AHello... The movie frozen has got me interested in sugar work. I have only made one batch of sugar glass at home.. Sugar,corn syrup, tarter and water. It turned out well but I am wondering if it ever gets completely solid. It seems to stay somewhat flexible. Is isomalt a better choice? I am wAnting to make a ice castle plaque to attach to fondant.. I am afraid that it would get sticky and soften if I put it on buttercream. Any tips would be appreciated.

I took a pulled sugar class where we made several flowers and bows and the sugar got hard quickly, make sure you are getting to the right temperature.  What is nice about using sugar rather than isomalt is when you serve the cake the sugar plaque could be broken up and served with each piece of cake.  The downside is you can make the pulled sugar ahead of time and wrap it very tightly but you don't want to make the plaque too far ahead of time since the sugar will start breaking down.  Would be best to make the morning of.

That being said, although I haven't used isomalt, the advantage with it is that it will hold its shape and not break down like sugar.  You can make it well in advance.  But it isn't something you want anyone to eat.  Although it is food safe, I understand it isn't very tasty.  Similar to fondant and gumpaste, although gumpaste is food safe, it's not intended for consumption.

Sounds like a cute cake.  Be sure to post a picture when you finish it!