For myself these moments are just another opportunity knocking.
However, opportunities always come with the possibility of failure.
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Thus I try to approach new materials with a bit of critical thinking.
So lets break it down:
1. Do I have a plan on how I can first use the material?
I won't buy a material without at least one use for the material in mind already. Often tying with the material will inspire other applications. Think Jujubee midge .
2. Do I just need one or several colors?
This goes back to the planned application. I'll give a real life example.
I recently picked up some of Fly Fish Food's Bruiser Blend dubbing. I knew I wanted to use it to make a head on a baitfish pattern and use in a similar fashion to Senyo's laser dubbing. Knowing this I can assess the usual colors I make my baitfish patterns and purchase those: White, black, grey, chartreuse, olive, cream.
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Alternatively I might need only need a specific color to represent a certain feature on a fly that I have been working to prefect for a while.
After playing with the bruiser blend for a while I discovered that its length and fluid nature would be ideal for crawfish claws. Always keep your eye open for unseen potential with fly tying materials.