_Filter Press._--The filter press (Fig. 158) should not be used more than two or three times until it is taken apart, all the sediment and dirt removed and clean cloths substituted. Continued use of filter cloths, without proper cleaning, has a deteriorating effect upon the material pumped through the presses, and different kinds of products should not be passed through the same press. _Color and Roll Treatment._--Color is an important feature of compound, when an odorless oil has been produced. The mixture passed to the rolls is usually at a temperature of 120° F. and this heated body of material amounting to 4000 pounds per hour on an eight foot roll requires a very large capacity of refrigerating equipment. It is desirable to maintain a brine temperature in the shell of from zero to five degrees above. A fifty-ton refrigerating equipment of commercial rating is inadequate for this duty. Consequently compound manufacturers must have ample refrigerating machine capacity. The lard roll is preferably of the size noted and should operate at not to exceed seven revolutions per minute, provided brine of the above temperature is supplied; fewer revolutions if temperature is higher, which naturally reduces the capacity. The lard roll, pump, and strainer equipment is the same as described for lard, except that the lard is packed directly from the picker trough without the use of an additional agitator. =Hydrogenation of Oils.=--A new process has been devised whereby soft oils, such as cotton seed oil, can be hardened so as to make a purer vegetable product. The substance has quite a large field but it is not intimately connected with the packing business. =Cotton Seed Stearine.=--This is a purchasable product and is used at times as a substitute for oleo stearine. =Lard Oil.=--The production of lard oil used in compounding lubricating oils and illuminating oils is still carried on to some extent. The process consists of graining the oils in graining tanks or in seeding trucks similar to oleo oil graining trucks. _Pressing._--The lard cooled to a temperature of 40° F. is placed in cloth wrapper arranged so that all oil is strained through the wrapper. The solid substance contained in the wrapper is lard stearine used to harden pure lard. [Illustration: FIG. 158.--FILTER PRESS FOR LARD OR OLEO OIL.] _Graining._--After the fats have been washed they should be drawn into trucks or tierces and placed in a room where there is good ventilation, and kept there for about two days, giving the acid fumes an opportunity to pass off; the fat will then be found to be lowered to about 80° F. and should then be removed to a room that is refrigerated. After remaining in this temperature three or four days the fats will be found to be crystallized, or grained, and of about the temperature of the rooms. It is then ready to go to press.