I had the same problem adding CO. I bought mine from C&S 76 degree. The tops of my candles had a shiny, harder top to them. In testing, I pour the wax let it set up then poke holes to put the wicks in. If they don't work I melt the top down evenly, pull out the wicks, let the wax set back up and poke one or two more holes to try a different wick(s). When I poke the new hole(s) the wax sometimes does crack from around the wick hole and I've had a few crack to the side of the glass. When I pour containers I already have the wicking issue figured out and not poking new holes, I still get the shiny, hard tops. Without the CO, I don't have that problem. I worked with it quite awhile trying to get rid of the hardness because it does help with the hot & cold throw. I use gb 444........using less CO or more CO doesn't seem to change the issue. I live in cold WI ....maybe that has something to do with it. Just wanted to add my 2 cents of experience on the CO thing...HTH