How, if at all, does the color of black thread change change if CP is not used?

Not any, really. Black is black. In fact, if anything it would be an even deeper and darker black without CP.

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I don't think the color changes at all. Black is black, period. I've been using Chromaseal and it seems to coat the thread to give it a continuous "tape" look rather than seeing each individual thread. Some like that look others don't.

Chromaseal when applied to black doesn't leave any white flakey residue as others do.

I`ve just built a rod using black thread,did`nt use any CP and as tom said it went a deeper shade of black.Actually it came out fantastic,very pleased with it.

Does the chromaseal darken colored threads like Madeira?? CP always takes the threads about a 1/2 shade darker or so.

When using black thread (Gudebrod) use regular thread not the NCP. The NCP black thread vary often will have a purplish tint to it. Some years ago I thought my eyes were playing a game with me but I found out from other rod builders that they saw the same thing. There is no need to use NCP black as it is completely opaque in the regular.

Thank you, Gentlemen