What else can I use to thin my buttercream besides milk? Letting a cake with milk in the frosting sit out very long makes me nervous!

I usually just use water... I just put in a few drops at a time until I get the right consistency.

water

something should make you nervous based on facts, not just how you "feel". Sugar is a stablizer, reducing the water activity that causes spoiling. Scientifically, the sugar and milk stablize each other. This has nothing to do with how I "feel" about it ..... it's a scientific fact and this is how it works.

I use milk in my icing. I store my icing on the counter. It's fine.

You CAN use water to thin your icing. I personally dont' prefer that. Reminds me of my mom mixing water and powdered sugar (and that's ALL she mixed together) to make the crappiest tasting icing in the world.

our mothers and grandmothers had cakes sitting on the counter for days and it held up fine, even those covered with icing made with milk and butter. I often wonder how we went backwards in our thinking on some of this stuff.

Sugar is hygroscopic (water absorbing) so it controls the water activity of liquid ingredients used in your American b/c recipe. (Will only work when amount of liquid is small and amount of sugar is large.)

Water activity & microbial growth:
(Prolonging Bakery Product Life.)

http://tinyurl.com/6fbkcz

WJ Scott in 1953 first established that it was water activity, not water content that correlated with bacterial growth:

http://tinyurl.com/bmsato

Formulating for increased shelf life:
(Decreasing water activity results in hostile environment for bacteria.)

http://tinyurl.com/csu2b9

HTH

No one said that water was the only other ingredient used in the icing. My customers love my icing and I do use water instead of milk. I used to use milk, but like this recipe better. Everyone has there own way and opinions and that doesn't mean they are wrong if they don't do it the way you think they should. Milk has it place also. Thinning down icing works fine w/water. It takes such a small amount. I have been doing it for over 40 years and it seems to work fine, so I don't know.

Does anyone know how long BCD can be kept in the fridge?

You can use corn syrup also.

This is a useful post as I too was a bit concerned about using milk especially for young children as I thought it might go off, i didnt know that about the sugar etc...