The finest solution would be "Fade" from the "&" menu. But that is destructive. So please duplicate the to-be-faded layer first and hide it.
Thanks! i will check it out!
Just tried it and checked out the tutorial on fade. Have to say it's pretty fiddly. And quite often the app was very unresponsive (maybe my phone). I noticed Russell that PS "doesn't use masks". He's probably thinking of Blender or apps like Photo Wizard, which do use masks, and which do this a lot better with a lot more control. Love PS Touch but this probably isn't its strong point.