Changing Opacity of Meshes.

Probably not the most difficult question here, but I’m a new to working with materials. I’m trying to make an mesh in my scene decrease in opacity when I press a key. I have the MarterialParameterCollection setup (I’ve tried with both a scalar and a vector parameter, none of which fully work for me). In the actual material, I get the parameter and hook it up to the opacity option. The issue comes when I try to render the mesh at full opacity, it renders in some value between 0-1. I’ve tried additive and translucent blend modes, but both still don’t render with 100% opacity when the value is one. Any ideas as to what my mistake could be?