Greetings, LQ. Since upgrading from 16.04LTS to 18.04 I am having a strange issue with transparency with Urxvt. The same problem occurred in Mrxvt and aterm, but those two are now removed. I plan to add mrxvt again after solving this problem.

I am using the 18.04 with Gnome and both gnome terminal and Eterm have transparency/shading working properly. When I open Urxvt with transparency the shading value has an unusual effect. When shading is 100 the background is transparent with no shading effect. When <100 the background is solid gray, and when >100 it is solid white. I also have Fluxbox on this laptop and the same thing happens there.

The computer is a HP G50 series laptop with Intel 4500M graphics Rev.07, using the i915 driver according to lspci -v. I also have a HP mini 110 series laptop running Xubuntu. After upgrading to 18.04 the mini does not have the same problem.

urxvt can use both real and fake transparency.
i never use it, but it might have something to do with what you're experiencing.
i'm sure gnome is using real transparency, so maybe try to eradicate all fake transparency URxvt settings.

1 members found this post helpful.

Thanks, ondoho. The tip about Gnome using real transparency pointed me in the right direction. I found that my .Xresources included settings for both real and fake. According to the man page, when both settings exist the fake is used. As you suggested, I removed the fake transparency settings and problem solved