I don't use fondant too often, but I am doing a cake that needs a few different colors of fondant(Batman cake). To save money, I would prefer to buy white Satin Ice and color it with the colors I need. I have read that Americolor is the best, and I am wondering if it will give me a true black color. How much will I have to use? A few drops, a whole bottle, multiple bottles? I just need to make sure I get enough.

My advice would be to buy black Satin Ice. I don't think you could knead in enough color to make a true black. If you only want to buy white, then I would suggest that you paint the fondant with Black Americolor airbrush paint. I've done that several times and it's always worked out perfectly.