Chapter 51 of 57 · 7066 words · ~35 min read

CHAPTER XXIII.

LARD, COMPOUND AND GREASES

HISTORICAL -- QUANTITY AND QUALITY -- NEUTRAL LARD -- KETTLE RENDERED LARD -- PRIME STEAM LARD -- REFINED LARD -- BLEACHING LARD -- FILTER PRESS -- LARD ROLL -- LARD PACKING -- COMPOUND LARD -- COTTONSEED OIL -- REFINING CRUDE OIL -- DEODORIZING COTTONSEED OIL -- PRESSING TEMPERATURES -- LARD OIL -- TREATMENT FOR LARD GREASE.

=Historical.=--The refining of lard in packing houses is comparatively recent, and many people will be surprised to know that even the largest packers only added lard refining to their business within the past twenty-five to thirty years. Previous to that time lard refineries were operated by independent firms, who bought their supply of prime “steam” lard, converting it into the different grades in their own establishments. In the natural evolution of the business this branch was taken up by the packers.

Before the advent of present methods, lard refining consisted in pressing from the lard about 30 to 40 per cent lard oil, sold for lubricating and lighting purposes, etc., and mixing the stearine with straight lard, making a high grade pure lard. At this time the method of bleaching in all lard refineries was accomplished by the use of caustic soda, pearl ash, lime, alum, or other substances, the principal ingredient, being caustic soda. The underlying principle is that alkali, used in proper proportion, saponified the acid in the lard. This process, however, is a thing of the past.

=Quantity and Quality.=--As shown in a previous chapter from thirteen to fifteen percent of the live weight of the hog is fresh lard, consequently where large numbers of hogs are killed the manufacture of lard is an important factor in the packing business. The principal grades are known as neutral lard, kettle rendered lard, prime steam lard, refined lard and compound lard.

Tallow and stearine also enter into the manufacture of refined and compound lards.

=Neutral Lard.=--When oleomargarine was first manufactured it was considered necessary to use natural butter in the mixture in order to give it the proper consistency, as the oleo oil was grainy and coarse, therefore sufficient natural butter was added to change that condition. Some one conceived the idea of using neutral lard made from leaf lard in place of natural butter in oleomargarine. When this was worked out successfully the term oleomargarine practically disappeared and the term “butterine” was substituted. In most of the butterine made today no natural butter is used.

The conditions in making oleo oil and tallows have their parallel in neutral lard and kettle rendered lard. When leaf lard is cooked for kettle rendered lard, if a temperature of from 250° to 260° F. is obtained the tissues of the lard are burned or partially consumed, this heat giving it a flavor which is called “high kettle rendered” flavor. When it is made into neutral this condition is reversed, the lard being melted at a temperature of from 126° to 128° F. At this temperature no burning of tissues is possible, hence the oil extract is neutral in every sense of the word, in color, flavor and smell. With these three essential points the material readily forms the chief substance for butterine by adding milk or cream and oleo oil and cotton seed oil, as desired.

=Manufacture of Neutral.=--The following steps define the process of manufacture necessary to produce neutral:

_Chilling._--The leaves as pulled from the hogs are rapidly sent to a cooling room to be thoroughly chilled. The leaves are spread separately in flat sheets on metal supports, which are preferable to wood. If it is chilled too slowly a strong “hoggy” flavor is developed, which it is impossible to eradicate from the fresh product. The leaf lard should be chilled for twenty-four hours in a temperature of 32° to 34° F.

_Melting._--It is put through a hasher of the Enterprise type to an open top water jacketed kettle, similar in type to an oleo kettle. Frequently the melting kettle is a wooden vat with a galvanized iron kettle inside, the space between the wooden vat and the galvanized kettle being filled with water which is heated to the desired temperature for melting the product. It is not practicable to use a steam jacket as the heat would be excessive and it would be difficult to control. This kettle properly is water jacketed and open top so no pressure is generated.

In a kettle holding 4,000 to 5,000 pounds, water should be warmed in the jacket before lard is put in, the agitator started slowly, not to exceed 10 to 12 revolutions per minute, and the heat should be regulated so as to have the lard all melted and ready to drop in one and one-half hours from the time of starting to hash. By the time the lard is thoroughly melted the temperature should be 126° to 128° F.

