I am wrapping with white thread, and wanting to know if a white sharpie to color the blank underneath the wrap will keep the white thread color white?

Lorenzo,
Take a test blank and give it a try.
Often, when you write with a sharpie you get color transfer, so if you want to do it, be sure to test first.

Roger

Roger what is color transfer?

Also Roger, would cp keep the white thread white, if wrapped over a dark blank, or should i color the blank white before wrapping the white thread?

Wrapping with white over a dark blank is a tuff one.
Transfur is when you use a marker or ball point pen and then wrap over it it will bleed through, maby CP will stop but do a test.
I just finnished a rod with white thread and did a under wrap with 2 coats of CP and then the top wrap and dubble CP and it was nice and white.

You can wrap silver metalic under white or mask of area painters tape light coats of Krylon fusion or Mudhole ncp white alone with cpl coats of cp will work well.

Lorenzo, Some of the ways I have done it over the years: silver foil tape, white paint, White Out, white shoe polish, Createx auto air brush paint in base white.The air brush paint is a water base type but, must be set with heat. After you paint the area just set it with a heat gun or hair drier. I never had a problem with any of these applications. Remember, anything you have to do to keep the blank from showing thru your light colored wraps without fisheyes. Test wrap and finish on scrap to make sure you got it down right.

Dennis J. Danku
(Sayreville,NJ)

Some years ago I solved this problem for myself by taping of the handle and above where the wrap will end and spraying the blank with Krylon Fusion paint, let dry overnight and wrap over it. This works on closed wraps and is not as bulky as a thread under wrap. My light colors stay true this way. It obviously won't work on an open wrap, but can if you choose to have the lighter painted open sections show. I've done this and it can look quite nice. I have never had a problem with the paint cracking etc.