I've bought this varnish after putting up beautiful wallpaper a few months ago. The hallway had a vinyl paper originally and now it's ordinary wallpaper. As soon as the cold nights started, I noticed condensation marks forming on the new paper just above the front door. Gutted doesn't start to describe it! I cleaned as much as I could and then coated the paper with this varnish. To be honest I've decided in the spring to take the paper off and redo it but I will immediately apply this varnish in the hope I get no more condensation problems. I can say this varnish leaves no residue whatsoever and is completely invisible. I just wish I had know about a) the condensation issue and b) known about this varnish!
Thank you Sian Zeng for being available via a Google search.