Now that we have followed through the process of making the white-lead powder, or pigment, let us take a little time to study the preparation of the other white powder, known to the paint trade as “oxide of zinc.” This is prepared in a manner quite different from that of the white lead. First the ore which is mined from the earth containing the metallic zinc is carefully selected by expert workmen and placed in a special kind of furnace, being mixed with hard coal, such as we use in our heating stoves.] [Illustration: A ZINC SMELTER--THE MEN KEEP THEIR MOUTHS COVERED SO AS NOT TO INHALE THE VAPOR, WHICH IS POISONOUS The burning of the coal causes an intensely high temperature, sometimes being several thousand degrees. This causes the zinc ore to be consumed as it were or to pass into a form of vapor. This vapor is carried through huge pipes which are several feet in diameter and extend for a long distance. While these vapors are passing through these pipes it becomes cooled. After becoming cooled it takes on the form of very fine white powder, coming from the pipes in much the same way that snow falls from the sky in the winter. This is collected and placed in barrels, after which it is ready for the paint-maker without further preparation.] ~WHERE LINSEED OIL COMES FROM~ Since we have followed the preparation of the two important white pigments used in making our can of paint, it is now important that we devote a little thought to the liquid which is to be used. This is called “Linseed Oil.” Linseed oil is of a golden yellow color, resembling the appearance of thin syrup which we sometimes have on the table. This oil is taken from the seed of the flax plant. It might better be called “Flaxseed Oil,” yet it is not commonly known by that name, but is nearly always referred to as “Linseed Oil.” Flax is grown in many parts of the world, the most important places being the United States of America, Dominion of Canada, Ireland, India and the Argentine Republic. In the United States, the seed is sown early in spring, much the same as is done with other crops, and ripens and is harvested early in the fall of the year. The harvesting and separation of the seed from the plant or straw is done very much in the same way that other crops, such as wheat and oats, are harvested. The seed is then taken to market and is ready for the extraction of the oil, which is done by men who are known as “oil crushers.” [Illustration: PRESSING OIL OUT OF FLAXSEED.] [Illustration: REMOVING OIL CAKE FROM PRESS.] The oil is extracted from the seed by a very simple process. Usually the seeds are heated by steaming them, after which they pass through a mill, being ground to a coarse mass, which is then placed in very powerful machines called “Hydraulic Oil Presses,” which squeeze the oil from the seed, leaving the remainder in the form of large cakes which are then ground to a mealy-like powder which is used as food for cattle and is very much prized.