This type of equipment is used where water is not available and the dirt is very dry. Even slightly moist dirt will cause problems and gold will be lost. This method is not as efficient as wet methods since the material will not break up as well when dry and some gold will be locked up in dry clay or stuck to larger rocks or organic material and lost. As mentioned under “Classifiers”, it is important that the material to be worked has a consistent size and this is even more important when using dry methods. Thus a smaller screen size is usually employed for dry methods and one must be careful to examine material that does not pass through the screen. Dry methods are more likely to lose very fine gold than wet methods.
When set up and run properly, they have very good gold recovery. Whereas most equipment uses a riffle box with a solid base, a dry washer has a cloth base. Instead of relying on water, these utilize air by having a blower or bellows force air up through the cloth bottom of the riffle box to agitate the material and cause the lighter material to “float” to the top, where the very lightest material is blown off, and the remainder of the light material floats off the end of the riffle box. The heavier material collects around the riffles. This can cause quite a dust cloud around the equipment. Most dry washers also have a vibrating action to help the gold to settle. This can be as simple as a weight attached to a fan in the blower to make it unbalanced and thus cause a vibration. Some of the newer dry washers even use the heat from the blower exhaust to help dry out any moisture that may exist in the material.
There is a large variety of dry washers available, both home made and mass produced. Some are manually operated while others are powered, either gas or electric. The gas powered machines use a leaf blower type of motor which blows air up through the cloth bottom while manual and electric usually use a bellows type arrangement. They also come in a variety of sizes. Many club members use a dry washer and you can see quite a variety at the outings. Jack and Gene even found some gold with the small battery powered dry washer shown here. Some manual dry washers can be easily converted to electric. Oddly enough, the desert is too damp for dry washing much of the year, especially as you dig down towards bedrock.
