On Sat, 9 Jul 2016 15:25:16 -0400, "Percival P. Cassidy"
wrote:

I repaired some holes in a wall that is to be wallpapered, and then
started applying "Shieldz" to provide the proper surface for the
wallpaper -- and now, an hour or so later, I find that the drywall
compound is lifting up and falling off at the nicely tapered edges. The
dry-wall compound has had a couple of days to dry.

What have I done wrong?

Perce

I'm not familiar with this product, since I dont use wallpaper. However,
it seems to me that if this product was applied according to the
instructions, then your joint compound was not applied properly. Joint
compound will come loose and fall off if the wall is saturated with
water, but should not come off from giving it a coat of paint or
applying anything that gets it slightly wet for a brief period of time.