The colormax has a bad reputation for being very cracky... both thermally and after annealing. I don't have cognac, I have the white, and it's a very pretty translucent white. Unfortunately, because colormax are notorious for making incompatible COE glass, you cannot use this with any other boro, or each other, without risking cracks long after annealing.
I have been using the white for single color spacers... but it's very slow to melt and takes a long time to shape. I do like the color white, which reminds me of milk glass, but because of the incompatibility potential, it's best use is alone. In marbles, the colormax white will become translucent, so not a good marble color either.
But as I have a need for a lot of white spacers, I'm happy with it for that purpose
.
A really nice white that's very compatible and buttery to work with (but worthless in marbles) is borostix white. It's less expensive than the colormax too.