_Settling._--As soon as the lard is melted it should be drawn off with a siphon into receiving kettles, which are also jacketed and held at practically the same temperature. When dropped it should be salted with one-half to one per cent of fine salt, letting it stand from fifteen to thirty minutes. In drawing off it should be siphoned through several layers of cheese cloth, forming a strainer, into receiving tanks, where it should settle four hours. It is drawn into tierces through a pipe raised from the bottom to leave one and one-half to two inches of lard in the tank, care being taken that no “bottoms” are drawn into the tierce, as these contain tissues which are, for the most part, undiscernible; also moisture. These ingredients in neutral, being only partially cooked, immediately begin to decompose. It is a delicate article to handle and the settling of all impurities is important. The neutral, when drawn into tierces, should be at a temperature of from 115° to 118° F.

_Storage._--The tierced lard should be kept at a temperature of about 75° F. for about ten or fifteen hours, and then put into a cooler with a temperature of from 45° to 50° F. The tierces should be filled through the bilge and not closed when stored in the first mentioned temperature, the bungs being left out, while the heat is permitted to escape, thus carrying with it considerable flavor, and making the material more neutral than if the tierces were closed as soon as filled.

=No. 2 Neutral Lard.=--This is a neutral lard made from back fat. At times it is profitable to make this product into No. 2 neutral instead of steam lard, for when the market for No. 1 neutral is extremely high there is demand for a good No. 2. When making this, the rind should be skinned off from the back fat, leaving clear back fat to be hashed for neutral. If the rinds are put in, it gives the product a “hoggy” flavor, which makes it undesirable. It is hashed and melted the same as No. 1 neutral, except as to temperature, the melting point for this being 132° to 134° F., method and apparatus as described for the making of No. 1 neutral, being applicable to this.

_Test--Pure Steam Lard vs. Neutral._--Below is a test on raw leaf lard rendered into neutral, showing yield, and percentage of the neutral lard produced; the scrap and bottoms from the kettle being run into kettle rendered lard.

TEST ON LEAF LARD RENDERED INTO NEUTRAL.

Raw leaves 8,958 pounds at $0.08¹⁄₈ per pound = $727.84 Salt for settling 35 pounds at 4.90 per ton = .09 ------- $727.93

_Production:_

Neutral lard 7,880 pounds at $0.09125 per pound = $718.96 Neutral bottoms 1,055 pounds (Run under forty pounds pressure two and one-half hours.) Prime steam lard 497 pounds at 0.082 per pound = 40.75 Tankage 56 pounds at 18.00 per ton = .45 ------- $760.16 ------- Gain on production $ 32.23

Gain per 100 pounds on raw weight, $0.036.

_Percentage Production:_

Neutral lard to raw weight 87.97 Neutral bottoms to raw weight 11.78 Prime steam lard to raw weight 5.55 Tankage to raw weight .63 Prime steam lard to weight of bottoms 47.11 Tankage to weight of bottoms 5.31

Total production of lards 93.52 Total production of raw weights 94.15

_Tanking Leaf Lard:_

Raw leaves 1,000 pounds at $ 0.08125 per pound = $81.25 Prime steam lard 929 pounds at 0.0825 per pound = 76.18 Tankage 5 pounds at 18.00 per ton ------ Loss on production $ 5.07 Loss per pound on raw weight .0051

Prime steam lard to raw weight, per cent, 92.9.

_Test--Chilling and Tanking._--

TEST ON CHILLED LEAF LARD TO DETERMINE VALUE AND YIELD.

Warm leaf lard to cooler 1,000 lbs. Chilled leaf lard 986 lbs. Shrinkage, 1.4 per cent 14 lbs. Weight to test tank, 986 pounds; value per cwt., $7,556. Yield prime steam lard 94.12 per cent; 928 lbs. at $8.025 per cwt. $74.47 Yield tankage (pressed) .81 per cent; 8 lbs. at 9.89 per ton .04 ------ Total $74.51

_Test._--Showing manipulation of 5,000 pounds of back fat to make neutral, kettle rendered lard and pure steamed lard:

TEST ON 5,000 POUNDS OF BACK FAT CONVERTED TO NO. 2 NEUTRAL KETTLE RENDERED LARD AND PRIME STEAM LARD.

