How Do I Prevent This Material From Glowing in the Darkness?

It really depends how you have your lighting set up. Some questions:

  1. Have you built light? ( you will probably find it descends into darkness when you do that )

  2. Do you have a dynamic or static / stationary directional light or skylight. Often skylight can do this kind of thing, in which case you can make it dynamic and reduce it’s intensity.