Problem with glass material and lighting it in cycles

I was following this tutorial to render a glass bottle with some jet red liquid inside it and the final render is as under

I’ve described the problem in the image itself. Jonathan described something similar in the tutorial like

The inner surface of the glass jar and the outer surface of the liquid is the same and hence you will either see dark liquid or artefacts Hence we need to remove the inner faces.
But I seriously dint get what he was talking about. Hence I’ve turned to BA.

I am attaching my blend file for ref - Liquid Bottle.blend (652 KB)


Your model looks like his, maybe you are just needing to adjust your lighting. Also, maybe you need to adjust the IOR of your fluid material. It helps to name your materials as you make them, since a large file can contain hundreds o fmaterials.

While sides of your liquid object have correct normals pointing inwards, top is not - normals here should point outwards.
Liquid object bottom should be positioned more above “ground” level leaving gap for what would be glass there.
From the modeling point of view liquid top should meet with glass inside; you have them overlap.

another problem i see is that your liquid don’t have a top!

you could add some bubles inside

and the glass thickness is not equal
better copy you bottle sode and scale it down then seperate it or assign new mat for liquid
at least it would give a constant width for the glass thickness

but still looking good

happy cycles