Butter seeping into icing

I won't be much help with the recipe part (as to why its happening) but I'm thinking maybe instead of a glaze, painting on a thin smooth layer of RI, letting it dry then decorating? So you'd have a full royal icing barrier. That would take extra time but might help. do you use a dehumidifier and keep your shop air conditioned? Those might help also. 

I have had that happen before.  I live in coastal South Texas - lots of heat and humidity!  I start drying on racks in air-conditioned room with two oscillating fans constantly running over the cookies until the cookies are packaged. It stopped happening when I stopped drying on a shelf located directly under some high intensity inset canister lights...they produced an inordinate amount of heat right down on the cookies.  Has never happened after I started drying on cooling racks under fans!  When I'm decorating I also lower the a/c 3-4 degrees lower than we usually keep the house.  Hope that helps.

Thanks for your answers!

In France, places with air conditionning are very rare and I don't have that in my work kitchen nor at home. My work kitchen is rather fresh at the moment, we will see if it lasts(it is 91° F today outside).

The problem is when I deliver cookies or ship them, I have a wedding next week and I'm affraid the cookies are going to wait in a place with no air conditionning.

I could try putting a royal icing layer but RI is porous so I don't think it will stop the butter to go through.

I have had it happen with royal too, but if I use a small fan directly over the icing, it sets up fine and does not bleed through later no matter how warm it gets.
I would give royal with a fan a try,;o)

Ali, thanks, but I'm allready fanning my icing, it like it shiny.

I was wondering if it is because I use a recipe with no baking powder, as I find the cookies keep they shapes better this way?

People in France don't know sugar cookies, if I give them a white, soft cookie they ask me if it's underbaked

So I make crunchy golden "sablés" but as the ingredients and the proportions are the same than in sugar cookies, I don't think this is the issue.

ParrsPantry, yes our cars are cooled, mostly, and lots of people have air conditionning at home but annyway, it would be impossible to ensure that my cookies stays in a cooled environement at any time.

I live in NJ where it gets very humid.  I have had this happen to my icing before too.  I realized it happened when I decorated my cookies the same day I baked them.  I now bake the day before I want to decorate to help this problem.  After I decorate I put them under a fan.  So far it hasn't happened again.

Thanks Jennifer, I know it's not my issue either, I rarely have the time to bake and decorate the same day...

It gets so frustrating because I've examined some cookies I brought to a market last week, it was very hot and many cookies are stained, but not all and I haven't got a clue to why... Especialy a big, white one which is pristine!

the only time this happens to me is when I stacked my cookies and put them in a container before I ice them. If I bake cookies today and I'm not going to flood them until tomorrow, I'll put them in a container with parchment sheets in between each layer. Haven't had the problem since.

Thanks Jill for your tip,I generaly try not to stack them, I'll try both ways and I'll see...

A little update: I've finaly found some kind of solution: I've switched to glaze!

I made some test cookies, some with royal icing and some with glaze, and I exposed them to the sun. The results: the RI turned yellow in a few hours, the glaze stayed white and spotless.

I think this is because RI is porous and absorbs the butter.

I won't use glaze for everything, though, flooding with glaze is a real pain... in the hand!

You could try switching your brand of meringue powder. I had terrible problems with my icing blotching when I was using Wilton MP, but haven't had any since switching to Henry & Henry (same as CK I'm told).

Thanks Jaclyn, I don't use meringue powder, I use organic powdered egg white.

I could try with meringue powder, but it would be a french brand obviously... It would be interesting to see if it makes a difference.