A dry washer is a machine used to separate gold from placer material without using water, functioning similarly to a small waterless sluice by means of air pulsations through a cloth medium.
When Dry Washing for Gold, Hand winnowing or dry panning are more time-consuming methods of processing gold-bearing gravels; hydro prospecting provides much faster results. It is especially popular in desert environments with limited access to water.
Shaking Tables
Shaking tables (gravimetric tables or shaker tables) are widely utilized in gold mining and e-waste recycling processes. Shaker tables use density differences to effectively separate precious metals from glass fiber, plastic structures, and other heavy materials based on density variations. Generally, narrower grain sizes lead to superior performance for separation tables compared with other gravity separation equipment; hence many miners prefer using shaker tables over other gravity separation equipment.
Shaking tables are an ideal solution for Dry Washing for Gold: due to their relatively low capital and operating expenses, as well as alluvial mining applications; their capacity however, may be limited so in order to maximize their benefits a prospector should prepare several size fractions prior to treating on the table.
Feeding gold-bearing material into a shaking table involves placing pay-dirt in a hopper, which is then shaken using a drive mechanism with bicycle gears, chains, and rubber bands made from car tire inner tubes - with its movement creating riffles on the table surface that help separate out lighter materials while collecting heavy ones like gold.
Under this method, a miner must periodically clean their concentrates to remove any sand or clay that has made its way into them - similar to how cleaning of sluice boxes works.
Shaking tables also boast the ability to produce high concentrations of gold, making them especially helpful in areas without access to enough water for wet panning, sluicing, and suction dredging.
Shaking tables have one major drawback in that their paydirt must be nearly dry - meaning free from more than 3 percent moisture content - for effective table action to take place. As such, wet washing methods like those discussed above often come into play alongside dry gold mining. Yet the gold concentration ratio offered by shaker tables often beats that of other gold concentrating devices, making it one of the most sought-after tools for dry mining operations; some even adapt them for producing other metallic minerals and metals!
Sluice Boxes
Sluice boxes are pieces of equipment used by prospectors to extract gold or other heavy minerals from black sands and gravels. A sluice box consists of a slightly sloping wooden trough fitted with transverse riffles and carpet or matting that trap gold particles as water washes them down the sluice box, trapping gold from falling through its flow into a trapper box that has transverse riffles attached for water drainage; commercial mining operations may use larger versions than smaller boxes when used by prospectors to recover gold or other heavy minerals from black sands and gravels.
For anyone working to dry wash for gold, the first step should be classifying their material to eliminate contaminants like iron and pyrite from contaminating their sample or being misinterpreted as valuable minerals like gold. Once this process has begun, a sluice box should be set up, slowly filling with scoops of classified material from classification. Be careful not to overfill as overflow can clog riffles allowing gold through without being caught - once the fullness level has been reached just below these riffles then comes cleanup time - which means either by itself or another process!
Slowing the flow of water over riffles allows heavier material to drop from behind them while lighter gavels wash down through the sluice, effectively separating heavier from lighter materials and creating a concentrate that can then be rinsed into buckets for retrieval of any gold that might remain.
Sluice boxes were once limited to areas with constantly moving water; but today, thanks to advances in dry recovery technology, anyone can now use a sluice to retrieve gold from dry creek beds or desert washes that never see running water.
Clean-up after each and every processing session should not be neglected, particularly if using the sluice box in an area with rocks that could scratch or damage matting. Furthermore, it would be wise to rinse off riffle section, screen and carpet as well as any gravel or sediment accumulation from their use as this may help ensure optimal performance of these devices.
Motorized Dry Washers
Dry-washing can be an efficient method for gold prospectors without access to water, providing them with an effective means of extracting valuable materials from waste sand and gravel. Conceived as an alternative solution to standard wet sluices, the dry washer relies on vibration and air pulses to concentrate and separate valuable minerals like gold from their surroundings.
A basic dry washer consists of a frame with a screen enclosed within, covered by fine linen fabric. A bellows is then used to blow short, strong bursts of air through canvas material for simultaneous shaking and classifying actions. In addition, there may also be one-half to three-quarter inch L-shaped steel or quarter-round wooden molding riffles placed 4 to 6 inches apart that provide additional shaking action.
The riffles are designed so that heavier mineralized material gravitates down and past them while lighter valueless material is rejected over the top of them, effectively trapping gold in its upper riffles while less desirable material falls to the bottom of the box. Unlike panning or sluicing which require chemical additives for processing gravel, dry washing requires no such additives for processing gravel.
As no water-free system can ever be completely effective, some loss of coarse and fine gold may still occur during any dry wash process. To reduce this loss as much as possible, utilizing a metal detector prior to performing any dry wash process is recommended.
When using a dry washer, all materials must be free from moisture as any dampness will cause the clay to clump and prevent full recovery of materials. Unfortunately, it can also be a noisy device, and taking several hours or even more to complete one cubic yard of material will take time and patience.
Keene's hand-crank mini dry washer is portable, relatively affordable, and straightforward to operate. Equipped with a Marlex hopper equipped with an adjustable flow control valve to regulate material feed rate. A hand-turned crank controls vibration so dense materials settle while heavier gold drops through its riffles - further increasing fine gold recovery rates. Additionally, dual riffles enhance fine gold recovery.
Portable Dry Washers
Dry washing is one of the oldest and most reliable ways of extracting gold from dirt in dry environments such as deserts. A dry washer separates gold from dirt without water use - similar to highbankers but more portable and affordable; making it an excellent option when prospecting remote locations that lack sufficient supplies of freshwater.
A basic dry washer is essentially a long, waterless sluice that separates gold from sand through air vibrations and pulsations instead of running water. Screened gravel passes down an enclosed box with cross riffles into canvas or other light-weight cloth medium, where bellows blow short, strong puffs of air over the riffles to shake and classify materials; heavy materials fall through dead air space between riffles while finer ones move up through them.
At one time, many dry washers were hand-operated and utilized bellows to puff air across multiple riffles in a series. Light material would fall through these riffles into a hopper below; today most use small blower motors which provide constant airflow over moving riffles and shaking material into place. More advanced units may include features such as grizzlies or even sluice boxes to recover any finer gold deposits.
When using a dry washer, patience and diligence are the keys to the successful recovery of all valuable gold that has become trapped within concentrates. In most instances, multiple passes must be run through your dry washer before any of this gold can be extracted from within your concentrates; additionally, keep in mind that certain fractions of very fine gold may be lost through all dry recovery methods.
Modern improvements to dry washing equipment have made it far more practical and effective, even among experienced prospectors who may prefer wet prospecting methods like sluicing and highbanking. A good-quality dry washer will last you for years of service while the appropriate model can allow you to explore desert areas largely ignored by previous mining operations.