[Philmont]: RE: Fuel Filters

Capillarity, the ability to wick up through narrow spaces such as between
the fibers of a filter, is a unique property of water. This is the basis for
using a filter to remove small amounts of water from fuel. Since fuel is
less dense than water and floats on top, large amounts of water should not
be an issue because you can simply pour the fuel off and leave the water
that is at the bottom of the container behind. Small amounts of water in
fuel will wick into the fibers of the filter while the fuel passes through.
Once the filter becomes saturated it will not be able to remove additional
water. Theoretically, any fibrous filter material will do, even your
Cool-Max tee-shirt. I have read of small plane pilots in the old days
filtering the fuel for their aircraft through burlap sack material. As for
coffee versus felt filters, one of the characteristics of filters is called
"depth." It is an indication of how much material the filter can trap before
it becomes saturated and can hold no more. Obviously, a thick piece of felt
will have more depth than a thin piece of paper. This is the only real
difference between filtering fuel with one or the other. I haven't seen one
but I would guess that the felt from the older Coleman filters is even
thicker (maybe as much as 1/8 inch?) than the felt from a fabric shop. If I
were going to make my own filters from felt fabric I would use about four
layers to get some additional depth. You could double or quadruple a coffee
filter for more depth as well, but it still would probably not have as much
depth as a layer or two of felt. The other really important thing to
remember about filters is that they function to trap particles of solid
material suspended in the fuel. If a little water in fuel can mess up a
stove, think about what a bunch of solid particles might do. This alone is
a good argument for always filtering fuel with a proper, well-cared for
filter.

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Received on Mon Mar 1 10:26:41 2004