AHello everyone, I've searched (Google) for answers to my question and nothing that helped came up from Cake Central or anywhere else, so I have to start a new thread.

I recently had to make dark green buttercream icing. I used a tried and tested recipe, and Wilton gel colour (Kelly green). I made it as I normally would, but after I started spreading it onto the cake, the colour started to kind of split and go a marbled white/green colour. It was quite a hot day and I don't have air con in my kitchen, so I am wondering if it was because it was too warm?

Thanks for reading :)

AWell hmm not quite sure but it for one donuts like the icing wasnt mixed together all the way ( once a icing is colored a color not sure if it can become white again) you don't say what kind of icing that you are using? Is it a buttercream shortening using shortening in the recipe? Or is it a different kind of icing? I Owen wilton gel colors but am slowly switching to americolor they carry them at hobby lobby and other cake supply stored. I just like them better , they come in alittle squeeze bottle thus you don't have to dig into the jar to get the needed amount of color. Anyways icing a cake in a hot kitchen would for sure cause for difficulty in icing it I can see the shortening seperating or melting not crusting up due to it being so hot. That might be the problem shortening just down right melting. But I'm stumped once the icing has been mixed completely thurolly and there is no white color left I don't know how it would marble? All I can imagine is the whole batch of icing being a hot mess and the oils in the shortening just not agreeing with the gel paste. It was just to oily to mix completely? I don't know just a guessing game for me too. Was your gel Color old not sure if that would matter or if your shortening was old still not sure if that would matter. Was your icing completely already made before you added the color? Hmmm a mystery. Hopefully someone here will know the for sure answer

AOh reresding your post you do say what kind of icing you were using still I just don't know. Last week there was a thread on here where a lady's icing was seperating from the warmth of her hands. Did you use cold milk or water to make your icing? Maybe that caused a problem warm shortening with ice cold liquid maybe it caused it to separate? Nope I don't know

AOk I googled it and found an old post from here it basically says that wilton gel paste colors are water based and the shortening is oil so because it was hot the water and oil separated. They suggested using high ratio shortening ( I swear by the stuff) and using an oil based coloring they didn't say any brand names on that and I'm not sure what brands are oil based. They also suggested two other things 1. Whip the heck out of your icing to get it to mix and 2.add either some more sugar to the icing recipe or cornstarch to it to thicken up the recipe they did not give amounts of how much to add. They also suggested trying a different icing recipe

AI googled.... why would color separate in cake icing

Most recipes for buttercream icing have enough water to disperse the gel when it is mixed for long enough.  I use both Wilton and Americolor, cannot tell the difference.

But a "buttercream" that has only shortening and sugar will for sure streak with a gel colour.  

If you cannot add water to your icing, then add corn syrup/glucose or a smaller amount of glycerine or pipng gel and mix again for a few minutes at low speed.

The only time I've ever had a problem with color beading up and not getting incorporated into the buttercream was when I used a meringue buttercream and a very bright color. The oil in the buttercream must have been too much for the color, which was probably water-based. If you use candy colors that are oil-based they sometimes work better, or powdered colors.

I've ever had that happen when I use confectioner's sugar buttercream, but in a hot kitchen it could happen, I suppose.

I wonder if the icing crusted a bit or even where the hot kitchen air set the color on the top of the bowl of icing (y'know how icing gets darker after it sits a while) and then when you applied it to the cake the different colors did not re-blend together because they had set up with the heat. Perhaps.

For what it's worth icing made with milk holds color better especially the pink shades. Just a thought for next time.