Net wt. Per lbs. cent. Back fat 5,000 Less skins removed 586 = 11.72 ----- Skinned back fat rendered to No. 2 neutral 4,414

Production No. 2 neutral 1,846 = 41.82 Bottoms left in kettle 2,568 =====

Bottoms from No. 2 neutral rendered to kettle rendered lard 2,568 Stearine added 270 = 10.51 ----- Total 2,838

Production of kettle rendered lard from above 1,940 = 68.36 ----- Bottoms from No. 2 neutrals 898 Kettle rendered bottoms 673 ----- Loss on production 225 =====

Bottoms from kettle rendered to prime steam lard to tank 673 Production of prime steam lard 307 = 45.62 ----- Skins from back fat rendered to prime steam lard 586 Production of prime steam lard 192 = 32.76

RECAPITULATION.

Net wt. lbs. Rendering back fat 5,000 Oleo stearine added 270 ----- Total 5,270

Production No. 2 neutral lard 1,846 pounds Production kettle rendered lard 1,940 pounds Production prime steam lard 499 pounds 4,285 ------------------- Waste 985

=Kettle Rendered Lard.=--Kettle rendered lard is the purest and best lard made in packing houses and consists of leaf lard and back fat, the proportions varying according to the value of the raw product, usually on a basis of about 60 per cent back fat and 40 per cent leaf. While kettle rendered lard is sold under the label of “pure leaf lard” there is little leaf used, as this part is worth more as a neutral lard than when made into kettle rendered. A very acceptable formula for kettle rendered lard, if handled properly, is as follows:

70 per cent back fat; 15 per cent leaf scraped lard, which is pieces of leaf, scraped out of the hog after the leaf lard has been pulled, and thoroughly chilled; 15 per cent lard stearine.

Where neutral lard and kettle rendered lard are made together a nice flavor may be imparted to the kettle rendered lard by using the bottoms of neutral lard when cooking it, as the scrap from the neutral when brought to the high temperature of kettle rendered lard imparts a rich flavor.

_Process for Kettle Rendered Lard._--The raw product is put through a hasher which cuts the fat tissues, so that when the heat is applied the oil readily separates. The kettle generally used for this purpose is about five feet in diameter and from five to seven feet deep, made of wrought iron, jacketed for steam, with an agitator to keep the product agitated while cooking. The jacket should be kept heated until through hashing, then increased until the temperature of the lard reaches 255° to 260° F., when the pressure should be shut off for one and one-half hours at least--one and one-half hours should be taken to reach this period. If lard stearine is used it should be added at this time, using about 15 per cent for the summer formula. After this period of shut-off, again turn on the steam, holding temperature, allowing the contents to cook until dry, or until no further steam arises, which will consume probably from thirty to forty-five minutes. Stop agitating and add twenty pounds of salt, let stand to settle one hour, then lower into the kettle below, strain through a cloth sieve, the lard being taken off the scrap with a siphon. The scrap will remain in the bottom of the cooking kettle; if handled carefully, very little will pass through the pipe. The lard, when being drawn into the kettle below, should be passed through several thicknesses of cheese cloth in order to catch any small pieces of scrap or tissue.

_Settling._--After the lard is lowered into the settling kettle, allow it to stand two to three hours, then siphon to a third kettle, as considerable scrap will have gone through into the lard from the cooking kettle, strain it through a double thickness of cheese cloth stretched over a frame. In the third kettle a scum will arise on it, which should be immediately skimmed off, and about ten pounds of fine salt added to a 5,000-pound batch, to aid in settling. If convenient, it is advisable to allow the lard to settle in this kettle for twelve hours before drawing it off, although this length of time is not necessary, but a perfect settlement of the impurities is necessary to make the best lard.

_Scrap._--After the lard is drawn from the cooking kettle, the scrap should be drawn from the bottom. This scrap is used in the prime steam lard tank. If, however, there is no other provision for handling the scrap, it should be put into a hoop press (Fig. 150), and pressure applied, thereby liberating all the oil left in the residue, the scrap then being used as “pressed scrap.”

