I'm not a big fan of American BC so I usually avoid it in favor of cream cheese frosting, SMBC, etc. I've recently had to make American BC (butter, powdered sugar, vanilla, cream/milk) for others and have been experiencing a weird problem. When I color the BC (with paste colors), I notice the frosting looks kind of shimmery (like an oil slick). Then when I look closely, it looks as if something in the buttercream has separated. I've seen truly "broken" BC and I don't think this is the same. From a distance, my buttercream looks ok and you may not notice the issue I mentioned. Anyway, I'm trying to figure out how to prevent this and would love some help. My theories place the blame on either (1) butter that's too soft OR (2) the effect of acidic ingredients (lemon juice or a little cream cheese). I'm sorry if this has already been covered and I'm rehashing it. Please point me to the previous thread if that is the case. Thanks!

XL