I would say it is a MUST to PVA over the "hydrochroma" if its same as Supermatt...
Most Fillers Fall Off when used on Supermatt ! Now there is food for thought !
PVA the night before Plastering ! Try applying pva and once "dry" then for a test, sprinkle some water on the "dry" pva and watch what happens.
What happens is the PVA turns back to tacky pva ! The same happens with plaster when applied to "dry" pva.
Therefore why apply plaster when pva is...
ALL depends on surface to be painted...
Dulux Trade has the BEST vinyl soft sheen but not vinyl matt...
Dulux Trade has the best oil based gloss...
Leyland has the best vinyl matt...
However, Dulux Trade has best colours....
Choice is yours....
RICH MATT CANNOT be used on bare plaster.......
I am amazed its still going on........
http://www.diydoctor.org.uk/forums/viewtopic.php?t=17500&sid=8abc0ba2216493b6ffb8524dbc1420a1
THE BEST WAY to deal with your situation is:
Dry scrape ALL loose material
Apply a coat of ThistleBond-It bonding agent
Then TWO coats of multi-finish plaster.
The plastic will ALWAYS take ages to dry regardless of what you put on them.
One way to get rid of this prob is to apply the Ames Taping Corner Bead on top of your corners.
Wet the matt emulsion 3 times (2 mins at each stage of wetting) then slightly scrape off with an scraper whilst taking care not damaging the previous applied silk.
Once finished as advized above, rub down the silk getting rid of sheen.
Then apply Leyland Vinyl Matt (Magnolia).
You will...