Control opacity of glass?

How can I control the Opacity of the glass material? I want to make it sort of see through like this:



I want to show fluid inside the container (fluid will be a blue mesh) but I want the container to be about 20% see through.

 

AFAIK, you could use a semi-transparent texture to do this.

 

ok cool thanks! So that texture can be on layer 0 right? or does it have to be on a separate layer?

 

not worth the extra polies/texture space for the blue in my opinion. Better off making it a solid white container.

 

True it would reduce some draw calls