finishing a fly rod for daughter. the butt wrap looks ok until a black streak appears. have cut off wrap, cleaned with acetone and wrapped again twice the finish is a lite flex coat . should I try a new bottle of flexcoat , cut it off and try again? any idea what is the cause.

Is the black streak in the finish or the thread? It sounds to me like an area where you did not apply color preserver. A missed swipe with the brush perhaps.

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looks to be in finish. thread is a dark green and I use 2 coats of color preserver

I'll assume you do not thin the color preserver. I'll also assume you're not flaming the finish.

Something has to be getting into the finish by means of your brush.

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never thought it might be the brush . will throw away get a new one and redo finish. thanks for input

sounds like it could be a single bristle from the brush. I only use top quality Sable brushes for my finish. They don't loose and of their bristles.

the flaw looks like ink . thought maybe the finish was affecting the rubber butt I have used similar items and finishes w/o problems. the finish is a couple of yrs old

It's unlikely to be the epoxy - it doesn't go bad, unless you manage to get something into it.

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A picture would probably help with the diagnosis on this.