plaster advice

around a month ago i plastered a kitcken wall for my folks. the wall was uneven so i used thistle hardwall as an undercoat after sealing the wall with pva, then applied the plaster after another wet pva coat. Left this to dry over night then the next day again i sealed the wall with pva again and skimmed the wall with multfinish over another coat of wet pva.
came back after a few days and noticed a few hairline cracks. i damped the cracks with a wet sponge and the cracks have shrunk. going to apply a little filler and sand, should look ok.
came back after a month to do some more work on the room and after inspection of my previous work. ive noticed that alot of the wall sounds hollow when i tap on it. mainly the part of the wall i plastered last. the parts where the cracks were sound fine.
i am wondering if the tacky pva i used before skimming/scratch coat dryed before i got to that part of the wall?
i wished i used thistle bonding instead of hardwall, is this right?
should i have not sealed the scratch coat with pva?
should i leave this wall as it is and paint it. or ive heard that it is possible to drill a small hole in the plaster and inject some pva into it to bond the plaster.
any advice on this whould be great!! i have three more walls to do round there.
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Sterling, I know someone who has done this with pva on a 10inch repair that went hollow and it worked. Whethet it is ok for a large surface remains to be seen and I would be interested in the outcome. He may have had the same problem as you as he had applied a damp prood paint under the repair and I wonder if this affected the adhesion. Best of luck.
Stu http://www.cateringappliancesltd.co.uk
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is it worth trying to inject pva in between the plasters? any ideas on why it has cracked in some places? about 40% sounds quite hollow when tapped. Not so hollow atm so that it sounds like it will fall off.
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