Why does my ceiling look patchy after three coats of white emulsion?

Likely that it didnt look like that before because it had been painted with a flat matt white paint. Typically a paint for new plaster when first painted. Im guessing youve now painted it with a vinyl matt emulsion. That wont be truly flat matt and will have some sheen level albeit low. But any sheen level will bounce light and as you say viewed from a certain angle you will see the imperfections. These were caused when the ceiling was origionally painted ( poor application and considerarion given to how absorbent the plaster was) rather than anything you have done. Common occurence

Hello, There may be a few of issues. If there has been any water damage leaving behind water staining these can be problematic to solve. you my need to apply a damp/water stain proofing primer to the patchy areas and the repaint the whole ceiling. If you have had the ceiling plastered the paint may have been applied before it is fully dry or the plastering may not have been done well resulting in patchy shadows when moving around the room, or could be paint application. On ceilings to avoid patchy areas I will paint 3 coats. One in one direction, the second coat 90 degrees to the first and then finally third coat back in the same direction of the first. This will result in an even paint coverage. Hope this helps. Kind regards Surinder Bahel Apex Properties Services

It could be from historic issues or quality of paint used. When rolling ceilings the direction should be alternated between coats. Alternatively you can spray paint ceilings to give an even finish.

I would seal the patches with a oil based undercoat, this would be better applied with a small fibre or foam roller making sure you spread the oil paint evenly which will improve the surface ,then you need to apply a Matt emulsion ideally crown cover matt as this does not contain vinyl and will help disguise the underlying problem