_Packing and Cooling._--Kettle rendered lard is usually sold and used more extensively during the cooler weather. It is very desirable that there should be a light, fluffy top. This is only possible when the lard is drawn hot in a cool room; chilling the lard rapidly causes this appearance at the top, which is always looked upon by the trade as a mark of excellence. When the lard is drawn off into small packages they are placed one on top of the other, covering the top with paper. The cover should not be put on the package until it is chilled, otherwise the fluffy appearance is lost.

[Illustration: FIG. 150.--HOOP PRESS.]

_Drawing Temperatures._--When drawn into wooden packages, such as ten, twenty or fifty pound pails, lard should be drawn at 150° F. If drawn into tins it should be drawn off at 175° to 180° F.; when drawn into tierces, barrels or half barrels it should be drawn at about 130° F. When drawing lard into wooden packages they should be silicated the day before, giving them ample time to dry, as this prevents the packages from soaking up the lard and also prevents excessive shrinkage of the package.

=Refining Prime Steam Lard.=--Refined prime steam lard is made into two products, pure refined lard and lard with beef fat added.

=Pure Refined Lard.=--Pure refined lard consists of prime steam lard with lard stearine added. This is a product resulting when prime steam lard is pressed to obtain lard oil, a process described later; however, the quantity available is quite limited. Descriptions will be confined to the making of lard with beef fat added.

[Illustration: FIG. 151.--SECTION THROUGH TANK FOR MIXING FULLERS EARTH AND LARD.]

=Fullers Earth.=--About thirty years ago the method of refining lard with fullers earth was first inaugurated, and for years only imported earth from England was thought suitable for this purpose. Deposits of fullers earth, of fair quality, have been discovered in the United States and American fullers earth is today used in some lard refineries. Indications are that with improvements in mining and methods of grinding, and possibly also in the discovery of better beds or layers of this substance, manufacturers will not continue to go abroad for supplies of fullers earth.

An explanation of how fullers earth bleaches lard and its kindred fats would be interesting, if anyone knew the exact explanation, but so far there has been no scientific reason given that accounts for this property of this material, therefore no chemical test can be applied to different samples of fullers earth to determine whether they are suitable for refining or not. The only safe test is the practical one of heating a sample together with lard and watching the result of the bleach.

Fullers earth is used for bleaching cotton seed oil and other greases and fats which are subjected to the bleaching process. In improving the color of lard it is done at the expense of flavor, and a wholesome odor, which is natural to the lard, is sacrificed in a greater or lesser degree to the advantage of color. The tendency is to make lard white, even though it loses in odor and taste. In compounding lard this is intensified by the general use of tallow.

[Illustration: FIG. 152.--FULLERS EARTH KETTLE FOR SMALL HOUSES.]

=Bleaching Kettle.=--This can be of a predominant size dependent upon the volume of business. For a moderate business the most suitable dimensions are about six feet in diameter and four feet deep. A sectional view of such a kettle is shown in Fig. 151 and a smaller kettle is illustrated in Fig. 152. It was the practice to use compressed air for agitation so as to mix the fullers earth with the lard. This has been discontinued in the best refineries, as it was found that agitation with air had a tendency to make the lard turn rancid more readily than if agitated by mechanical device.

The kettle is supplied with a vertical shaft, to the bottom of which is attached a propellor about fourteen inches in diameter. Around this is fitted a wire screen about thirty inches high made of galvanized wire, ³⁄₁₆-inch mesh, this screen clearing the blades of the fan about an inch. On top of this screen is fixed an iron pipe approaching to within about eighteen inches of the surface of the lard when the kettle is filled. A kettle of this size will hold about 5,000 pounds of lard for treatment. The agitating blade should revolve at a speed of from 125 to 175 revolutions per minute. This has the effect of producing a miniature whirlpool in the body of lard by driving the lard through the screen against the sides of the kettle, where it rises to the surface and goes down through the funnel-shaped tube to be again driven through the screen. In this way the fullers earth is thoroughly mixed in and if there is a tendency to “lump” the lumps are readily broken up by impact.

=Bleaching Lard.=--If cold lard is used it should be melted and any sediment or moisture which settles should be drawn off. It is best not to draw off too close to the bottom so as to avoid any moisture.

