Is there a way I can make a hollow object solid? Yesterday i managed to create this shape that is similar to a teardrop.

Front view:


Side view:


I then mirrored it on the Z axis using the mirror modifier like this:

But the shape is hollow from the inside and that creates a problem when I render it as glass, because instead of passing through a solid object, the light simply passes through 2 glass planes.

Is there a way to create a solid object from a hollow one ? I haven't been able to find a sort of "Fill" function that does that.
You can just use the soldify modifier. This lets you change the thickness and tweak it later on.