Dry Washing Operations

Dry washers are normally operated by hand and can support around the same amount as normal rockers that are of the same size. Running a dry washer is a lot harder work nonetheless. The miner’s that use these need to choose the material they are going to be working with considering the dryness and the likeness of gold content. This is not an easy thing to do on a large scale basis with hired labor though. There have been many attempts for dry washing of all kinds such as plants with mechanical excavators, power driven dry washers, etc, but these have all resulted in complete failures commercially, mainly because the gravel was dug faster than the sun was able to dry it. One other thing in large scale mining is that mainly with mechanical excavation, the cost of sizing the material can be outrageous. In cases where there is clay or cemented gravel it can cause even bigger problems to deal with. After the gold bearing material has dried and disintegrated completely, panning tests of the tailings will need to be done and these should demonstrate that if it is really worthwhile to continue on before any more work is done. It is not normal to get completely disintegrated material though. The surface of the streaks of clay in the gravel is probably richer in gold than the gravel itself. Cemented and clay gravel cannot usually be broken by hand in order to get to the gold without the use of some sort of pulverizer. Unluckily, in a dry washer, the gold that comes in a lump of waste goes out of the machine. Given that water will usually break up all of the gravel and separate the gold, more savings can normally be done with a rocker or sluiceways than it can with a dry washer.

What is a dry washer?
A dry washer takes care fundamentally of separating gold from sand by pulsations of air through a porous device. The gravel that is screened then goes on down to an inclined riffled box that has cross riffles on it. The bottom of the box is made of some sort of canvas or porous material. Under the riffle box there is a bellows where the air is strongly blown through the canvas. This is what then shakes and classifies the material. Given the weight of gold, it gravitates to the canvas and is held by the riffles and the waste gores through and out of the machine. The gravel will need to be shoved into a box. After there are a few shovelfuls inside the box at the head of the washer, the gravel runs through it. There is a screen that has around an inch half openings that is utilized on the top of the box which takes care of getting rid of the bigger stuff, depending on the ground and should also be checked to see if any nuggets are present. Dry washers are usually run by little gasoline engines. The capacity of these machines is much great than the ones that are hand operated. For example, one man that is working on his own is able to treat around one half to one cubic yard every day with a hand operated washer. If two men are working, one of them takes care of the shoveling while the other takes care of turning the crank. After it is time to pick up, the material that is behind the riffles is normally dumped into a pan and is washed out in water. If there is not a lot of water, the substances that have accumulated from the riffles can be placed into the machine another time and then cleaned more by blowing the lighter materials away in a pan for example. The cheapest dry washers are made by hand and have been built a great deal, and come in a range of different sizes and designs.