Problem plastering over jointing compound - it wont stick

[showl]

Hi,

Trying to skim plaster my first ceiling but have run into a problem. The plaster isn't sticking to the joint compound.

The ceiling is made up of 2 pieces of plasterboard. I jointed the 2 boards using self-adhesive mesh jointing tape and then Blue Hawk jointing compound. Then left for at least 24 hours to dry (one bit was an entire week).

Using Thistle Board Finish plaster, which seemed fine and adhered to the board as expected BUT where I've skimmed over the joints the plaster is literally peeling away from the joint compound, taking a fine layer of the joint compound with it.

Anyone know why this would be?

Am I missing a step, did the joint compound need some kind of sealer or PVA or something?

Any help gratefully appreciated!

Steve.

 

[PrenticeBoyofDerry]

There was no real need to apply jointing compound, the joint tapes would have been good enough, unless you had large gaps between joints.
Not familiar with Blue Hawk products. If it acts the same as easi-fill, it can be quite chalky and take in moisture. So sounds like you have encountered suction/adhesion problems. So the advice I would give, is seal the joints with PVA (two coat application)