “Commercial Buttermilk”). [Illustration: Sanitary Cream Ripener showing coil swung up into cleaning position ] The process of ripening requires considerable skill and attention and is one of the most delicate functions the buttermaker is called upon to perform. In the first place the cream must be faultless, sweet and pure before it is set to ripen, so the buttermaker will have full control of the fermentation. For, if it is already turned or partly fermented, no skill will avail to bring it back to perfection. But with a first class, pure cream the operator has it in his power to turn out perfect butter. In the big western creameries cream is often collected from farms at a distance of a hundred miles or more and in warm weather such cream is likely to arrive at the central plant in more or less advanced condition. It is therefore difficult for the _centralizers_ to make really first-class butter while the “whole-milk creamery” as well as the farmer handling his own milk are in position to control the ripening from the beginning,—starting with pure material and being able to develop the desired flavor and acidity in the cream.