The temperature at which lard should be bleached is an important matter to be determined. If the lard has been heavily cooked and has a strong steam flavor, a temperature of 180° F. is correct. If the lard has not been well cooked a somewhat lower temperature is necessary. As a rule the lower the temperature at which bleaching is done, the more fullers earth is required to get the proper bleach and at the same time as little earth flavor as possible is a point for careful and intelligent consideration. The best way to determine, where there are large quantities of lard, is to take a small sample and make tests in the laboratory. The point to be obtained is to get the bleach with as little of the flavor of the earth as possible. Generally speaking, from three-fourths to one and one-half per cent of fullers earth will get the desired result.

When the lard is brought to the proper temperature, fullers earth is put in the kettle, when it is agitated from eight to twelve minutes, then pumped through the filter press as rapidly as possible. It takes a certain length of time for fullers earth to do its work properly, and a strong agitation of from eight to twelve minutes appears to be the best method to adopt in order to obtain the full effect of the earth.

=Refining Tallow Separately.=--Where tallow is used in lard, it is always advisable to bleach the tallow separately. This is done in the same manner as described for lard, with the exception that about three per cent of fullers earth is used, after which it is pumped through the filter press and into the receiving tanks.

[Illustration: FIG. 153.--FILTER PRESS.]

When it is compounded with the lard, the desired amount should be put into the kettle with the lard after it is treated. The same is true of oleo-stearine, except that in the bleaching of this article from one-half to one and one-half per cent of fuller earth is sufficient. Measures must be taken to see that ingredients are intimately mixed before passing the product to the rolls.

The use of tallow or stearine is for the purpose of cheapening the product, as well as hardening it, the formula for same being made according to the values and conditions under which the lard is to be sold. For instance lard going south, or into a warm climate, is made much harder than lard for a temperate climate; hence lard formulas, generally speaking, are worthless for general use, the different formulas being made to suit widely different conditions, and their availability also depends to a considerable extent upon the fluctuation of values.

=Filter Press.=--After the contents of the kettle have been pumped through the filter air pressure should be turned into the filter press in order to blow out all the lard possible. After this live steam should be turned on, expelling the balance of the lard from the pipe. A large portion of this latter lard, however, is unfit to be used again, as it contains sediment and fullers earth combined, having a rank, strong odor, and can be used only for grease.

[Illustration: FIG. 154.--LARD COOLING CYLINDER.]

=Lard Roll.=--This is a device provided for cooling lard in a film so as to bring plenty of air in contact with the surface during the congealing. After the lard has been put through the filtering press it goes to a receiving tank and is next passed over rollers for chilling. (Fig. 154.) These are cast iron cylinders containing refrigerated brine. The cylinders revolve at from ten to fourteen revolutions per minute, the lard being congealed on the outer surface. Fixed against the side of the cylinder is the edge of a steel knife which scrapes close to its surface. The lard, in contact with the cool surface of the cylinders, congeals and as it passes to the knife it is removed and drops into the trough. Here it is thoroughly beaten by a revolving shaft with pickers on it, so that all lumps are broken and the grain is of a smooth, even consistency. Pure lard passes to an agitator, which is a jacketed kettle, where it is given a thorough agitation and drawn off cool as possible, the object being to have the different ingredients thoroughly mixed at a low temperature.

At times rolls are used in tandem. When a bountiful supply of cold water, say at 60° F., is available, the saving in refrigeration justifies the use of tandem rolls. In this instance the first roll is elevated so as to gravitate the lard to the feed of the second.

WEIGHT OF LARD PACKAGES.

=Lard Packing.=--Refined lard is not usually drawn in a cooler. In most climates the non-refrigerated rooms will suffice. It is packed in tubs, barrels or tierces of wood. The lard, when available, in the picker trough, is usually chilled and stiff. The use of a pump is made to withdraw and force it through a strainer in an enlarged section of the pipe, so as to effectually break all lumps. A relief valve should be placed on the line to spill into the picker in case the draw cocks are all suddenly closed.

=Lard Packages.=--In wooden packages tare is deducted. The table on preceding page shows the actual weight of the different packages which are usually made from an X L grade of tin. Inasmuch as lard sells at more per pound than the tin costs, there is always an endeavor to get the packages as heavy as consistent.

