I would like to know something more about Tiffen’s ColorCore® technology. Is the core of the filter made of gel or is it glass?

The Tiffen ColorCore technology is a secret proprietary formula so we cannot tell you the exact composition of the material used. However, most Tiffen filters are laminates, which has the advantage of providing uniform color and density even after the filter is polished to our exacting specifications. This system has proven extremely reliable and consistent over many decades of filter production