About adding soy: I really like the aesthetics and the burn of a parasoy that is around a 50/50 blend. To that end, I’d try adding 15-20% soy to get there. It will have a creamier look and better adhesion. But it will also come with it’s own set of problems. At that % of total soy there is a possibility of frosting, especially if you are using solid dyes. You’ll likely find a diminished HT with certain FOs, while others (vanillas and bakery mostly) will be richer. Colors won’t be as quite as vivid. You may also need longer cure times. The burn will change, but if the wicking is off or other factors, you will still get black soot. CT may be stronger.
With 6006 alone, the jar definitely shouldn’t be black. If that’s what you’re getting, something is wrong in the system. CD wicks can work very well in 6006, but like any wick, they can cause soot if it’s too big OR too small. Is the wick self-trimming? Mushrooming? Are you using dye? If it’s heavily dyed, you might want to try one without dye to see if there is a difference. Any number of things or combination of things could be causing excessive soot. I’d be happy to help you troubleshoot.