=Country Style Lard.=--Many moderate sized plants that do not cater to a trade accustomed to highly refined lard, prefer to make kettle rendered lard as most of their output, using leaf, back fat and trimmings, adding the complimentary proportion of killing lard and agitating the whole in a water jacketed agitator. All implements used are similar to those described previously, also the method of drawing from the agitator to packages is the same. Beef fat can be rendered in the same way when oleo departments are not operated, and it can thus be used to good advantage.

=Compound--What it is.=--Compound is a substitute for lard and is made of cotton seed oil and oleo stearine, or tallow, or both. The formula on this article varies according to the relative values of the ingredients. The generally accepted formula is 80 per cent cotton seed oil, and 20 per cent oleo stearine.

If the market price of oleo stearine is high, a formula may be substituted as follows: 75 per cent cotton seed oil, 7¹⁄₂ percent tallow, 17¹⁄₂ per cent oleo stearine. In cold weather even a smaller amount of stearine may be used and a proportionately larger amount of tallow.

=Cottonseed Oil.=--This is a product derived from cotton seed. Before the manufacture of cotton seed oil, the cotton seed, removed from the cotton, was thrown in large compost heaps and after decomposition, was used sparingly as a fertilizer. An idea of its value may be gained from the following table. From one ton of seed, by average, is obtained:

270 pounds or 36 gallons of oil at 28c per gallon $10.08 750 pounds cotton seed meal at 90c per 100 pounds 6.75 850 pounds hulls at 15c per 100 pounds 1.27 30 pounds lint at 3¹⁄₂c 1.05 ------ Total value $19.15

100 pounds waste and dirt.

The oil when extracted from the seed is termed “crude oil.” In refining this oil the loss varies from 7 per cent to 12 per cent, on an average about 9¹⁄₄ per cent.

=Refining Crude Oil.=--The crude oil is purchased by refiners and treated to produce “yellow oil.” In this process it is put into a tank (it is generally considered profitable to refine cotton seed oil only in large quantities) supplied with a revolving agitator. Into the tank is put a solution of eighteen to twenty per cent caustic soda. The quantity and strength of the solution necessary is determined by treating a small sample. To a small sample of oil add the soda solution, stirring continuously, having it heated to a temperature of 160° to 180° F. When sufficient soda lye has been added a floculent precipitation will be noticed. This indicates a “breaking” of the oil. By calculation of the relative amount the comparative quantities can be arrived at.

An excessive amount of lye will saponify its equivalent in good oil, therefore care must be exercised to see that only the proper amount is used. In a practical way the soda is introduced in the crude oil solution and agitation is started to insure the thorough mixing of the caustic soda and the oil. The floculent substance appearing, the agitation is stopped and the oil allowed to settle, the sediment and substance other than oil collecting at the bottom of the tank. A small quantity (about one-quarter of one per cent by weight) of fullers earth is added and the oil removed by pumping through a filter press producing what is known to the trade as “yellow oil.”

The sediment, known as “foots” is collected in kettles and treated with additional lye, boiled and settled with salt; water added, settled and drawn. This treatment is duplicated as many times as necessary, until the soap stock will separate from impurities. When thoroughly settled draw the soap stock into packages for the soap trade. The finished “foots” contains about 33 to 40 per cent of moisture and a small percentage of lye.

=Deodorizing Cotton Seed Oil.=--The “yellow oil” of trade has a decided flavor which it is desirable to remove, and this process is accomplished by deodorizing. (See Fig. 155.)

_Treating Tank._--This tank is equipped for heating the oil to a very high temperature by the introduction of a large coil surface, preferably rings, one within the other and arranged so that each ring is accessible. The kettle coils, etc., should be made extra heavy. The top of the kettle must also be hooded and as the oil boils violently the steam must be given free opportunity to escape. The escape pipe should be at least sixteen to twenty inches in diameter in a tank six feet in diameter, and should be provided with a goose neck, so that the steam rising which condenses, does not drip back into the tank. Fig. 155 show the construction of an oil treating tank.

