I use the CD wicks and have about 6 scents that soot. It does not matter what size jar, wick, fragrance amount, color or not, or whether they are single or double wicked. After months of pulling my hair out, someone told me (can't remember who) that there are times when a scent with vanillan will do that. A couple of them were vanilla scents and a few had vanillan in with the spice blend. The last was one that had a miniscule amount of vanillan, even so that you could not detect it. But it seems that the vanillan was counteracting with some of the other ingredients and caused the sooting. Now that was over a year ago, before my shoulder surgery, and I have not tried those fragrances since. But I would be very interested to know what other results you get. I got so frustrated that I refused to even make the scents, even in melts, for a while!!