I am having a problem with my royal icing and am trying to figure out if it happen to everyone else. I put my RI (Antonia 74's recipe) in my pastry bags, do my first layers and go to continue working the next day. However, the RI has started to separate overnight (liquid forming in an area). I sometimes can knead it together in the bag, but often have to take it out, remix in a bowl, pop the bubbles, clean the bag and reload. I am losing tons of time. Does this happen to anyone else or do you not store it overnight in the bags to start with?
This happens to me too, though not all the time... Maybe it has to do with the consistency of the icing - thick vs. thin??? I'd be curious to see what other people say. Thanks for the great question!
For me it's happened more with the thinned out icing and darker colors. To prevent this from happening I put it in the fridge still in the bags soon after I'm done for the day. It seems the longer it sits at room temp the more likely your icing will do this. You'll still have to knead it a little but not nearly as much as when you let it sit at room temp. HTH.
It's going to separate (eventually.) You should remix/ re-beat the icing to get it back to proper consistency. If it's in a bag you can tie off the end and cap the tip and knead really well.
Okay, so it looks like it is not just me! I'll try the fridge idea (thanks bakinccc!), bring to room temp and knead as neccessary. I used to do the fridge idea, but stopped and it seemed fine, but not so much any more. I might also be too heavy on my use of coloring as I like deep colors.
Thanks for the affirmation that it wasn't just me! I spent 2 hours the other day unloading, remixing, stirring to get out bubbles, washing bags and tip and finally (!) reloading the 13 colors I was using. I about lost my mind! 
Sounds like the nature of the beast. Thanks from me too for all the input.
Yes...thinned royal will separate into three distinct layers when left to sit.
Untinted, the top layer is fluffy/spongey/marshmallowy, the middle is a pale yellow runny liquid and the bottom is thick/dense/solid.
I wouldn't store royal icing in bags, intending to use them the next day or two. The separation process will indeed start within this time frame. If you are making it up beforehand, store it in a clean air-tight Tupperware container or even still in the mixing bowl (with a slightly damp tea-towel laid overtop and a plastic grocery bag over the entire bowl to prevent drying/crusting.) The benefit of these storage methods is that you can indeed give it a tiny beating to restore it to the right consistency AND leaving the pre-made thinned icing overnight gets rid of most of those tiny pesky air bubbles in the icing....making it smooth as glass when you do go to use it! 
Kneading the bag won't really get it back to that exact consistensy either. You'll have to give it some good stirring in either the mixer again (less than a minute) or by hand with a spatula/wooden spoon.
My best advice is to just bag it as you are about to pipe it, but not for storing. 
As a Wilton Instructor I tell my students not to store the royal icing in the bags.
When I went to a training session for us Instructors we were told not to keep the royal icing stored in the bags over night but to put the icing back in it's bowl for storing so that if separation happens we can then mix it back together.
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