Don’t use warm water? The first recipe I made royal icing with called for warm water and I think it came out great, but the truth is, I never got any explanation for either why to or not to use it. What temperature do you use? I only cook with filtered tap water and we keep our Brita in the fridge so it would be refrigerator temperature unless I warmed it up some. I typically microwave it for about 30 seconds to get it to room temperature or slightly warmer.