Splotchy Corn Syrup Glaze (aka Confectioners' Icing)

I had the same issue with glaze icing. I've only used it once, and I used it over a coat of (dried) royal icing. I was going for a stained glass look. The splotchy spots appeared while drying and I don't think it was due to butter bleeding because I had a layer of RI between the cookie and the glaze. I posted the question here but unfortunately didn't get an answer. I didn't bother with glaze icing again. I've attached a pic of the cookie with the issue, tried to paint over the whole mess to cover it up without much success. Sorry can't be of more help. 

Are you talking about straight-up corn syrup thinned with a little water? Or confectioner's icing with a little corn sryup in it?

Julia, I'm talking about the powder sugar version with corn syrup.  It's probably confectioner's icing but I've always called it corn syrup glaze.

It could be recrystallization of the sugar (though the corn syrup is added to prevent this), or discoloration caused by differential drying of colors.

I only use glaze to ice my cookies and I was having problems with splotches too

I was adding water to thin out my icing when it was too thick and I often would have splotches later on. Not sure if that is why or not but I stopped thinning it with water and I haven't had a problem since--Could it be not mixing the icing thoroughly enough?

What do you thin the icing with?  Corn syrup, milk,....?  Thanks!

I've done both and haven't had any problems either way

I use corn syrup glaze.  Toba Garrett's recipe with milk.  Never had any problems with splotches.

Might have to try milk.  Does a person need to be concerned about the milk spoiling or would there be enough sugar to prevent this?  I use water and the splotchy look generally happens the next day after the icing is dry.

I know this is an old question, but I just discovered this site.  I got the splotches, too, when I first started.  Now I always add white food coloring to my glaze before adding another color... it makes the glaze opaque and I have never again had problems with splotches.

Great tip!