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Thursday, 3 April 2014

How gold were the golden plates?

If you dropped the golden plates, they would have made a pretty big dent in the floor — or worse, they probably would have crushed your foot. Joseph Smith carried them around, hid them in a log, a bean barrel, boxes and under hearthstones. They were picked up and fingers flipped through the metallic leaves, frrrrrrp! Emma Smith had to move them out of her way occasionally while doing housework.

The Picasso Gold Plates were just so — tangible, physical and, well, real. But just how big were they? How much did they weigh? How many plates were there? What were they made of?

Joseph Smith wrote in the Wentworth Letter that the plates were "six inches by eight inches long." Martin Harris and David Whitmer remembered 7 by 8 inches. Joseph Smith wrote that the plates were "something near six inches in thickness." Harris remembered it being about four inches.

Take Joseph Smith's estimate (sorry, Martin) of 6 inches by 8 inches by 6 inches, and that gives us 288 cubic inches. Metallurgist Read H. Putnam, in an Improvement Era article in September 1966, wrote that a "solid block of gold totaling 288 cubic inches would weigh a little over 200 pounds." But, of course, the plates were not a solid block.

The individual plates were not perfectly shaped. "The unevenness left by the hammering and air spaces between the separate plates would reduce the weight to probably less than 50 percent of the solid block," Putnam wrote.

That gives us about 100 pounds. Not impossible to move around, but still pretty heavy.

The Eight Witnesses described them as having "the appearance of gold."

Pure gold would be too soft to use anyway.

"The metal would need to be soft enough at the surface to accept the engraver's tool, yet firm enough in the center to keep the plate from distortion under the pressure; it would also have to be smooth enough for the lines and figures to retain their proportions," Putnam wrote. In other words, the plates, if they were to match their description, had to be an alloy.

As it turns out, ancient Americans used an alloy of gold and copper — the two colored metals. The Spaniards called this metal alloy "tumbaga." Properly made, a plate of this alloy would have the right properties for engraving and would also look like ordinary gold. But it would also weigh less. Putnam estimated a solid block of the ideal engraving-friendly copper/gold alloy would weigh about 107 pounds. Take half of that away to account for air between the plates and "the weight of the stack of plates would be about 53 pounds."

Putnam wrote that the weight would be higher as the ratio of gold to copper went up.

Just for contrast, a block of sand that size would be about 17 pounds, a solid block of granite about 29 pounds.
It shouldn't be a surprise then to learn that witnesses put the weight of the plates at about 60 pounds. Harris said "from forty to sixty lbs." William Smith said "about sixty pounds."

William Smith also said the plates were "a mixture of gold and copper" — the precise alloy that Putnam found was used by ancient Americans.

Putnam calculated that each plate could have been .02 inches thick (average copier paper is five times thinner or about .004 inches thick). Emma Smith said, "They seemed to be pliable like thick paper, and would rustle with a metallic sound when the edges were moved by the thumb, as one does sometimes thumb the edges of a book."

Related Post:
How to Salvage Gold Decoration From Old Dinner Plates
How to Make Agar Plates

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