Glass

With this little tutorial you'll create this:

Modeling

1.Define a spline like this

2.Select these two points and right click to convert to smooth

3.Add a lathe modifier define on min

You must obtain something like this:

4.Go back to the line level and select the spline level

5.Select outline and decrease of 0,1 (one click on the down arrow)

6.Go on the segment level and delete this segment

7.Go up to the lathe modifier. Check the weldcore and flip normal boxes and increase the number of segment to 40.

You can improve the shape by convert some points to Bezier corner and play with the handles.