Transparent fluid

Hi,

I have successfully created a scene with a fluid simulation, turning a character into fluid. I have a problem with the material. Before turning to fluid, the character has a glas material an the things behind are seen through. When I turn the character into fluid which uses exactly the same material the transparency is gone. The fluid looks like mercury and nothing behind it can be seen any more.
Where I’m doing wrong?

Greetz,
Cpt