Thread is often overlooked due to its construction role in fly tying; considered a “necessary evil” given its bulk adds weight on small flies, and uneven application leaves lumps and bumps in your fly’s body, causing issues with smooth materials like tinsel and floss. While its water absorption is minor, it will trap moisture and contribute to an eventual sinking. To add insult to injury, the small sizes, 8/0 and smaller, tend to part like toilet paper, and have a nagging tendency to break on critical steps leading to catastrophic unraveling and constant swearing …

… and that’s the Good News ..

Like everything else in fly tying, skills come with time and practice and thread is no different, so let’s focus on a few underlying issues that are not so obvious.

Thread, Proper storage and care

Most threads are made of synthetic materials, nylon, polyester, and GSP (Gelspun) – a member of the polyethylene family. The enemy of all synthetics is sunlight, so if you store thread in a tool caddy in direct sunlight, bad things will happen over time. Gossamer threads, 16/0 and beyond, will decay quite quickly, where size “A” thread will be less affected due to the increased volume of material they contain. Heavy threads resist sunlight better than thinner threads, and all will sustain damage over time.

If you have issues with thread breaking, ask yourself whether the fly shop you frequent store their threads in direct sunlight. Is their display near a window in full glare of an afternoon sun? If so, the less commonly used colors, those that remain on the rack longer could be weaker than “fresh” thread. Think of the Steelhead or Shad colors that are only in high demand for certain parts of the year, and remain dormant in the rack for the intervening nine months. When needed next year they might be a bit weaker, and multiple years of storage will continue their decline. If you are plagued by weak thread that seems to break more than it should, remember sunlight is the enemy and both your storage and the vendor’s premises may be contributing to the issue.

Start with Danville 6/0 before moving smaller

I recommend most new tiers use Danville 6/0 thread to aquaint themselves with fine threads. Danville is a wonderful thread and a great starting point for a new tier. Later, once you’re accustomed to the 6/0 you can move down to the 8/0 Uni’s or Ultra Threads once you have skills using fine nylon thread. Thread choice doesn’t lend any “killing” quality to the fly pattern, it’s typically the choice of the meathead tying the fly, not an element that lends to the fly’s deadliness, so substitution of size, brand, or color, is not an issue.

Thread should be stored long term in opaque drawers out of direct sunlight. It’s fine to store active spools on your bench, just don’t leave them there for months at a time.

While thread is considered the enemy, it has more uses than most tiers imagine

Fly tier’s routinely ignore the properties that make thread something more useful. I’ve watched tiers painstakingly select a shade of dubbing for a fly body, or admire an imitation next to a real bug in alcohol, pronouncing how this season … they have finally developed the perfect imitation of the [Insert_Latin_Name_Here], and how they will no longer be denied victory on their favorite creek or drainage.

… and they completely ignore thread and water, despite both being present in every fishing scenario…

Simply put, the thread color can add itself into the overall body color of the fly when wet, especially on lighter colored flies, most of whom are dry flies. Many fly tying videos and fly patterns specify black thread, and this can affect your imitation in the worst way. Light colored flys, will have a muddy appearance as the fly becomes saturated, not at all the color the tyer originally envisioned. As black is among the most common colors purchased, once damp your perfect imitation of the local bug turns into a darker version, and may in part be responsible for a lackluster reception by fish.

The above pair of pictures show a Creme colored dubbing dubbed with four different thread colors. Black, Fluorescent Orange, Light Yellow, and Light Olive, all Danville 6/0 colors. The dry version shows a nice creme hue regardless of thread color, and the dampened version shows how both the Black and the Fluorescent Orange can bleed through the lighter colored dubbing and alter the overall appearance of the fly. Both the neutral colors, Light Yellow and light Olive show less, if any, color bleed.

Matching thread to the imitation, or simply adding a translucent effect

Tying lighter colored dry flies should always be done with neutral colored thread, tan, light gray, light yellow or light olive. These should be the colors most used by the tier for overall fly tying. Blacks and browns are fine on darker flies or nymphs, and specialty flies like Shad, Saltwater, or Steelhead, may require brighter hues given those flies are typically ALWAYS attractors versus a realistic imitation.

As every fly tier ever created goes through an exacting imitation phase … thread color and color bleed through will be extra important on flies tied to imitate a specific insect. Translucent effects can also be tailored to a specific bug wherein the fly body dubbing is chosen to facilitate thread color bleed through, and you can add a tint to the result using the thread color. Saturated light colored dubbing turns into a translucent gel allowing the thread color to bleed through agressively, as shown in the below photograph.

Above is the female Little Yellow Stone (#16) we use on Hat Creek. There are many variants of the fly, using yellow deer hair and other high floating materials, but this is the version I have used for many years. Rather than dubbing two colors of dubbing on the body, I simply start the fly with Hot Orange Danville 6/0, and switch to the yellow thread once I have finished the dubbed Yellow fur body. I put a pronounced band of hot orange hread at the rear to bleed through the yellow and imitate the egg sac, then dub the remainder of yellow body and rely on the bleed when damp to make the egg sac visible.

Threads can be used to tint as well as to overpower dubbing colors. Neutral colors will offer a hint of color, bolder colors will offer much more depending on the choice of body color. The combination of thread color and damp dubbing can add a dimension of translucence to lighter flies that mimic the squishiness of the original. Whether the fish care is immaterial, as it’s the angler’s confidence in the killing properties of his bug that determines success and failure.

In summary, thread use and colors can be as much a science as other forms of fly construction. Use the neutral colors of thread to preserve the coloration of the dry insect when damp, use more pronounced thread colors and light colored dubbing to “tint” the damp fly body with thread color, and use agressive thread colors to make bug parts pop out, as needed.

… and make sure ALL threads are stored in dark closets or drawers to preserve their color and strength in perpetuity.