"Shieldz" over dry-wall compound -- dry-wall compound is coming off

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

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.
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I couldn't say for sure, but perhaps the joint compound needed to be primed first before applying any other coating to it. Try contacting the manufacturer.
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On Sunday, July 10, 2016 at 9:44:21 AM UTC-4, John G wrote:

Except that he says it's the drywall compound that is apparently lifting off the drywall board at the tapered edges, not the paint lifting off. Plus I thought Shieldz was a primer. IDK, I've never seen this happen. If you don't remove all the dust from sanding, that could affect the paint not sticking, but if it's actual pieces of drywall compound coming off, IDK. What kind of drywall compound was used?
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On 07/09/2016 2:25 PM, Percival P. Cassidy wrote:

Dunno'; never used the product. The Tech Data sheet doesn't say anything terribly much on new drywall; does say plaster must cure 90 days before using the product. I'd guess the two days wasn't long enough, but I'd contact Zinnser and ask what happened/how to fix/prevent.
<http://www.rustoleum.com/~/media/DigitalEncyclopedia/Documents/RustoleumUSA/TDS/English/CBG/Zinsser/SHZ-02_ShieldZ_Universal_Wallcovering_Primer_TDS.ashx
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My guess is that the water base Shieldz transmitted enough water to the thin areas of compound to turn it back into its original state. If that is so, I wouldn't expect it to fall off though, just stay where it is and dry again.
A coat of shellac before Shieldz would solve the problem.
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On Sunday, July 10, 2016 at 10:20:08 AM UTC-4, dadiOH wrote:

Drywall compound is not supposed to turn back into it's original state with the application of some water, certainly not with the amount of water in some primer that dries in 15 minutes. AFAIK, it's like concrete, ie it undergoes a reaction and it's not simply water going out and it's ready to accept water and return back to original. The problem seems to be with whatever the joint compound used was and/or the condition of the drywall board. We don't know what kind of compound, board, etc. New or had they been sitting around, surface possibly soiled, etc?
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On 07/10/2016 9:50 AM, trader_4 wrote: ...

That's a good point; it's quite possible _any_ water-based primer would've resulted in the same result if the problem was really one of adhesion only...which isn't a bad supposition; one would presume the product itself doesn't cause rampant such failures or wouldn't be around...while I think Zinnser is one of the "pretty proud of themselves" products in general, they generally do perform.
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trader_4 wrote:

You're wrong on this one Trader_4 , regular drywall compound WILL dissolve with water . The fast-setting types won't , they're as you say a plaster-type set .
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On Sunday, July 10, 2016 at 11:06:27 AM UTC-4, Terry Coombs wrote:

Well, I did include this part:
"is not supposed to turn back into it's original state

I know it's not totally hard forever like concrete, but I thought from experience that when it's dried on tools it's been a pain to get off, even when scrubbing and using hot water. But it does come off at least under those conditions with some work, so maybe you're right, with enough water and enough time, maybe it will go fully plastic again. But the water exposure the OP had is very minimal and if what's happening is normal, then you'd have that problem with any latex paint, right?
I just started a test. I knew where there were a couple globs of it left on a piece of cardboard from a home project here. I took two small pieces, they are soaking in water. I'll check at 15 mins, see what happens and continue.
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On Sunday, July 10, 2016 at 11:47:03 AM UTC-4, trader_4 wrote:

I missed the 15 min check, but at 30 mins the two pieces had softened up and working them between my fingers, I did get it back to consistency similar to original. These were about nickel thickness flat pieces. It was the pre-made, normal dry speed stuff. So it does soften up a lot more easily than I thought. But obviously this shouldn't be the problem the OP is having, because if the minimal water in latex paint can cause it to come off, everybody would have the problem.
I'm left thinking it's something to do with either the mud used or the surface of the board, which we have no info on.
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You could try redoing the drywallcompound, and then extra dry it using a he ated hair dryer. You could also use the hair dryer to dry whatever type of oil-based primer you put on over the drywall compound before using anythin g related to water on the patches.
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