Cove-ert problem

[PerranOak]

So, they've put up the coving and there were a few irregularities with adjoining pieces.

They used filler and I sanded the join. However, the coving seems to be made of paper on a thin layer of card over plaster!

Now I have exposed the card with my sanding.

How should I proceed? I need to sand the joins otherwise they will look very poor. do I need to prep the "cardboard" in any special way before painting?

Cheers.

 

[Wayners]

Gardz all the coving.
Just seals it including sanding damage.
Use a wide blade, plastic or metal and smooth over any damaged surfaces or joints.
240 grade sand.
Fill again if needed.
Spot prime filler with gardz.
Emulsion.
That's how I do it now.
Few years ago is mistcoat cove.
Fill
Sand
Spot mistcoat filler.

Some call the filling blade a busker.
I used a 150mm scraper or something similar like a spatz to fill