I've trailed through all the 'my buttercream is separating' threads but a question I didn't come across... I've just made some BC and added royal blue colouring gel, (it says for BC) and its separating. I leave my butter out once its open, but its quite hot and there was some oil in the tub so that shows how soft it was, could this be the reason its separated? I think majority of the times i have coloured it this happens.

I used double icing sugar to butter

Try creaming your butter for a longer period of time and see if that works.

AWhat kind of butter are you using? From your description it sounds like either margarine or the soft butters (such as the Land O'Lakes with olive oil in a tub) that have oil in them. If so, that could be ther problem; the seem to have a low melting point.

AStork usually. That's what I use for my sponge and its always really nice so just use that for BC too. Just looked at stork and its only 59% VEGETABLE fat! Think I might buy PROPER butter, looked at that was 80% milk fat. Could that be where I'm going wrong?

AYes.

What kind of BC?

Try placing it back in the fridge for 10 minutes and beating it.

Thanks for your help.

Bought some real butter today, coloured it and it hasn't separated. One problem now. I don't really like the taste. I bought Sainsbury's own butter because it was cheap and this was just a test to see for myself.

I'm in the UK, so what to people here use for buttercream? I had thought about Lurpak? 

AI'm glad you were able to make it work with real butter. Try again with a higher quality butter. I'm sorry, I'm in US so don't know what brands you would get. Also, the stuff in the tub you were using probably has some salt, so that would affect the flavor. You could try adding a bit of fine salt and see if that helps improve the flavor for you.

AAre you using any flavoring like vanilla, almond, etc?

I used unsalted but spoke to my mums friend tonight and she said she uses salted Lurpak so Im gonna try that.

Yeah I added vanilla extract. :)

When I make buttercream (cold-process "American" BC, from the recipe that's been on the back of the C&H powdered sugar box since before most of us were born), I use plain store-brand salted butter, which, in the U.S., is invariably churned from sweet cream.

If you're using unsalted, either try salted butter, or add salt yourself.

If you're using salted with a recipe that adds salt, try leaving out the additional salt.

If you're using butter made from fermented cream, try using butter made from sweet cream.

An odd observation I made, some time ago: the margarine we use at home, for both cooking and table use ("I can't believe . . ."), is actually more expensive than the store-brand butter we use for (again) both cooking and table use. (And despite the name of the product, I can tell almost instantly if somebody grabbed the wrong stick [we serve butter in a glass butter dish, and margarine in a plastic one], usually before it gets within a foot of my mouth.) And as I recall, the vegan, dairy free margarine I bought some time ago for a single batch on the "wood type cookie" project is even more expensive.

(Incidentally, for sauteing the onions and celery for turkey dressing, I've started using a 50/50 mix of unsalted butter and salted margarine. And for sauteing Rice-a-Roni, I've taken to using a 50/50 mix of salted butter and Canola oil.)