A game of "Snakes and Ladders"
So, the next step was to start painting the ceiling and walls but this soon exposed a new problem. The undercoat/primer I'd just sprayed the ceiling with bubbled in a few places, including the small area at top left of image 1, and as I scraped them back the new layer plus two older layers came away far too easily and cleanly, leaving what appears to be an oil-based layer over the original dark green milk paint layer. Image 1 shows several square feet that were stripped in just a couple of minutes. No heat was used, just the tool shown in image 2.
At that point I decided to strip the entire ceiling and start again with a properly prepared substrate. The oil paint layer (possibly a linseed oil based paint) is very well bonded and can stay.
1. A problem
2. This tool really works
3. Ceiling stripped
4. Three layers of ceiling paint on the floor
Notes on the ceiling cracks
In image 3, the lighter coloured areas adjacent to some cracks (esp. to the right of the ceiling rose) are filler used to feather the slight ridges created by the cracks. I don't know when this was done but it appears the cracks have not got worse since.
There were the following identifiable paint layers on the ceiling at the start of renovations:
1) Dark green (milk paint) - 1880
2) Beige (oil paint - possibly white when new) - date unknown
3) White (acrylic) - assuming 1983
4) Pale green (acrylic) - assuming 1983
The filler was applied prior to layer (3) and so I assume this was done in 1983 when the rooms were last renovated. If so, that indicates that the ceilings have not deteriorated further over the past 38 years, and possibly much longer than that.
This is a pressed metal rose installed over the original oil lamp smoke vent. It was tacked and glued to the ceiling so that the outer flange left a raised edge that was now looking rough. I've decided to feather this edge to blend it into the ceiling.
The outer flange can just be seen in image 5, after three layers of plaster compound and lightly sanded back.
Prep and Painting
After feathering cracks and other rough areas it was time to apply a primer. I chose a shellac based primer to go over the existing oil based surface and to block any stains that might emerge, as they did in bedroom 1. This was applied by brush.
It was then time to spray my chosen top coat colour (Dulux Stowe White matt) to the crown and the ceiling. The Dulux Stowe White I used in the annex loft appears darker in these south-facing rooms. However, I like the colour more than a stark untinted ceiling white so I've gone halfway between and redone it all with Taubmans Tradex Ceiling paint tinted Taubmans Inner Circle (a close match to Dulux Natural White).
I like the Taubmans Tradex Ceiling paint because it appears even flatter than the Dulux matt, which was a washable wall paint.
5. Ceiling rose - feathered
6. Top coat sprayed to crown and ceiling