If you have decided to upgrade from a gold pan to a sluice box you’re far from alone. A sluice box is one of the best upgrades you can make as it will help you process many times the streambed material compared to a gold pan. However, there is a lot to learn, and in this article, we’re going to look specifically at how to angle your sluice box for maximum performance.
A sluice box should be set with a 4-8 degree angle. Another rule of thumb is that the sluice should be angled to drop roughly 2 inches per foot of length. The exact angle depends on the size and weight of the material, the riffle design, and the speed of the current.
As you see, there is not a universally applicable answer as to what angle is the correct one.
However, it’s certainly not rocket science, and in this article, I will teach you some easy and simple tricks for setting the right angle for your sluice box.
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Capturing Big Vs Fine Gold: Important Distinction
Before heading out there prospecting it’s always a good idea to make sure you have a general idea about the gold you are looking to collect, and more specifically, its size.
The reason is simple. Capturing bigger pieces of gold like gold nuggets is really easy.
They are simply so heavy that virtually any type of gold trap will do the job. It doesn’t matter if you run too much water through the sluice or put it at a bad angle. The gold will get caught anyway!
However, when it comes to fine gold, things tend to get harder.
Even if the density of the gold is just as high, every bit will be tinier and lighter. This makes the gold much more prone to getting grabbed by the water flow and later discharged out of the sluice.
With that said, most gold found is fine gold. Only around 2% of the gold mined today is estimated to be gold nuggets, according to some figures. Thus, taking the time to get the angle right is definitely a good idea!
Setting The Right Angle (and Water Flow)
It’s important to understand that the angle of the sluice box goes hand in hand with the speed of the water flow through the sluice. For instance, too slow of a flow can be compensated to some degree by increasing the angle of the sluice box itself.
Now, getting the water flow right is really important in and of itself, as having too much water traveling through your sluice could severely reduce the gold recovery rate of your device.
If the flow is too fast, the finer gold will simply get lifted up by the water flow and escape the sluice at the back.
Similarly, if the flow is too slow, the riffles will get clogged with a lot of sand and pebbles which will practically make them useless as gold traps.
Just to give you an example, have a look at the diagram below. It shows the recovery rate of gold, categorized into three size classes, in different water flows.
As becomes apparent, the recovery rate of fine gold goes down quickly if the flow speed gets too high. The coarser gold, while showing the same tendency, is much less affected by the flow speed. Again, this is because each individual gold bit is so much heavier.
How Much Water Should you Run Through Your Sluice Box?
So, how water is enough? Well, here is a simple rule of thumb.
You should run a sluice box with as slow a flow you can without clogging the riffles, always leaving some matting visible between them. If there is white froth as the water flows over the riffles, it’s way too fast and will blow out most of the fine gold.
Another rule of thumb is that the flow should be fast enough for the material to move through the sluice rather fast. A few seconds usually is a good mark to strive for.
How to Get the Water Flow & Angle Right: Three Tips
To achieve the water flow described above, there are several things you can do:
- Find a good spot: First and foremost you should try to find a spot in the river where the water flows reasonably fast. Put down the sluice at a reasonable angle (perhaps around 5 degrees), and observe the flow. If it looks alright, feed it some sand and gravel and see how it flows through the sluice.
- Adjust the angle: Now you may try to adjust the angle of the sluice box to compensate for a too fast or slow flow. For instance, if the riffles are starting to clog up, you can increase the angle somewhat. However, the big adjustments should be taken care of by adjusting the water flowing into the sluice.
- Build a funnel: If the stream isn’t flowing quickly enough, you can always build a funnel of rocks that are heavy enough to not be moved by the current. Sometimes just placing a couple of rocks around the entrance of the sluice might do the trick, and provide just the extra water that is needed.
So, in summary, it’s all a balancing act between finding the right angle and water flow. And as long as the water isn’t flowing too fast and the riffles aren’t clogging up, you are probably doing a fine job.
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For more instructions be sure to check out my full guide to setting up a sluice box.
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How To Capture More Fine Gold (5 Tips)
Most people who wonder about the right angle for their sluice box are looking to optimize their fine gold recovery.
So, I thought it would be a good idea to tell you about some other things you can do to make real noticeably improvements to the gold recovery rate of your sluice box.
Let’s begin!
1. Classify Before Feeding the Sluice
If you remember, I told you that you want the water to run as slowly as possible without clogging the riffles. Now, if you have a lot of big pebbles that go into the sluice, that will obviously require a faster flow to keep the riffles from clogging up.
This is why it’s always recommended that you use a classifier to sift out the bigger rocks, pebbles, and debris. As a result, you can run the sluice with a slower water flow, resulting in an increased recovery rate.
2. Use Expanded Metal Riffles
Some types of riffles are better than others when it comes to fine gold recovery.
Studies have shown that the expanded metal riffles result in higher gold recovery rates than normal, L-shaped, or Hungarian riffles.
3. Don’t Overload the Sluice
Although most sluice boxes are quite forgiving, you should not dump all your material at once. To ensure maximum gold recovery, all the sands and gravels must be given enough time to be soaked properly and turned into a slurry. Otherwise, much of the fine gold could flow right past the riffles and other gold traps.
4. Don’t Leave it running without adding new material
In many cases overloading also means that the sluice is left for long periods without any new material being added.
Just like in the case of overloading, this could lead to some of the finer gold getting lost.
Simply put, as the flow of water removes the lighter sand particles, the gold beneath gets more and more exposed until it risks getting flushed out of the sluice.
5. Install Matting Below the Riffles
A good way of ensuring that any gold that falls to the bottom doesn’t float up again and escape the sluice, is installing mattings below the riffles.
There are several types of mattings on the market that will do the job, but in my experience, the so-called “spaghetti loop mattings” are the best.
Conclusion
Setting the right angle for your sluice box is not rocket science, but it requires some basic knowledge if you want to get it right. To summarize, you want the flow speed to be as slow as possible, while still being strong enough to swiftly move the material through the sluice.
In addition to setting the right angle and adjusting the water speed properly, there are several things you can do to increase fine gold recovery. Some of these include putting mattings below the riffles, opting for expanded metal riffles, and keeping a proper material feed rate.
Happy Prospecting!
