Selection For Perfection

Thursday, 13 January 2022  |  Sarah

Thread:
Selection Process
Characteristics
Twisted or Untwisted?

Selection Process
Most fly dressers select thread purely based on thickness/denier (8/0 or 70 denier for example).  This necessarily isn’t a bad think as when tying small flies it makes sense to chose a finer thread, like Semperfli 18/0 classic waxed for example.  Of course, when tying pike / predator, or saltwater patterns then we’d aim for a thread at the other end of the spectrum, like Semperfli classic waxed 6/0, or even 3/0.
Characteristics
Just as important however, are the characteristics of a given thread and by that, we mean the way it behaves during tying.
Multi-fibred thread like Semperfli Classic waxed thread in 12/0, 8/0 & 6/0 only have a slight twist, so this lies flat (open) in its unused state, unlike Uni Pre-Waxed which is bonded and twisted, giving a more rounded profile.
The advantage of untwisted thread is an even layer of thread is easily achieved. Which enhances the final look of your flies.

Thread that lays flat has a greater surface area, making it ideal for securing materials like foam and deer hair that won’t be sheared off due to the increased surface area.

That said there are times when a tightly twisted thread is required, as possessing a round profile this has less surface area. 

Instances where this might be necessary are when winding through palmered hackles to protect them
Now, a rounded thread traps less hackle fibres. 

Equally, when we come to complete the fly with that all important whip finish a rounded thread does not fray and ‘ball-up’ on itself, which can occur with thread that lies flat.
This of course doesn’t mean that a thread which principally lays flat is rendered useless.  In fact quite the opposite is true as by spinning your bobbin holder in a clockwise direction (when viewed from above) actually tightens the thread to make it round in profile. 

Conversely, to take tension off again for you thread to lay flat, simply spin the bobbin holder in the opposite direction (anticlockwise).
Why Bother With Twisted Threads?!?
The answer really is nothing more than on certain patterns like north country spiders or those solely using thread bodies (the Gel Body Buzzer for example) a pre-twisted thread gives you the required and strength profile without the need to start spinning your bobbing holder. 

Furthermore they remain in a twisted state at all times of the tying process.

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