The exhaust pipe extends into the atmosphere a short distance above the deodorizing tanks. On account of the extreme agitation caused by the heat, the oil is likely to boil over and waste. Special attention is called to the crook or neck in the exhaust pipe with two-inch outlet at the lowest point. This is done so that the condensation will not run back into the oil, but can be taken out at this point.

=Process For Oil.=--The tank is filled with oil to about half its capacity. The oil is then heated to a temperature of 320° to 360° F. After being held at this temperature for an hour to an hour and a half, it is ready for the washing process. This is done by means of a two-inch perforated pipe at the top of the kettle, through which is sprinkled cold water on the oil. The extreme temperature evaporates the water very rapidly and at the same time causes a precipitation. The water should be allowed to run for five minutes, and then the body of oil should stand for from one to two hours. The cone, or bottom of the kettle, will be found to have a sediment which has been precipitated from the oil. This “bottom” should be drawn off, and the steam again turned on the coils.

[Illustration: FIG. 155.--DEODORIZING TANK FOR COTTON SEED OILS.]

_Blowing._--The oil is heated to the original temperature and steam of high pressure and temperature introduced into the body of the oil. The length of time required for treating the oil depends largely upon its nature, some oils being more neutral and more nearly odorless than others, consequently no exact rule can be laid down that would fit all cases; it must be left to the judgment of the person handling the oil.

_Pressure and Temperature._--To obtain the temperature above mentioned a pressure of 150 pounds should be carried, and late practice introduces a superheater for reheating the steam to insure high temperature by adding 100° to 150° F. to the steam temperature.

[Illustration: FIG. 156.--SECTION OF BOTTOM OF DEODORIZING TANK.]

_Bleaching Process._--As soon as the oil is deodorized it is drawn off and allowed to cool. It is pumped into the treating kettle, or what is known in refineries as the “dirt” kettle. There it is brought up to a temperature of 160° F., when the fullers earth is added, generally using from one to two percent of earth with this bleach, following an agitation of about ten minutes. It should then be pumped through the filter press into the receiving tank, where it is held until used. After going through this process the oil is known to the trade as “water white.”

[Illustration: FIG. 157.--SECTION THROUGH EXHAUST HOOD OF DEODORIZING TANK.]

_Mixing._--Refined tallow or oleo stearine melted and clarified by pumping through a filter press without the use of fullers earth is added to the cotton seed oil so prepared, and the mixed substance, containing proportions previously described, are ready for passing over the cooling roll.

_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.

=Pressing Temperatures.=--The usual pressing temperatures for the several kinds of commodities pressed are as follows:

Tallow 58° to 65° F. Prime steam lard 48° to 50° F. Neatsfoot oil 45° to 48° F.

These and the temperature of the room, however, are subject to variations.

=No. 2 Lard Oil.=--A lower quality of lard oil is made from hog greases. These are made from condemned hogs, catch basin skimmings and similar sources. The methods are similar to those used for No. 1 lard oil, except that the former is treated as an edible product and the latter as inedible.

The extracted stearine is sold or used for soap purposes.

=Cold Test-Oil.=--It is not customary to speak of any particular cold test of cotton or grease oils; however, in case of pure lard oil, pressed, it would have a cold test of about 42° F. Pure neatsfoot would have a cold test of about 45° F. In case colder degree oils are desired, either pure lard or neatsfoot, it would be necessary to make the lard colder than above; as to neatsfoot oil, if it is desired to make a 30° F. test, it would be best to make two pressings. First chill stock to a temperature of 42° F., pressing it in a room at 45° F. and then take the oil that is made in this way, refrigerating it in a room at 32° F. and pressing it at a temperature of 32° F.

=Treatment for Lard Grease.=--Before pressing the low grade greases it is necessary to wash with sulphuric acid to eliminate the impurities, such as water, lime soaps, albuminous matters and ordinary dirt. Shallow wooden vats are ordinarily used for this purpose, the vats being of greater width than depth, as the acid water settles best in a shallow receptacle. Where a comparatively small amount of work is to be done an ordinary wooden vat made out of good sound pine, with three-inch staves and well bolted together, is all that is necessary, but where the work is continuous these wooden vats should be lined with ten-ounce lead, as the acid very soon destroys the vats.

_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.