On my model I have red areas on the grey texture. I accomplish this by adding a 2nd texture and using an RGB curve to single out the dark red only.
I would like to get the red areas as you can see below, to glow as if they where hot.
Using Emission in place of the Diffuse BSDF for the 2nd texture:
I've tried adding emission in there, but it seems to just increase the amount of red over the surface of the rock, and cranking it's strength up increased the amount of red though the brightness stays about the same. I want to keep the amount of red the same, but make it seem as if it where hot and giving off light.
Edit: There is a pretty large chance that I'm going about this completely wrong though.