Keith (Dorset) wrote:
It could be a thin layer of emulsion over distemper as it's an old house
(c`1840)

Oh, messy. A cheap flat pan scourer (not too abrasive), with warm
water and a bit of sugar soap (or washing-up liquid). In a day or
two you will have a nice clean ceiling. Anyone know a better way
to wash off distemper?