—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.