howto create glass test tubes with semi-transparent fluid content I want to create some glass test tubes with semi transparent fluid content of some different colors. I'd like to see through test tubes on ones behind. There should be no scene background (transparent) and glass should be semi-transparent. Output is RGBA PNG

I know I have to set Transparent checkbox in Render -> Film.
I found this for glass:
how to render semi-transparent objects with transparent background as a png with cycles

I don't know how to make fluid content to be as realistic as possible.

It should be in cycles.

Is there any solution for light not only as world surface to have effect on objects?
I've tried to composite three layers:


Glass material:


Fluid material:


Not ideal, but the best output I achieved for now:


I don't know how to make glass material brighter.