How do riffles work

The reason that riffles work is two fold. First, there is an eddy created behind each riffle, causing a temporary lull in the water flow. The material that is flowing is in a liquid state. This causes the heavies to be at the very bottom of the flow. As the flow passes over a riffle, the heavies will fall to the bottom behind a riffle.

Second, the riffles are spaced a couple of inches apart, and act as a series of small dams, stopping the creep of the heavy material down the sluice. Without them, there would be a slow, but sure creep of gold out the end of the sluice.

Normally most of the trapped gold will be behind the first couple of riffles. This is because the heavies fall fast. Small flour gold may extend several riffles further, and, hopefully, the last few riffles have ZERO gold. If you find gold in the end of your sluicebox you surely have lost mor eout the end.

The riffles are usually hinged at the upstream end, with a latch at the downstream end. So you can release the latch, and swing the riffles up. Usually there will be a 3/16th inch layer of material called miner's moss or carpet, that resembles in texture, a kitchen scouring pad, laying on the surface of the sluice. It is a loose weave matt with lots of air space. It traps and holds the smallest gold particles. On top of that can be a layer of expanded metal. This creates a criss-cross pattern of spaces, each with their own eddies. Then the riffles, that resemble a ladder, with each riffle a rung, when swung up, is lowered into place and latched down.

Each time you clean up, you raise the riffles, and remove the moss. You then wash down the sluice, wash out the moss, and put it back together, all inside a tub, of course. How often you do this depends on whether you want to know what you're getting, whether to move or not. Otherwise, you can probably run the sluice for quite a while, before cleaning (I used to think that you should clean it often, but I tend to think otherwise now). The gold is going to fall out early in it's travels down the sluice, and it would have to fill up with gold, before you started loosing anything.

The way to tell if you have things close to right or not, is to notice whether you are finding gold many riffles down from the front of the sluice. It should be very close to the front, in the first 1/2 of the sluice for sure. One way to always know is to make the miners moss two sections, butted together. All the gold should be in the first mat. There should be nearly nothing in the second. I have divided mine into 4 sections. I pan the last section to make sure that there is nothing in it. I pan the first section to see what I'm getting.

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