Washing Methods.
—The method of washing with the sulphuric acid is as follows: Into the wooden or lead-lined vat run clear water to the amount of about 10 to 15 per cent of the weight of the grease to be treated, and when the water is in, add one per cent of sulphuric acid to the fat to be washed, the acid to be 66-degree density. It is important that the water be put in first, for if the acid is put into the tank first and the water afterwards run in, an explosion is liable to occur on account of the intense heat generated by the absorption of the water by the acid. In case of an explosion the acid is liable to be thrown on the attendants. After the water and acid have been mixed, add grease, turn on steam and boil until the fat and acid show clear; at first it will be muddy or cloudy. Usually a boiling of twenty to thirty minutes is sufficient. This work should be done on the top floor of the building, or some place where there is ample room for the escape of the vapor, as the fumes of the acid are very strong and are injurious to the building. After the boiling is finished, allow the tank to settle ten to twelve hours, draw off the acid water from the bottom, and if the same is clear and clean it shows that the fat had little foreign substance and the solution can be used over again. If it shows a great deal of foreign matter in the solution it should be run away.
All pipes leading from such treating vats should be of lead. It is also necessary that the pipes in the vats be of perforated lead coils, as iron pipes would very soon be destroyed.
Filtration.
—At times, for bleaching purposes, and especially on low grade greases, it is usual to refine and bleach the oil. The amount of fullers earth to be used in filtering depends upon the condition of the oil to be filtered. With prime steam lard no fullers earth should be used; it is simply filtered through clean press cloths. In the case of lard oils and tallow oils, the color of the oil desired must also determine the amount of fullers earth to be used, no set rule as to the amount to be used in every case being practicable.
Every manufacturer of these different grades of oils has his own grades and standards established, to which the lard refiners usually work, and the amount of bleaching, etc., which is necessary for each individual lot should be governed by the knowledge of the operator, rather than by any set rules.
In the pressing of these articles the oils generally run from 40 to 52 per cent of stock, the balance being stearine, the percentage of oil obtained varying according to the temperature at which it is pressed, and according to the relative market prices for oils and stearines.
CHAPTER XXIV.
SMOKE HOUSE
Smoking Meats — Nomenclature — Soaking — Smoking — Gas Smoking — Temperatures — Treatment After Smoking — Trolley System — Canvased Meats — Shrinkage — Wrapping — White Wash — Dried Beef — Packages — Skipper Fly.