Fibers For Fly Tying  Improving our chance of catching fish is the reason most of us part with big bucks for lessons, seminars, books and tapes. The particular ingredient that we search for is knowledge. Within this vast knowledge pool we all share as fishing enthusiasts the emphasis is usually on "how to" instructions and demonstrations. This works well because we are blessed  in this sport of fishing with numerous skilled and talented practitioners. Your knowledge resource does not have to end here and it shouldn't. All many of us do for years while learning this sport is to copy or imitate exactly that which we have seen. With a bit of knowledge that expands beyond demonstrations you can have a much greater advantage as a fly fisher. You will be able to improvise and make choices when circumstances require it and you will be equipped to experiment. This special awareness is simply to know "why" we do the things we do as well as how to do it. Providing inspiration to seek out this kind of information is the goal of the material presented here.  Things You Wanted To Know About Fibers (And A Few Things You Probably Didn't)   A lot of us when first getting started in fly tying follow the material lists or "recipes" to the letter. For many it becomes almost an obsession. If a particular fly calls for a certain ingredient, by gum, we better have that exact stuff or we are just not going to tie that fly. Actually, substitutions can often be made. Various fibers are the most common material used in tying flies and in much of the gear we use. They exist in an endless selection from ancient flax or other grasses to fur, cotton, silk and modern man made exotics such as polymers, boron, glass and graphite. Each of these substances posses unique properties. As fly fishers it is these properties that we try to exploit when choosing a fiber ingredient for a fly. With the possible exception of some caveman (Hey! This is no GEICO commercial.) that might have touched his finger to a gob of pine sap on some pre-historic tree and drawn it away slowly to notice a tuft of resin fibers, man made fibers historically speaking are relatively new. Through the process of evolution natural fibers however, have evolved for millennia and with some very unique properties. With all of man's  technology there are still some natural fibers that science has not even come close to replicating. Hairs from the tail of "Kolinsky Sable", a marten which lives in the cold river valleys of Siberia are used to make the finest water color brushes. Larger sizes (less than 1/2 inch at the base) of these brushes commonly sell for $500.00 to $600.00  Thank goodness no popular fly lists this material as an ingredient. Once again, it is because of their qualities that fibers are chosen to become part of a fly. These brush hairs can be bent over millions of times and always spring back immediately to their original straight form. Some properties of fibers are obvious such as color, general shape and relative size, but many characteristics go unseen. Cotton, a type of cellulose (plant) fiber appears to the eye to be plain fine threads but if you look at them magnified under a microscope you will see they are actually hollow tubes flattened and twisted like a bunch of mistreated drinking straws. (See Fig.1) below.   Because they are hollow they exhibit a particularly useful property. All these little open ended tubes demonstrate capillarity. Without going into too detailed a discussion this simply means that water is attracted or drawn to the inner walls of a fine tube and will travel up each tube above the surface of the liquid.  Now, if you want a fly to absorb water and sink, construction with cotton fibers will do that for you. In order to compare these properties of different fiber substances to each other they are measured against a set of standards. For our purpose as fly fishers we need not delve too deeply into these standards. Besides, they have long names that normal people have no earthly reason to remember. What you do want to be aware of is that natural animal fibers such as fur have much wider variations from sample to sample in almost all their properties as opposed to synthetics but they have been designed by nature to do a specific task very well. Again as with the cotton fibers you sometimes need a microscope to see the detail that make these materials so unique for our purpose. Hairs from animal pelts are not smooth they only appear that way to the unaided eye. Each species have a unique pattern to the unevenness or even "scales" on each hair.  These patterns help lock adjacent solid fibers together when small clumps are tied into a fly. Unless very specially treated, synthetic fibers are totally smooth. See Fig.2 below. When tied they depend on more pressure from the tying thread or glue to keep individual fibers in a clump from falling out. As an added incentive, in many cases fur material contains natural oils that prevent water from adhering to the fibers and migrating into the spaces between adjacent fibers. This is just what you want in flies that float. Ask anyone who fishes with flies tied with snowshoe hare, they seemingly float forever. With the limited space available here an "in-depth" treatment of this subject is not possible. At best we can only touch upon information that sometimes gets overlooked. Hopefully you've seen that the characteristics of common fiber materials used to tie flies are not always obvious. If you tie flies, it is a subject worth looking into. Several books in the Fly Fishing literature address the subject. Chapter 5 of Darrel Martin's "Fly-Tying Methods" is a good place to start.   If you'd like to take an actual closer look at the materials you tie with, you don't have to invest a fortune in a laboratory microscope. A wide assortment of reasonably priced optical magnifiers useful to fly fishers are available from Edmund Scientific Company, 101 East Gloucester Pike, Barrington , NJ 08007-1380. To get their free catalog call 609-573-6250