How to Tell Copper, Brass and Bronze Apart Without a Laboratory

Every scrap peddler on the Dover road swears his metal is pure copper, the way every bridegroom swears he was a choirboy. The distiller who builds his own apparatus should believe neither one. To catch a liar in metal he needs only his eyes and ears, a good file, a fire, and a suspicious nature. Here is how we go about it at Fort Wilkins on the Suncook Valley Turnpike.

Three Cousins of One Red Family

Three cousins figure in this inquiry. Copper is the patriarch: soft, red, honest and easy to bend, like a good grandmother. Brass is copper that married zinc. It went yellow and showy and likes to pass itself off as gold. Bronze is copper that married tin. It went brown and hard and joined the army.

No New Hampshire man digs copper out of his own back pasture. Paul Revere, the midnight rider himself, gave up riding for rolling. In 1801 he opened the first copper-rolling mill in America at Canton, Massachusetts, and he rolled the sheathing for the frigate Constitution, so Old Ironsides is truly Old Copper-Bottom. Vermont ore from the Elizabeth Mine at Strafford and the Ely works at Vershire comes down the Connecticut and up our turnpike by wagon. Since the forties the Lake Superior country has been digging native copper pure enough to hammer straight out of the ground.

This war has driven the price up hard. Every cannon foundry in the Union wants copper for bronze, and every cartridge works wants it for brass. So the scrap trade has gone wild, and half of what is sold as copper sheathing is nothing of the kind. It is Muntz metal, a brass of about sixty parts copper to forty of zinc, patented in 1832 by George Muntz of Birmingham. It looks like copper in bad light to a man who is drunk.

The Pinchbeck Peddler and the Deputy's Kettle

Pinchbeck is the cheap brass a London clockmaker of that name made up to look like gold, and the word has meant 'fake' ever since. Two Augusts ago a Pinchbeck fellow came up from Dover in a checked waistcoat. He swore by his mother's grave that his wagonload of sheathing was pure Revere copper, twelve dollars the lot. Three strokes of my file brought it up yellow as a canary's backside. He called me a tooth-yanking backwoods quack, snatched back his sheet, and stepped right over the chain of Barnaby, my black bear.

Barnaby does not hold with fraud, and he holds even less with men who cross his supper path. His first bite took the coattails. His second took the trousers and a good strip of what they guarded. The peddler hit a high C no Concord soprano ever reached and went over the stone wall without touching it. I caught him by the Suncook bridge and closed his seat with harness thread and a sail needle. He came for twelve dollars and left with eleven stitches. I kept the sheathing, which makes fine yellow hinges, and hinges are all brass is good for around a still.

Metal has fooled the law too. On my first arrest a deputy hauled my old brass hog-feed kettle to Concord, declaring it the still. All the while the real copper lay under a cord of maple in the woodshed. The magistrate asked him whether he had ever seen a still. Not before that day, said the deputy, and it turned out he still had not.

A Carolina Runner's Hard Lessons

Junior Vance hauled loads out of the Brushy Mountains of North Carolina faster than any man there, and he learned his metals from the hard end. A fellow near Moravian Falls sold him a pot black with soot. The second batch came off it with a greenish cast, and the man who bought a jar spent the night hugging a fencepost. That was white vitriol, which is zinc. Doctors give it to make a patient vomit. Junior scratched under the soot with his pocketknife and found every bottom patch yellow as a buttercup: brass, soldered in where the copper had burnt through. He took a sledge to the pot and then sold the seller a mule, blind in one eye and mean in both.

Later, thieves peddled the pieces of a cracked Baptist bell from near Traphill as copper at a dollar a pound. Junior knocked a chunk against a creek rock and it sang like Sunday morning. 'Copper don't ring like that,' he told me. 'Copper goes thunk, like a sack of meal.' When he bent it over a stump it snapped clean in two. He bought back every piece he could and returned them to the deacon, and the bell was recast.

