The kettles should be close to the boiler room, and the steam pipes feeding them should be as straight and short as possible, and covered with magnesia pipe covering to prevent excessive loss of heat by radiation. It is not an uncommon sight in canning plants to see the main pipe from the boiler to the cooking kettles pass through an areaway between two buildings, and have no protective covering whatever. Such sights, however, are becoming more infrequent, as packers are plugging up many of the leaks through which dollars have escaped every day in years gone by. The condensation from the steam traps can, of course, be used right over again in the boilers. Copper-Jacketed Kettles Copper-jacketed kettles used for condensing tomato products range all the way from 50 gallons capacity to 500 gallons, the larger size making a batch of finished pulp of about 250 gallons as a rule. A larger batch than this can be cooked in a 500–gallon kettle, but it is not advisable to keep pumping fresh tomato juice into the kettle too long, as it gives too long a cook to the first that goes in. Forty-five minutes should be the absolute limit for a batch of pulp, no matter what kind of a kettle it is cooked in, and it is much better to confine the cooking time to 30 minutes or less. The shorter the cook, the better the color and flavor of the finished product, other things being equal. Tinning Kettles Copper kettles are frequently lined with block tin to prevent the acid of the tomato from dissolving some of the copper. The desirability of this is argued both from a standpoint of health and flavor, as dissolved copper, even in small quantity, has a very bitter taste. It should be remembered, however, that the acid of the tomato, which is generally thought to be citric acid, is a weak organic acid, and the amount of copper dissolved in a batch cooked not over an hour is exceedingly small; certainly so small as to have no ill effect upon health. As to the question of flavor, it would indeed take a very delicate palate to detect among a half dozen samples which ones were cooked in an unlined copper kettle, and which in a kettle lined with block tin or silver. The latter is said to be used by some packers.