A trip through the Mint
by Harold French
How many readers of The Junior Call have ever been through the mint? Only a very small percentage would be a safe answer, for there are tens of thousands of San Franciscans born who have never visited Uncle Sam’s great coin factory at Fifth and Mission streets.
Although it is open to visitors from 9 to 11:30 and from 1 to 2, the best time for juniors to go through the Mint is early on a Saturday morning. As you enter, the door keeper will politely ask you if you wish to visit the mint, and usher you into a reception room, where you will register your name in a great book and be shown a wonderful collection of rare old coins.
In a few minutes a party of 15 or so are led out by one of the three conductors, who are Grand Army men. One of them, while but a boy of 16, carried a musket on the fields of Antietam, Fredericksburg and Gettysburg. The conductor will advise you to keep together and will load you down a stairway, where for five minutes he will entertain you with the history of a deposit of gold from the time it is received until it is coined.
If you happen to have $50 or, more in sold dust, or as a brick, you will be taken to the receiver of deposits, who weighs your gold and gives you a receipt for the troy ounces it balances. It is then locked in an iron box, and taken to the deposit melter, who melts it in a crucible and pours it into a mold, from which it is emptied in the form of a bar of metal.
This is then sent to the assayers, who finds just how much gold, silver and base metal is in it. Pure gold is worth $20.67 per ounce troy, hence if the assayer reports the gold as being “900, fine,” it means that the deposit contains just 90 percent of the yellow metal, and is worth $18.00 per ounce. The next day, if you are the lucky depositor, you will receive a certificate, on which the cashier will pay you the value of your deposit in bright gold and silver coin, less a few small charges to cover the cost of melting, assaying and refining.
The conductor will then lead you through the boiler room and up an iron stairway, and you will feel as though you were going through the depths of a battleship or a mine. At length you enter the deposit melting room and see the white hot furnaces, heated by gas, where the deposits are being taken out of locked boxes, placed in graphite crucibles, melted and poured into bars. You will not be shown the assaying rooms above, where the values of the deposits aro being determined, nor will you see the re finery where the gold and silver are separated and plated by electric currents on sheets of pure metal.
This fine gold and silver, over 99.9 per cent pure, is sent down to the ingot melting rooms, where it is melted with one-ninth its weight of copper in order to make it tough and wear well. One thousand parts of metal after it is melted into ingots will contain 900 parts of precious metal, as proven by assay.
The coining department
The ingots of gold or silver, which you saw being melted and poured into molds, are taken to the coiner, who reweighs them and delivers them to the operators of the rolling machines. An average gold ingot weighing 72 ounces, and worth $1,300, is a foot in length and half an inch in thickness.
After it has been passed through these powerful rollers it becomes about five feet in length. The ingot is then called a “strip,” which has to be heated to a cherry red for some minutes in order to soften it and render it fit for cutting without cracking. After being annealed in a gas furnace, the strips are cooled in water, dried, coated with beeswax, pointed at one end and pulled through a draw bench by a powerful moving chain. This reduces the thickness of the strips to the exact size whereupon they are fed through cutting presses that punch out the “blanks” at the rate of as high as 360 per minute.
These blanks are carefully washed, dried, and delivered to the adjusters, a number of ladies who weigh each blank, filing off any extra weight and separating any imperfect pieces. The windows in this room are closed to prevent fine gold particles from blowing away, and once every four years, the carpet is burned, the ashes of the last one yielding $9,670.
The blanks are then put through a milling machine at the rate of 10 a second, which by compression raises a ring around the edge of the about to to coin. Once more, the metal is annealed in a red-hot furnace and “whitened” by plunging hot into a tank of dilute sulphuric acid, washed, dried and cleansed in sawdust and then taken to the pressroom for coining.
In this, the last room the visitor enters, powerful coining presses, exerting a pressure of 150 tons, stamp the designs of dies placed above and below the blank. At the instant the impressions are formed on the “head” and “tail” of the blank its milled edge is “reeded” with minute notches and the piece of metal becomes a coin. After passing close inspection, it is placed with others of the same denomination in a stick and is stored in one of the great vaults.
The San Francisco mint has broken several world’s records, among them being the coining of $54,933,520 in double eagles in 33 days. More than $300,000,000 has beon stored in this vast treasure house at one time, while nearly that amount was safe in the building during the great fire.
Though the flames surged savagely around this Gibraltar of granite and sandstone, they found little fuel on which to feed. It was constructed in 1874 as a fire- and earthquake-proof structure, and when, it came to the trial by fire and shock it stood the test.
Old fashioned as it may seem to some, its architecture stands as a type that you may study to your advantage. A firm foundation first of all, then honest construction work from wall to wall; thus was it built to last, and like a pyramid, it did.
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Source publication: The San Francisco Call (San Francisco, California)
Publication date: February 05, 1910