Another night, a polished brass petcock flashed in a revenue agent's lantern while Junior lay in the laurel twenty feet off. By luck a possum walked out just then and took the blame. Next morning Junior blacked every brass fitting he owned with stove polish. 'Copper turns brown on its own,' he says. 'Brass stays shiny out of pure vanity.'

Five Tests at the Anvil

For these tests you need a file, a hammer, a lodestone, a forge, and the good sense God gave a goat.

First is the MAGNET. Copper, brass and bronze will not jump to it. If the piece grabs, you are holding iron dressed in copper's Sunday clothes.

Second is COLOR, and never the color of the outside, for tarnish is a liar's coat. File one clean spot. Fresh copper shows a warm salmon pink, the color of a healthy gum. Brass shows lemon yellow up to brassy gold, and the more zinc, the yellower. Bronze shows a duller reddish gold with brown in it.

Third is the FILE BITE. On soft annealed copper the file sinks in like a spoon into butter and clogs with pink curls. Brass files clean and fast and sheds fine yellow dust. Hard tin-bronze makes the file skate and squeal like a pig at a fence.

Fourth is the RING. Hang the piece on a string and tap it with a hammer. Copper gives a dull thunk, brass a brighter clink, and bronze sings long and pure. Tin buys hardness but sells toughness. Bell metal, about four parts copper to one of tin, is brittle. The Liberty Bell at Philadelphia is a high-tin bronze, and its crack opened past mending in 1846. Gun metal, about nine parts copper to one of tin, made the Union's 12-pounder Napoleons. Bronze was made to shoot or to sing, and it will not bend into a worm without cracking.

Fifth is the FLAME, and here we are in alchemy country. Sprinkle clean filings into a spirit lamp and copper colors the flame green to blue-green. Heat brass past a bright red and the zinc boils out as a white smoke, which settles as philosopher's wool, or flowers of zinc. Do NOT breathe it. It brings on brass-founders' ague: chill, fever, and an iron taste in the mouth. Do this test out of doors, upwind, and quick.

Why Zinc Has No Place in the Worm

Your pot and worm sit in hot, sour wash and hot spirit, run after run. Brass in that bath gives up its zinc a little at a time. That is dezincification, a ten-dollar word for rot. The zinc goes into your spirit. What is left of the brass is a spongy, porous ghost that weeps vapor from a hundred pinholes one morning. Pure, clean copper does honest work besides: it takes the sulfur stinks of the ferment out of the vapor and holds on to them. Use clean copper, joined with silver solder or a good mechanical union.

Annealing copper is a different animal from tempering steel. Heat it to a dull red, then let it cool in the air or plunge it in water. Either way it comes out soft, because quenching only saves the waiting. I anneal my coins the same way now. The new bronze cent of the Coinage Act of 1864 bounces my punch off like a temperance lecture off a teamster. Barnaby, my Cooling Supervisor, has cooled exactly one piece of copper, by sitting on it. He is a tall tale on a chain. No sensible man keeps a bear near a forge.

Ashes, Oak Shavings and Bitten Coins

Rabbit Miller of Wilkesboro asks whether hickory ashes or red oak shavings in the thump keg will clean out bad heads. Ash is potash, which is an alkali, and it will soak up some of the sour vinegar acids. But potash meeting the oily tails in a hot doubler makes soap, and the spirit comes out tasting of Monday laundry. No ash pulls methanol out of vapor. The only cure for bad heads is a generous cut: when in doubt, throw it out. Oak shavings give tannin and an amber color, which is a lie of the eye. Real age comes from time in a barrel.

As for biting coins, a gilded lead slug is softer than gold and passes the bite test with honors. I have pulled more molars from coin-biters than from candy-eaters. Ring the coin on a stove lid as Granny Vance did, or file its edge. And mostly copper is like mostly sober: if it files yellow, it stays out of the still. Keep your copper clean, your cuts honest, and your fire low.