Help with Materials

I am trying to make a glass cup with a cylinder and I made it transparent and everything but when I got to smooth it, it turns partially black I think it’s ![emiss.PNG|690x357]
because of the emission but I tried changing it but it makes it glow the color I change it to. Any ideas?

If you are not using an HDRI and your World background is dark or black, what colour do you expect to see?

Idk, I’m new to Blender and last time when I watched Blender Guru’s tutorial to make a glass cup this did not happen. (idk what HDRI is)

An HDRI, in laymen’s terms, is like a giant sphere around your scene that has a high dynamic picture of an environment. You can get some at HDRI haven website.

What john means: You have a light in your scene, but the environment is (as good as) black. For example, imagine you are in space, where there is one lamp and one plane. The rest is black. You look through the glass. What would you see?

But also, and that might be what you are looking for: when you smooth your object, turn on auto smooth in Properties panel > Object Data Properties > Normals > Autosmooth (checkbox).

Here is what happens when you have a cylinder, inset and extrude that top face inward, shade it smooth without auto smooth:

Why don’t you use the glass shader instead of the principled shader?