Threads & Yarns

Although silk threads are sometimes used to replicate traditional patterns, most are manufactured from synthetic materials.  Silk is not as robust as synthetic and over time will weaken even further.  Synthetic threads are manufactured in a variety of sizes from very thick 3/0 to very fine 20/0, in the X/0 system the higher the number the finer the thread.  A problem with the X/0 system is that there is no standardization between the manufacturers.  In the denier system, 1 denier = 1 gram which is the weight of 9,800 yards of that thread. So, the higher the denier the heavier the thread, it is measured in weight not strength or thickness.  Having said that, all things being equal, the higher the number the thicker and stronger the thread tends to be. An 8/0 uni-thread is roughly 72 deniers, and a 6/0 is about 135 deniers. Also bear in mind that there are no industry standards for the size of thread, so one manufacturers 14/0 could be the equivalent of another’s 12/0, 14/0 or 16/0.

Most threads available for trout size flies are either nylon or polyester, with nylon being slightly weaker but exhibiting more stretch.  Polyester threads are more durable and less prone to degrading over time. Threads are also available as waxed or unwaxed, where they are given a light coating of wax during manufacture.  Although rarely sufficient for dubbing it does make the thread resist fraying and aid in forming the finishing wraps.  Some tyers find that unwaxed thread allows the filaments to separate easier giving greater latitude in controlling the shape e.g. in flattening it.

There are four basic thread structures, flat or continuous filament thread, simple-twist thread, rope twist, and round which is a monofilament thread. Each has qualities that are more appropriate for certain flies than others. Rope twisted thread is stronger but normally reserved for tying salt water flies and deer hair.

To flatten your thread just counter-spin it, however, Uni is a corded thread which will not flatten no matter how much you spin it. As is Veevus 6/0 and 16/0.

As a side note, I use Sheer 14/0 thread for most of my trout flies. This is a very fine tying thread; it is lightly waxed but has good strength for its size.  I find that it results in very little build up, enabling small and neat heads as well as splitting very easily for dubbing or CDC fibres, this gives me a much neater fly rather than using an 8/0, (we can’t all be Davie McPhail!!).

GSP (gel-spun polyethylene) threads are super slick, strong for their size, have very little stretch (3 percent), and lie flat on the hook. They are typically used for spinning deer hair or for synthetic materials that call for an abnormally strong yet small-diameter thread. Although if very fine thread is used you have to be careful not to have it cut the deer hair fibres.

The slickness can be a liability in other applications however, particularly dubbing retention, and the dye used to colour them is not as stable on GSP thread as it is on other materials, so is normally only available in white. It may also cause extra wear and tear on your bobbin holder.

Nano silk, is very strong and multi strand.

Kevlar thread, is very strong but stiff. Not used so much nowadays as GSP has replaced it.

Floss is much thicker than thread, and is available in similar colours. Rayon is the most popular type, being smooth and shiny making it an ideal body material or as a rib for a variety of flies. Also, it can be used as breathers for buzzers, the yellow can be used as substitute jungle cock eyes.


As a starting point (to a vast subject!) the purpose of a hook is to hold the materials for the fly and then secure the fish when it takes the fly. In trout flies the hook models are primarily defined by the length of the shank and the diameter (gauge) of the wire, and the gape. Wet flies would be tied on a standard wire and a standard-length shank. Dry flies are tied on light  wire hooks, and nymphs are tied on heavy hooks. Lures would be tied on standard diameter hooks but with extra-long shanks. The smaller the hook the bigger it’s number, the larger the hook then the smaller it’s number. Allowing for the fact that there is no standardisation for hook sizes, each manufacturer sets their own sizes. It can get a bit more complicated with variations from the standard, these are described using Xs. For instance on a size 14 hook if it says 2X, it means that the shank is 2X long the equivalent of a size 10, however, the gape and the gauge stay the same.

As an example most dry flies will be tied on hook sizes 12 – 20. Nymphs will be tied on 10 – 16s and lures on 6 – 12. However, these are not set in stone and there can be lots of variations.

There are literally hundreds of different hook styles from different manufacturers.

Very few hooks are man-made and the vast majority are made by industrial processes.

The basic anatomy of the hook is important since its various parts are often used as reference points in sizing and mounting materials, to achieve the desired proportions.

Varnishes, Epoxy Resin & Superglue

Varnish or head cement is a lacquer (clear or dyed) that is primarily used on the head of the fly to secure it.  It is also used on the body before wrapping some materials like quill to help strengthen the fly, and on posts to stiffen them. Head cement is solvent based so can penetrate the wax on the thread down to the hook. Their adhesive strength is not particularly high, but useful as a light-duty glue. Another useful varnish is Floo Glue which is a flexible lacquer that can be used on wing slips to keep them stable. You can apply it before tying in or after, bearing in mind that once applied if the wing then splits you cannot repair it. 

Sally Hansen is a nail polish product which doesn’t penetrate as well but it does produce a shiny head.

UV resin has replaced old fashioned epoxies and was originally developed to repair surf boards. Available in different viscosities is very popular for creating hard smooth surfaces which can be hardened in seconds, with the use of a UV light. As with the varnish it is better to apply two thin coats than one thick coat. Resin is heavy so it is best not to use on dry flies. It adds durability to the fly but needs to be adhesive and not cohesive, in other words it will stick to the fly and not itself. It can help the adhesion if you start to cure it holding the lamp further away from the fly. It doesn’t penetrate as much as head cement does so a layer of head cement then another layer of resin could be the best solution. Some people are allergic to the resin and its fumes.

Super glue (cyanoacrylate), offers superb adhesion but some can turn white when wet. It is best used on the inner workings of the fly, such as fixing lead eyes. Caution needed when using so that you don’t get it on your fingers.

Spray fixatives are used by draughtsmen and artists to protect drawings. For tyers they can be used to reinforce delicate feathers, and when dry they are slightly flexible.


After a few years of fly-tying if you sit down and work out how much you have invested in materials, it can be frightening.  Certainly, the last thing you need are moths and parasites ruining them.

Feathers, hairs and other susceptible materials should be stored in sealable pouches in organised drawers.  I have my saddles, cock & hen capes all in individual bags in deep separate drawers.  Extra protection can be given by keeping your windows closed at night, so that the lights don’t attract moths. Avoid scents such as evening primrose and honeysuckle which are designed to attract moths as pollinators.  Instead use lavender and in particular bay leaves sprinkled around the materials. You can also use proprietary insect repellents, if you don’t mind the aroma they can produce.

Obviously beads and synthetics don’t have this concern, but they should be organised in such a way as that they are readily available to the tyer.

Never introduce natural materials from a suspect source, to your collection.

The best advice I can give on storage is to make sure you are organised, so that you are not ordering materials you already have but can’t find. This is especially true of things like hooks, the photo shows a great space saving idea for hooks.