This article unveils the workings of a dry washer, an invention so simple yet brilliant that even the average reader can appreciate its ingenuity. The dry washer, reminiscent of a medieval or renaissance machine, could even be mistaken for a device of torture!
The Hopper Box
At the top of the machine is a hopper box, covered with a 1/4-inch screen through which dirt is thrown. Each shovelful is "classified" into material free of rocks or pebbles larger than a quarter inch. Weeds and organic matter are also filtered out. I always examine the rocks that fall off after each shovel full to ensure I haven't missed a colossal gold nugget.
Despite classifying tons of material over the years, I've yet to find such a nugget, though I still dream about it! Many people use metal detectors to scan the rocks that pile up in front of the machine, adding real meaning to the phrase "gold is precious." There is a sheet metal chute at the top that guides the rocks away from the machine to prevent them from piling up at the legs. At the back of the hopper is a rod that, when pulled, opens a trap door to allow material to fall onto a riffle box.
The Riffle Box
A riffle box is essentially a rectangular tray with small rails periodically placed across it to slow down the material being jostled through. A bellows below drives up and down, tapping the box and blowing air against and through the cloth that forms the riffle box bottom. This process helps separate gold from other materials because gold is 19 times heavier than water. When gold hits a riffle, it sinks and stops. By the time the material reaches the bottom riffle, 98% of the gold flakes are trapped behind the riffles, or so claim most commercial dry washer manufacturers.
Once only the material behind the riffles is left, it's time to empty the riffle box, as this dirt contains the gold. A bar that straddles the riffle box, holding it in place when down then allows it to be removed when up.
Automatic vs. Manual Dry Washers
Most modern dry washers are equipped with electric motors to drive the bellows. They are often made of lightweight aviation aluminum with folding legs, hoppers, and riffle boxes for portability. My dry washer, however, is manually cranked. While this means I don't need a battery and motor, the downside is that it's heavier and doesn't fold up, making it cumbersome in rough terrain.
Despite these challenges, I find my dry washer useful. It cost around $200 compared to the $500-$600 price tag of motorized versions. There are pros and cons to everything. Sometimes, I carry buckets of dirt from the dig site to my parked truck to process the material. This method has saved my wife's roses from the massive dirt piles I used to create in the backyard when panning at home.
The V-Shape Design
The V-shape design of the machine enhances the flow of dirt. Some people find it odd, but I initially thought the noise and bellows motion made it look like it was about to take off! The pulley and belt drive connects to a crank lever under the bellows, pushing it up and down. Adjusting the shaft at the hopper controls the dirt feed onto the riffle box.
Gold Blasts Off
With gold selling at around $2700 an ounce (Jan 2024), more people are interested in collecting gold placer flakes. These enthusiasts prefer digging riverbeds, streams, dry washes, ancient waterways, and arroyos where gold flakes have been deposited.
For those who enjoy outdoor exercise, camaraderie in a club, and a bit of gold fever, I recommend finding a local treasure hunting club. Google GPAA to find clubs in every U.S. state. While GPAA has the most clubs, there are unaffiliated clubs, too. As for curing gold fever—I haven't found a remedy yet!
The Keene 160 Mini Dry Washer
One intriguing rather new dry washer is the Keene 160 Mini, combining a dry washer and high banker into one compact unit weighing 29 pounds. This is a game-changer for those with respiratory issues, as it offers a dustless operation, making it ideal for prospectors with asthma. Although I can't afford it, I was impressed when I saw it in action at gold mining shows.
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